RD06 secondary metabolites against filariasis causing Culex quinquefasciatus and statistical media optimization for larvicidal derivatives production

Mosquito-borne disease pandemics, such as the Zika virus and chikungunya, have escalated cognizance of how critical it is to implement proficient mosquito vector control measures. The prevention of Culicidae is becoming more difficult these days because of the expeditious imminence of synthetic pesticide resistance and the universal expansion of tremendously invasive mosquito vectors. The present study highlights the insecticidal and larvicidal efficacy of the prospective novel actinobacterium derived from the marine Streptomyces sp. RD06 secondary metabolites against Culex quinquefasciatus mosquito. The pupicidal activity of Streptomyces sp. RD06 showed LC50=199.22±11.54 and LC90= 591.84 ±55.41 against the pupa. The purified bioactive metabolites 1, 2-Benzenedicarboxylic acid, diheptyl ester from Streptomyces sp. RD06 exhibited an LC50 value of 154.13±10.50 and an LC90 value of 642.84±74.61 tested against Cx. quinquefasciatus larvae. The Streptomyces sp. RD06 secondary metabolites exhibited 100 % non-hatchability at 62.5 ppm, and 82 % of hatchability was observed at 250 ppm. In addition, media optimization showed that the highest biomass production was attained at a temperature of 41.44°C, pH 9.23, nitrogen source 11.43 mg/ml, and carbon source 150 mg/ml. Compared to control larvae, the histology and confocal microscopy results showed destruction to the anal gill, lumen content, and epithelial layer residues in the treated larvae. Utilizing an eco-friendly method, these alternative inventive insecticidal derivatives from Streptomyces sp. RD06 eradicates Culex quinquefasciatus. This study highlights the promising potential of these Streptomyces sp. RD06 secondary metabolites to develop affordable and efficacious mosquito larvicides to replace synthetic insecticides in the future.

(Piperaceae) and its majority compound β-caryophyllene: mechanism of larvicidal action against Aedes aegypti (Diptera: Culicidae) and selective toxicity

Synthetic insecticides have been the primary approach in controlling Aedes aegypti; however, their indiscriminate use has led to the development of resistance and toxicity to non-target animals. In contrast, essential oils (EOs) are alternatives for vector control. This study investigated the mechanism of larvicidal action of the EO and β-caryophyllene from Piper tuberculatum against A. aegypti larvae, as well as evaluated the toxicity of both on non-target animals. The EO extracted from P. tuberculatum leaves was majority constituted of β-caryophyllene (54.8%). Both demonstrated larvicidal activity (LC50 of 48.61 and 57.20 ppm, p < 0.05), acetylcholinesterase inhibition (IC50 of 57.78 and 71.97 ppm), and an increase in the production of reactive oxygen and nitrogen species in larvae after exposure to the EO and β-caryophyllene. Furthermore, EO and β-caryophyllene demonstrate no toxicity to non-target animals Toxorhynchites haemorrhoidalis, Anisops bouvieri, and Diplonychus indicus (100% of survival rate), while the insecticide α-cypermethrin was highly toxic (100% of death). The results demonstrate that the EO from P. tuberculatum and β-caryophyllene are important larvicidal agents.

Biological activity of essential oils from Ferulago angulata and Ferula assa-foetida against food-related microorganisms (antimicrobial) and Ephestia kuehniella as a storage pest (insecticidal); an in vitro and in silico study

Misuse of synthetic pesticides and antimicrobials in agriculture and the food industry has resulted in food contamination, promoting resistant pests and pathogen strains and hazards for humanity and the environment. Therefore, ever-increasing concern about synthetic chemicals has stimulated interest in eco-friendly compounds. Ferulago angulata (Schltdl.) Boiss. and Ferula assa-foetida L., as medicinal species with restricted natural distribution and unknown biological potential, aimed at investigation of their essential oil (EO) biological properties, were subjected. Z-β-Ocimene and Z-1-Propenyl-sec-butyl disulfide molecules were identified as the major composition of the essential oil of the fruits of F. angulata and F. assa-foetida, respectively. In vitro antimicrobial activity and membrane destruction investigation by scanning electron microscopy imaging illustrated that F. angulata EO had potent antibacterial activity. Besides, the EOs of both plants exhibited significant anti-yeast activity against Candida albicans. In relation to insecticidal activity, both EOs indicated appropriate potential against Ephestia kuehniella; however, the F. assa-foetida EO had more toxicity on the studied pest. Among several insecticidal-related targets, acetylcholinesterase was identified as the main target of EO based on the molecular docking approach. Hence, in line with in vitro results, in silico evaluation determined that F. assa-foetida has a higher potential for inhibiting acetylcholinesterase and, consequently, better insecticide properties. Overall, in addition to the antioxidant properties of both EO, F. angulata EO could serve as an effective prevention against microbial spoilage and foodborne pathogens, and F. assa-foetida EO holds promise as a multi-purpose and natural biocide for yeast contamination and pest management particularly against E. kuehniella.

Oxidative stress induction by essential oil from Piper alatipetiolatum (Piperaceae) triggers lethality in the larvae of Culex quinquefasciatus (Diptera: Culicidae)

Culex quinquefasciatus is the main vector of lymphatic filariasis in Brazil, which present resistance to commercial insecticides. Nowadays, essential oils (EOs) exhibiting larvicidal activity, such as those derived from Piper alatipetiolatum, provide a promising alternative for vector control, including Culex species. This study aimed to investigate the larvicidal activity and the oxidative stress indicators of the EO from P. alatipetiolatum in Cx. quinquefasciatus larvae. The EO was extracted from P. alatipetiolatum leaves using the hydrodistillation method, resulting in a yield of 7.2 ± 0.1%, analysed by gas chromatography coupled with spectrometry and gas chromatography coupled with flame ionization detector (GC-MS and GC-FID), and evaluated against Cx. quinquefasciatus larvae. Reactive Oxygen and Nitrogen Species (RONS), Catalase (CAT), glutathione-S-transferase (GST), acetylcholinesterase (AChE), and Thiol levels were used as oxidative stress indicators. Analysis by CG-MS and CG-FID revealed that the main compound in the EO was the oxygenated sesquiterpene ishwarone, constituting 78.6% of the composition. Furthermore, the EO exhibited larvicidal activity, ranging from 26 to 100%, with an LC50 of 4.53 μg/mL and LC90 of 15.37 μg/mL. This activity was accompanied by a significant increase in RONS production, alterations in CAT, GST, AChE activity, and thiol levels compared to the control groups (p < 0.05). To the best of our knowledge, this is the first report describing the larvicidal activity and oxidative stress induced by the EO from P. alatipetiolatum against Cx. quinquefasciatus larvae. Therefore, we propose that this EO shows promise as larvicidal agent for the effective control of Cx. quinquefasciatus larvae.

Chemical composition and mosquitocidal properties of essential oil from Indian indigenous plants Ocimum tenuiflorum L. and Ocimum americanum L. against three vector mosquitoes

Mosquitoes stand out as the most perilous and impactful vectors on a global scale, transmitting a multitude of infectious diseases to both humans and other animals. The primary objective of the current research was to assess the effectiveness of EOs from Ocimum tenuiflorum L. and Ocimum americanum L. in controlling Anopheles stephensi Liston. Culex quinquefasciatus Say and Aedes aegypti L. mosquitoes. The larvae, pupae and eggs of the mosquitoes were exposed to four different concentrations (6.25-50 ppm). The tested EOs resulted in >99-100 % mortality at 120 h for the eggs of all examined mosquito species. It also showed robust larvicidal and pupicidal activity with LC50 and LC90 values of 17-39, 23-60 ppm and 46-220, and 73-412 ppm against Aedes, Culex and Anopheles mosquito species, respectively, at 24 h of treatment. The Suitability Index or Predator Safety Factor demonstrated that the EOs extracted from O. tenuiflorum L. and O. americanum L. did not cause harm to P. reticulata, D. indicus (water bug), G. affinis and nymph (dragonfly). GC-MS analysis identified the major probable constituents of the oil, including Phenol, 2-Methoxy-4-(1-Propenyl)- (28.29 %); 1-Methyl-3-(1'-Methylcyclopropyl) Cyclopentene (46.46 %); (E,E,E)-3,7,11,15-Tetramethylhexadeca-1,3,6,10,14-Pentaene (18.91 %) and 1,3-Isobenzofurandione, 3a,4,7,7a-Tetrahydro-4,7-Dimethyl (33.02 %). These constituents may play a significant role in the mosquitocidal activity of the oil. The same results were identified in the formulation prepared from the EOs. This marks the first report confirming the successful utilization of EOs derived from O. tenuiflorum L. and O. americanum L. in mosquito population control initiatives.

Evaluation of larvicidal potential of Eritrean medicinal plants against Aedes aegypti

Larvicidal activity of three Eritrean medicinal plants was evaluated against Aedes aegypti by conducting the bioassay using WHO methods. Efficacy of the plant extracts of O. hadiense, R. officinalis and C. spinarum was evaluated against 3rd instar Aedes aegypti larvae and mortality was recorded. LC50 and LC90 of the various plant extracts were also calculated using probit analysis. The morphological analysis of treated larvae was also performed. Extracts of O. hadiense, C. spinarium and R. officinalis were prepared using different solvents viz chloroform, 70% ethanol and water. Of the screened extracts, the chloroform extracts of O. hadiense exhibited the highest larvicidal activities and has the minimum LC50 and LC90 (24 mg/ml and 198.411 mg/ml respectively). Chloroform extract of C. spinarium exhibited the least larvicidal activity with maximum LC50 and LC90 (736.883 mg/ml and 1188.699 mg/ml respectively). Microscopic analysis confirmed the changes in the Aedes aegypti larvae caused by various plants extracts. An accumulation of dark pigmentation was observed in abdominal region and in the anal papillae after contact and also showed major structural damage such as destruction of the gut.

Exploring the bioactive potential leaves of Sphaeranthus indicus: Targeting immature stages of Aedes aegypti and Culex quinquefasciatus mosquito vectors through bioassay-guided screening and fraction isolation

Mosquito control is vital for combating mosquito-borne diseases, but concerns exist regarding the use of synthetic insecticides. This study aimed to explore eco-friendly alternatives derived from natural sources. The larvicidal, pupicidal, and ovicidal activities of various fractions obtained from the hexane leaf extract of Sphaeranthus indicus were investigated against two important mosquito vectors, Aedes aegypti and Culex quinquefasciatus. S. indicus leaves were extracted with hexane and column chromatography was performed with hexane, ethyl acetate, methanol, and their mixtures as eluents. Among the ten fractions (F1-F10) evaluated, fraction 'F-4' exhibited significant activity against third instar larvae, pupae, and eggs of both mosquito species, closely followed by 'F-5' . At a concentration of 10 ppm, 'F-4' achieved 100% mortality in larvae and displayed LC50 values of 5.08 ppm and 5.03 ppm for Ae. aegypti and Cx. quinquefasciatus larvae, respectively. The LC50 values for pupae were 6.12 ppm and 5.83 ppm for Ae. aegypti and Cx. quinquefasciatus, respectively. Regarding ovicidal activity, 'F-4' demonstrated percentages ranging from 63.2% to 64.8% against Ae. aegypti and Cx. quinquefasciatus eggs, respectively. These findings underscore the potent larvicidal, pupicidal, and ovicidal effects of fraction 'F-4' from S. indicus against the targeted mosquito species. Further research is warranted to identify the active compounds responsible for these effects and explore practical applications for sustainable mosquito control strategies.

Antibacterial, antibiofilm and larvicidal activity of silver nanoparticles synthesized from spider silk protein

Green synthesis of silver nanoparticles has gained attention due to its simple process of synthesis and varied applications. Scientists have tried its synthesis from a wide range of materials, but there is lack of reports that can use the metabolites of insects. Here in this study, we have used the spider silk protein which is considered as complete waste collected from household and field sources and processed to synthesize silver nanoparticles which were subsequently analyzed using different analytical tools like SEM, TEM, FTIR, and XRD. The spider silk protein-mediated synthesized nanoparticle (SP-AgNPs) showed a sharp peak at 420 nm when analyzed spectrophotometrically giving an indication of successful synthesis of AgNP. The synthesized nanoparticle ranges from 10 to 40 nm and were of varied shapes. The synthesized SP-AgNPs showed remarkable antibacterial activity. The MIC values against B. subtilis and E. coli were recorded 45 and 40 μg/mL respectively. Further to know the mechanisms of antibacterial activity protein leakage and conductivity measurement were conducted. The synthesized nanoparticle also showed excellent antibiofilm activity with inhibition percentages of 74 % and 68 % for E. coli and B. subtilis respectively at MIC concentration of the treatment. Finally, the synthesized nanoparticles was applied as mosquito larvicidal agent against Culex sp. and the difference between LC50 and LD90 value was recorded as statistically significant (p < 0.0267) during 24 h of incubation. Therefore, it can be said that spider-web could be an excellent biological reducing and capping agent for heavy metal nanoparticle synthesis that can minimize the ailments caused by mosquitoes and pathogenic microorganisms.

The high impact of zinc chromium oxide nanocombs on development of larvicidal and antimicrobial performance

Zinc chromium oxide (Cr/ZnO, 5wt.%) was prepared by a facile chemical co-precipitation route. The structure, composition, and chemical bonding were analyzed using X-ray diffraction (XRD), Energy dispersive X-ray spectroscopy (EDX), and Fourier-transform infrared spectroscopy (FTIR) indicating that chromium ions were integrated the host framework to form Cr/ZnO nanocomposite. Scanning electron microscopy (SEM) and Transmission electron microscopy (TEM) micrographs showed comb-shaped nanoparticles with an average size 20 nm and large surface area. The energy gap of the thin films was estimated from T% and R% measurements which exhibit a strong optical absorption edge close to the visible spectrum. The insecticidal activity of the synthesized nanocombs against C. pipiens larvae was evaluated with LC50 (30.15 ppm) and LC90 (100.22 ppm). Besides, the nanocomposite showed high antibacterial performance against gram-positive bacteria (Bacillus subtilis) and gram-negative bacteria (Proteus vulgaris) with inhibition zones 21.9 and 19 mm, respectively.

UPLC/ESI/MS profiling of red algae Galaxaura rugosa extracts and its activity against malaria mosquito vector, Anopheles pharoensis, with reference to Danio rerio and Daphnia magna as bioindicators

BACKGROUND

Anopheles pharoensis has a major role in transmitting several human diseases, especially malaria, in Egypt?. Controlling Anopheles is considered as an effective strategy to eliminate the spread of malaria worldwide. Galaxaura rugosa is a species of red algae found in tropical to subtropical marine environments. The presence of G. rugosa is indicative of the ecosystem's overall health. The current work aims to investigate UPLC/ESI/MS profile of G. rugosa methanol and petroleum ether extracts and its activity against An. pharoensis and non-target organisms, Danio rerio and Daphnia magna.

METHODS

Galaxaura rugosa specimens have been identified using DNA barcoding for the COI gene and verified as G. rugosa. The UPLC/ESI/MS profiling of G. rugosa collected from Egypt was described. The larvicidal and repellent activities of G. rugosa methanol and petroleum ether extracts against An. pharoensis were evaluated, as well as the toxicity of tested extracts on non-target organisms, Dan. rerio and Dap. magna.

RESULTS

The UPLC/ESI/MS analysis of methanol and petroleum ether extracts led to the tentative identification of 57 compounds belonging to different phytochemical classes, including flavonoids, tannins, phenolic acids, phenyl propanoids. Larval mortality was recorded at 93.33% and 90.67% at 80 and 35 ppm of methanol and petroleum ether extracts, respectively, while pupal mortality recorded 44.44 and 22.48% at 35 and 30 ppm, respectively. Larval duration was recorded at 5.31 and 5.64 days by methanol and petroleum ether extracts at 80 and 35 ppm, respectively. A decrease in acetylcholinesterase (AChE) level and a promotion in Glutathione-S-transferase (GST) level of An. pharoensis 3rd instar larvae were recorded by tested extracts. The petroleum ether extract was more effective against An. pharoensis starved females than methanol extract. Also, tested extracts recorded LC50 of 1988.8, 1365.1, and 11.65, 14.36 µg/mL against Dan. rerio, and Dap. magna, respectively.

CONCLUSIONS

Using red algae derivatives in An. pharoensis control could reduce costs and environmental impact and be harmless to humans and other non-target organisms.

Mosquito larvicidal, pupicidal and ovicidal effects of the extracts of Peltophorum pterocarpum flowers on Aedes aegypti and Culex quinquefasciatus

Mosquitoes are the vectors of several diseases like dengue, chikungunya, malaria etc. The three important mosquito species in India are Aedes aegypti, Culex quinquefasciatus and Anopheles stephensi. Several plant extracts have been tested for their anti-mosquito activity. In this dissertation, the larvicidal, pupicidal and ovicidal activities of the successive hexane, chloroform and methanol extracts of Peltophorum pterocarpum (Fabaceae) on mosquitoes are reported. The larvicidal activity of those extracts on both Aedes aegypti and Culex quinquefasciatus mosquitoes was found to be in a decreasing order of hexane, methanol and chloroform - the LC50 values for these extracts were 111.81 and 104.84 ppm, 121.92 and 121.56 ppm, 357.2 and 352.0 ppm respectively. Their pupicidal activity on both mosquitoes was found in the order of methanol, chloroform and hexane - the LC50 values for these extracts being 172.8 and 162.35 ppm, 425.8 respectively. Their ovicidal activity on both mosquitoes was found to be very low, even at the higher concentration of 500 ppm. This is the first report on the effect of the extracts of Peltophorum pterocarpum flowers on the two mosquito species of Aedes aegypti, Culex quinquefasciatus. In the present work, the results showed that the hexane extract had the highest larvicidal activity, while methanol showed the highest pupicidal activity besides larvicidal activity. Hence, the methanol extract holds promise to be used as mosquitocidal agent against the above two vectors.

Unraveling the Interaction Mechanism of the Compounds From Cladophora sp to Recognize Prospective Larvicidal and Bactericidal Activities: In vitro and In Silico Approaches

The present investigation aims to validate the larvicidal and antibacterial potential of Cladophora sp through in vitro and in silico approaches. The presence of phytoconstituents, functional groups and the compounds responsible for antibacterial and larvicidal activity were assessed through FT-IR and GC-MS analyses which unveiled the existence of active secondary metabolites, hydroxyl, alkane and carbonyl groups. The larvicidal and antibacterial activity of algal extract were examined and revealed complete mortality and substantial zone of inhibition was observed against Culex quinquefasciatus and E. coli. To support the in vitro investigation in silico studies were performed. Molecular docking investigations of the selected compounds from GC-MS which exhibited favorable agreement with drug likeness and ADMET properties indicated robust interactions with the larvicidal and bacterial proteins showcasing considerable binding affinities. Notably, 1,2,4-Oxadiazole, 3-(1,3-benzodioxol-5-yl)-5-[(4-iodo-1H-pyrazol-1-yl) methyl]- exhibited strong interactions with the target proteins. Density Functional Theory revealed that the energy gap of the lead compound was reduced and substantiates the occurrence of intermolecular charge transfer. Molecular Dynamic simulations confirms the stability and flexibility of the lead compound. Hence, this investigation offers computational perspectives on the molecular interactions of Cladophora sp, suggesting its suitability as a promising biocontrol agent.

Use of micro and macroalgae extracts for the control of vector mosquitoes

Mosquitoes are one of the most dangerous vectors of human diseases such as malaria, dengue, chikungunya, and Zika virus. Controlling these vectors is a challenging responsibility for public health authorities worldwide. In recent years, the use of products derived from living organisms has emerged as a promising approach for mosquito control. Among these living organisms, algae are of great interest due to their larvicidal properties. Some algal species provide nutritious food for larvae, while others produce allelochemicals that are toxic to mosquito larvae. In this article, we reviewed the existing literature on the larvicidal potential of extracts of micro- and macroalgae, transgenic microalgae, and nanoparticles of algae on mosquitoes and their underlying mechanisms. The results of many publications show that the toxic effects of micro- and macroalgae on mosquitoes vary according to the type of extraction, solvents, mosquito species, exposure time, larval stage, and algal components. A few studies suggest that the components of algae that have toxic effects on mosquitoes show through synergistic interaction between components, inhibition of feeding, damage to gut membrane cells, and inhibition of digestive and detoxification enzymes. In conclusion, algae extracts, transgenic microalgae, and nanoparticles of algae have shown significant larvicidal activity against mosquitoes, making them potential candidates for the development of new mosquito control products.

Biomonitoring of manganese metal pollution in water and its impacts on biological activities of Biomphalaria alexandrina snail and larvicidal potencies

Metal pollution has many dangerous environmental and human health consequences due to the bioaccumulation in the tissues. The present study aims to measure the bioaccumulation factor of the manganese (Mn) heavy metal in Biomphalaria alexandrina snails' tissues and water samples. The current results showed the concentration of Mn heavy metal in water (87.5 mg/l) and its bioaccumulation factor in Helisoma duryi tissue was higher than that in tissues of Physa acuta and B. alexandrina snails. Results showed that 87.5 mg/l Mn concentration had miracidicidal and cercaricidal activities. Also, this concentration decreased the mean total number of the hemocytes after exposure for 24 h or 48 h, while increasing both the mean mortality and phagocytic indices of the hemocytes of exposed snails. It caused alterations in the cytomorphology of the hemocytes of exposed snails after 24 or 48 h, where the granulocytes had irregular cell membranes and formed pseudopodia. Besides, levels of testosterone (T) and estradiol (E) were increased after exposure to 87.5 mg/l Mn metal compared to the control group. Also, it increased MDA (malonaldehyde) and TAC (total antioxidant capacity) contents, while decreasing SOD (superoxide dismutase). Besides, it caused significant histopathological damages in both hermaphrodite and digestive glands, represented in the degeneration of the gonadal, digestive, secretory cells, and the connective tissues. Therefore, B. alexandrina might be used as a sensitive bioindicator of pollution with Mn heavy metal to avoid ethics rules; besides, they are readily available and large in number.

Toxicity, repellency, and anti-cholinesterase activities of bioactive molecules from clove buds Syzygium aromaticum L. as an ecological alternative in the search for control Hyalomma scupense (Acari: Ixodidae)

Introduction

The goal of the current study is to evaluate the acaricidal and repellent properties of the ethanolic extract, essential oil, and primary component eugenol from Syzygium aromaticum against Hyalomma scupense cattle ticks. Their potential mechanisms of action were also examined, using an in vitro assay.

Methods

Clove essential oil was extracted using hydrodistillation technique. Gas chromatography-mass spectrometry (GC-MS) was performed to identify the chemical composition of clove. To evaluate the adulticidal, ovicidal, larvicidal and repellent proprieties of clove essential oil, eugenol and ethanolic extract on H. scupense, in vitro assays were performed using the adult immersion test (AIT), the ovicidal test, the larval packet test (LPT), the filter paper test and anti-acetylcholinesterase (AChE) activity.

Results

After treatment, eugenol, the primary phytoconstituent of clove oil, which accounts for 97.66% of the whole oil, had 99.22% acaricide activity and inhibited egg hatching at a concentration of 10 mg/mL. Eugenol and clove essential oil showed potent adulticidal effect at high concentrations (10 mg/mL), achieving 100 and 93.76% mortality, respectively. The ethanolic extract exhibited moderate activity. At high concentration, the larvicidal activity of S. aromaticum oil, eugenol, and ethanolic extract were 100, 100, and 77.18%, respectively. In filter paper experiments, when tested at the concentration 5 mg/mL; eugenol showed the longest repellent effect up to 6 h. We also found that eugenol was the most active AChE inhibitor (IC50 = 0.178 mg/mL). Nevertheless, additional investigations are required to confirm the accurate mechanism and the relevance of clove in practical application.

Conclusion

Overall, our research indicated that, because its effectiveness as acaricide, S. aromaticum essential oil and its phytoconstituent eugenol may offer an alternative source for the control of H. scupense cattle ticks.

Integration of ZnO nanorods with silver ions by a facile co-precipitation for antimicrobial, larvicidal, and ovicidal activity

BACKGROUND

Infectious diseases prompted by micro-organisms such as fungi, parasites, or microbes, have influenced many countries' public health causing death. Scientists declared that metal oxide composites have various advantages in the medical field such as the antimicrobial feature has freshly been revealed as well as its role in suppressing mosquito population.

METHODS

In this work silver doped zinc oxide nanorods (Ag/ZnO NRs, 10 wt.%) were prepared by simple chemical route, and their microstructural characteristics were investigated by XRD, EDX, SEM, and TEM techniques. The antimicrobial, larvicidal, and ovicidal of the synthesized nanocomposites were examined.

RESULTS

The synthesized nanocomposite exhibited binary phase of crystallite size 112 nm was calculated from Williamson-Hall method. EDX spectrum revealed the purity of the composite consists of Zn, O, and Ag elements. The SEM and TEM micrographs showed the particles in nanorods with high density on the surface. The energy gap [Formula: see text] was evaluated from the UV-Vis absorbance in the range from 2.90 [Formula: see text] 3.08 eV inside the visible spectrum. The antimicrobial activity of the nanorods was examined against Gram-positive bacteria (Staphylococcus aureus and Bacillus subtilis) with inhibition zones 10.5 and 14.5 mm, respectively. Whereas gram-negative bacteria (Escherichia coli, Salmonella Typhimurium, and Pseudomonas aeruginosa) were 14 and 17 mm, respectively. Further, Candida albicans was investigated with inhibition zone 7.5 mm. Besides, the insecticidal impact of the nanocomposite against Culex pipiens larvae was performed at 30 mg/l causing 100% larval mortality with LC50 (11.78 mg/l). The micrograph images showed deformations in the larval body as well as egg resulting in zero egg hatchability.

CONCLUSION

The findings approved that synthesized nanorods have a significant impact on controlling pathogens that impart different diseases to humans and the environment.

Larvicidal Effects of Metabolites Extracted from Nocardia and Streptomyces Species against the Forth Larval Stage of Anopheles stephensi (Diptera: Culicidae)

Background

Larvicidal agents can be produced using microbial resources, which are environmentally friendly, biodegradable, and economical. The study's goal was to evaluate the larvicidal activity of metabolites isolated from Nocardia (N. fluminea, N. soli and N. pseudobrasiliensis) and Streptomyces (S. alboflavus) bacterial species against Anopheles stephensi.

Methods

Four metabolites isolated from Nocardia and Streptomyces strains were exanimated for larvicidal activity. The experiments were performed for 24, 48, and 72 hours. 300, 350, 400, 450, 500, 550, and 600 μl of Actinobacteria metabolites were added to 100 cc of dechlorinated water. Fourth-stage larvae were placed in dechlorinated water as a control. LC50 and LC90 were calculated using toxicity data and analyzed.

Results

All metabolites had a statistically significant influence on mosquito larvae (P< 0.05). At 24, 48, and 72 hours, the LC50 for N2 (N. fluminea) was 417, 386, and 370 ppm, respectively, and the LC90 was 650, 595, and 561 ppm. Moreover, LC50 for N4 (N. soli) was 389, 376, and 347 and LC90 were 591, 565, and 533 and LC50 for N5 (N. pseudobrasiliensis) was 390, 357, and 341 ppm and LC90 were 589, 532 ppm. In addition, LC50 for S921 (S. alboflavus) was 484, 416, and 382 ppm, and LC90 was 701, 612, and 574 ppm.

Conclusion

The four bacterial metabolites tested in our study were found to have a notable effect on the mortality rate of Anopheles stephensi larvae, indicating their potential as natural larvicides. This is an effective technique for controlling Anopheles stephensi that has no detrimental environmental impact.

Seaweed Sargassum wightii mediated preparation of TiO2 nanoparticles, larvicidal activity against malaria and filariasis vectors, and its effect on non-target organisms

Malaria and Lymphatic filariasis are considered significant public health concerns in several countries. As a researcher, controlling those mosquitos using safe and eco-friendly insecticides is essential. Thus, we aimed to explore the potential use of seaweed Sargassum wightii for the biosynthesis of TiO2 NPs and evaluate its efficiency in controlling disease-transmitting mosquito larvae (using Anopheles subpictus and Culex quinquefasciatus larvae as model systems (in vivo)) as well as its potential effect on non-target organisms (using Poecilia reticulata fish as an experimental model). XRD, FT-IR, SEM-EDAX, and TEM carried out the characterization of TiO2 NPs. It evaluated the larvicidal activity against the fourth instar larvae of A. subpictus and C. quinquefasciatus. The larvicidal mortality was observed after 24 h of exposure to S. wightii extract and TiO2 NPs. S. wightii synthesized TiO2 NPs show excellent activity against A. subpictus and C. quinquefasciatus (LC50 = 4.37 and 4.68; LC90 = 8.33 and 8.97; χ2 = 5.741 and 4.531) mg/L respectively. The GC-MS results indicate the presence of some important long-chain phytoconstituents like linoleic acid, palmitic acid, oleic acid methyl ester, and stearic acid, among others. Furthermore, when testing the possible toxicity of biosynthesized NPs in a non-target organism, no adverse effects were observed in Poecilia reticulata fish exposed for 24 h, considering the evaluated biomarkers. Thus, overall, our study results reveal that biosynthesized TiO2 NPs are an effective and exciting eco-friendly approach to controlling the A. subpictus and C. quinquefasciatus.

Biosynthesis of copper oxide nanoparticles using Rubia cordifolia bark extract: characterization, antibacterial, antioxidant, larvicidal and photocatalytic activities

Rubia cordifolia represents the pivotal plant resource belonging to traditional Chinese medicine and Indian Ayurveda. The present study aims to synthesize biocompatible copper oxide nanoparticles (CuONPs) using R. cordifolia bark extracts, characterize the incumbent chemical transitions, and explore their biomedical and environmental applications. The absorbance peak between 250 and 300 nm clearly demonstrates the formation of CuONPs in the UV-visible spectrum. Fourier transform infrared spectroscopy results showed the presence of functional groups essential for copper ion reduction. Field emission scanning electron microscopy (FE-SEM) and dynamic light scattering analysis revealed that the CuONPs are spherical-shaped with a mean particle size of 50.72 nm. Additionally, the zeta potential demonstrates its robustness at 11.2 mV. X-ray diffraction pattern showed mixed phases (Cu, Cu₂O, and CuO) of cubic monoclinic crystalline nature. CuONPs exhibited noticeable antibacterial activity against Gram-negative (Escherichia coli and Pseudomonas aeruginosa) and Gram-positive (Staphylococcus aureus and Bacillus cereus) pathogenic bacteria. Bacterial cell damages were affirmed through FE-SEM imaging when treated with CuONPs. Further, CuONPs demonstrated considerable antioxidant activities by quenching free radicals such as DPPH (60.75%), ABTs (70.88%), nitric oxide (65.48%) and reducing power (71.44%) in a dose-dependent way. CuONPs showed significant larvicidal activity against Aedes aegypti (65 ± 8.66%), Anopheles stephensi (80 ± 13.69%), and Culex quinquefasciatus (72 ± 13.04%) mosquito larvae. The photocatalytic activity of the CuONPs demonstrates the methylene blue (81.84%) and crystal violet (64.0%) dye degradation potentials, indicating the environmental bioremediation efficacy. Hence the present study is the first report in accounting for the versatile applications of the phyto-CuONPs. Moreover, the green synthesis of CuONPS has future applications in designing the drug for life-threatening diseases and various environmental issues.

Larvicidal and pupicidal activity of phyto-synthesized zinc oxide nanoparticles against dengue vector aedes aegypti

This study aimed to assess the phyto-synthesizing potential of Tarenna asiatica methanol leaf extract as well as its larvicidal and pupicidal potential against Aedes aegypti larvae. According to the findings of this study, the methanol leaf extract of T. asiatica has the potential to synthesize zinc oxide nanoparticles from zinc acetate dehydrate. Standard analytical techniques such as UV-visible spectrophotometer, Fourier-transform infrared spectroscopy, X-ray Diffraction analysis, Scanning Electron Microscope, and Energy Dispersive X-Ray were used to characterize the phyto-synthesized nanoparticles. The zinc oxide nanoparticles synthesized ranged in size from 22.35 to 31.27 nm and was spherical in shape. These nanoparticles demonstrated excellent larvicidal activity against Aedes aegypti larvae in the second, third, and fourth in stars, as well as significant pupicidal activity. These findings suggest that the methanol leaf extract of T. asiatica synthesized zinc oxide nanoparticles, which could be used to develop mosquito repellents.

Evaluation of larvicidal enhanced activity of sandalwood oil via nano-emulsion against Culex pipiens and Ades aegypti

Mosquito control with essential oils is a trending strategy using aqueous oil nano-emulsions to expand their performance. Sandalwood essential oil and its prepared nano-emulsion used to estimate their larvicidal activities against the 3rd instar larvae of Culex pipiens and Aedes aegypti and their effects on larval tissue detoxifying enzymes. Sandalwood nano-emulsion was characterized by homogeneous, stable, average particles size (195.7 nm), polydispersity index (0.342), and zeta potential (−20.1 mV). Morphologically showed a regular spherical shape in size ranged from 112 to 169 nm that confirmed via scanning electron microscopy. Oil analysis identified sesquiterpene alcohols, mainly santalols, terpenoids, aromatic compounds, fatty acid methyl esters, and phenolic compounds. Larvicidal activities of the oil and its nano-emulsion indicated dose, formulation, and exposure time-related mortality after 24 and 48 h in both species. After 24 h, 100% mortality was detected at 1000 ppm for the nano-emulsion with LC₅₀ of 187.23 and 232.18 ppm and at 1500 ppm for the essential oil with an LC₅₀ of 299.47 and 349.59 ppm against the 3rd larvae Cx. pipiens and Ae. aegypti, respectively. Meanwhile, an enhanced significant effect of the nano-emulsion was observed compared to oil exposure in decreasing total protein content and the activities of alkaline phosphatase and β-esterase enzymes, and increasing α-esterase and glutathione S-transferase activities in larval body tissues. Results demonstrated the enhanced larvicidal potential of sandalwood oil nano-emulsion over that of oil. The effect involved alterations in the detoxifying enzymes based on the existing natural active ingredients against Cx. pipiens and Ae. aegypti larvae.

Sustainable development through the bio-fabrication of ecofriendly ZnO nanoparticles and its approaches to toxicology and environmental protection

Mosquito control is becoming more difficult as a result of the rise in resistance to toxic chemical insecticides. The insecticides of bio-fabrication sources may serve as a convenient alternative to environmentally acceptable methods in the future. The larvicidal and pupicidal activities of bio-fabricated zinc oxide nanoparticles (ZnO NPs) on the different instar larvae and pupae of Anopheles subpictus Grassi (Malaria vector) and Culex quinquefasciatus Say (lymphatic filariasis) were investigated in this study. The results recorded from XRD, FTIR, SEM-EDX, and TEM analyses confirmed the bio-fabrication of ZnO NPs. Such nanoparticles were nearly spherical and agglomerated with a size of 34.21 nm. GC-MS analysis of methanol extract revealed the compound, stigmasterol (C29H48O) as major one. Mosquito larvae and pupae of targeted mosquito were tested against varied concentrations of the bio-fabricated ZnO NPs and methanol extract of Vitex negundo for 24 h. The maximum activity was recorded from ZnO NPs against the larvae and pupae of A. subpictus LC50 which were 1.70 (I), 1.66 (II), 1.93 (III), 2.48 (IV), and 3.63 mg/L (pupa) and C. quinquefasciatus LC50 were 1.95 (I), 2.63 (II), 2.90 (III), 4.32 (IV), and 4.61 mg/L (pupa) respectively. ZnO NPs exhibited strong DPPH radical and FRAP scavengers compared to the aqueous extract of V. negundo. Also, V. negundo leaf methanol extract (VNLME) and ZnO NPs were evaluated for their cytotoxicity on HeLa cells, which exhibited the IC50 values of 72.35 and 43.70μg/mL, respectively. The methylene blue (MB) dye, which is harmful to both aquatic and terrestrial life, was degraded using the biosynthesized ZnO nanoparticles. At 664 nm, 81.2% of the MB dye had degraded after 120 min of exposure to sunlight. Overall, our results revealed that ZnO NPs are the perfect biological agent and economical for the control of malaria, filariasis vectors, antioxidant, HeLa cells, and MB blue dye degradation under sunlight irradiation.

Graphical abstract

Anthelmintic resistance in equine nematodes: Current status and emerging trends

Anthelmintic resistance is reported in equine nematodes with increasing frequency in recent years, and no new anthelmintic classes have been introduced during the past 40 years. This manuscript reviews published literature describing anthelmintic resistance in cyathostomins, Parascaris spp., and Oxyuris equi with special emphasis on larvicidal efficacy against encysted cyathostomin larvae and strongylid egg reappearance periods (ERP). Resistance to benzimidazoles and pyrimidines is highly prevalent in cyathostomin populations around the world, and macrocyclic lactone resistance has been documented in cyathostomins in recent years as well. Two recent studies have documented resistance to the larvicidal regimen of fenbendazole, whereas the larvicidal efficacy of moxidectin is variable, but with no evidence of a reduction from historic levels. In the 1990s, ERP estimates were 8-10 and 12-16 weeks for ivermectin and moxidectin, respectively, while several studies published after year 2000 found ERPs to be 5 weeks for both compounds. This is a clear change in anthelmintic performance, but it remains unclear if this is due to development of anthelmintic resistance or selection for other biological traits leading to a quicker resumption of strongylid egg shedding following anthelmintic treatment. Macrocyclic lactone resistance is common in Parascaris spp. around the world, but recent reports suggests that resistance to the two other classes should be monitored as well. Finally, O. equi has been reported resistant to ivermectin and moxidectin in countries representing four continents. In conclusion, multi-drug resistance is becoming the norm in managed cyathostomin populations around the world, and a similar pattern may be emerging in Parascaris spp. More work is required to understand the mechanisms behind the shortened ERPs, and researchers and veterinarians around the world are encouraged to routinely monitor anthelmintic efficacy against equine nematodes.

Anti-mosquito properties of Pelargonium roseum (Geraniaceae) and Juniperus virginiana (Cupressaceae) essential oils against dominant malaria vectors in Africa

Background

More than 90% of malaria cases occur in Africa where the disease is transmitted by Anopheles gambiae and Anopheles arabiensis. This study evaluated the anti-mosquito properties of Juniperus virginiana (JVO) and Pelargonium roseum (PRO) essential oils (EOs) against larvae and adults of An. gambiae sensu lato (s.l.) from East Africa in laboratory and semi-field conditions.

Methods

EOs was extracted from the aerial green parts of Asian herbs by hydrodistillation. Their constituents were characterized by gas chromatography-mass spectrometry (GC-MS). Larvicidal activities of JVO, PRO, and PRO components [citronellol (CO), linalool (LO), and geraniol (GO)] were investigated against An. gambiae sensu stricto (s.s.). The percentage of knockdown effects and mortality rates of all oils were also evaluated in the adults of susceptible An. gambiae s.s. and permethrin-resistant An. arabiensis.

Results

GC-MS analyses identified major constituents of JVO (sabinene, dl-limonene, β-myrcene, bornyl acetate, and terpinen-4-ol) and PRO (citronellol, citronellyl formate, L-menthone, linalool, and geraniol). Oils showed higher larvicidal activity in the laboratory than semi-field trials. The LC₅₀ values for JVO/PRO were computed as 10.82–2.89/7.13–0.9 ppm and 10.75–9.06/13.63–8.98 ppm in laboratory and semi-field environments, respectively at exposure time of 24–72 h. The percentage of knockdown effects of the oils were also greater in An. gambiae s.s. than in An. arabiensis. Filter papers impregnated with JVO (100 ppm) and PRO (25 ppm) displayed 100% mortality rates for An. gambiae s.s. and 3.75% and 90% mortality rates, for An. arabiensis populations, respectively. Each component of CO, LO, and GO exhibited 98.13%, 97.81%, and 87.5%, respectively, and a mixture of the PRO components indicated 94.69% adult mortality to permethrin-resistant An. arabiensis.

Conclusions

The findings of this study show that PRO and its main constituents, compared to JVO, have higher anti-mosquito properties in terms of larvicidal, knockdown, and mortality when applied against susceptible laboratory and resistant wild populations of An. gambiae s.l. Consequently, these oils have the potential for the development of new, efficient, safe, and affordable agents for mosquito control.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12936-022-04220-8.

Larvicidal activity and Histopathological changes of Cinnamomum burmannii, Syzygium aromaticum extracts and their combination on Culex pipiens

In order to develop an eco-friendly botanical larvicide alternative to the synthetic larvicides, extracts were prepared from the Cinnamomum burmannii (C.B.) and Syzygium aromaticum (S.A.) with hexane using a sonicator. The extracts were evaluated for larvicidal activity individually and in combination against the Culex pipiens larvae. The LC₅₀ value of C.B. and the S.A. hexane extracts tested individually were 184.2 and 363.7 µg/mL against Cx. pipiens respectively. All the combinations of the extract of C.B. and S.A. showed synergistic factors higher than one. Among the different ratios of extracts, the SA25%: CB75% extract was found to be more toxic than the other combinations (LC₅₀:125.7 µg/mL). Midgut cells treated with S.A. 25%: C.B. 75% extract showed severe morphological alterations such as degradation of microvilli; degeneration of epithelial cells, and peritrophic membrane; loss of nuclei, irregular and damage of microvilli. The extract has a promising larvicidal potential against Cx. pipiens, However, the extract was toxic against HUVEC cells, as evident from MTT and cell morphology. Further investigation is required to assess the toxicity of the extract on aquatic animals.

Essential oil as a new tool for larvicidal Aedes aegypti: A systematic review

OBJECTIVE

The study aimed to describe the effectiveness of essential oil plants for Aedes aegypti mosquito vector control.

METHODS

This systematic review selection process following with 2015 Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) Guideline. The source of the articles from databases international journal were Scopus, Pubmed, Scinapse and Google Scholar.

RESULT

Natural control management with essential oil is the way of alternative for larvicidal mosquito control especially A. aegypti. The essential oil for many plants can use for larvicidal against A. aegypti as Piper batle L., Tinospora rhumpii, Azadiractha indica, Persea americana, Piper aduncum, Leucas aspera, Eucaliptus camaldulensis, Ottonia anisum, Salvia Plebeian, Lantana camara, and Syzygium aromaticum with 100% mortality larvae A. aegypti at 48h.

CONCLUSIONS

The vector borne diseases must be used to integrate vector management control with essential oils plants.

Polyphenolic extracts from pomegranate and watermelon wastes as substrate to fabricate sustainable silver nanoparticles with larvicidal effect against Spodoptera littoralis

The agricultural wastes adversely affect the environment; however, they are rich in polyphenols; therefore, this study aimed to employ polyphenol-enriched waste extracts for silver nanoparticles synthesis, and study the larvicidal activity of silver nanoparticles fabricated by pomegranate and watermelon peels extracts (PPAgNPs and WPAgNPs) against all larval instars of Spodoptera littoralis. The polyphenol profile of pomegranate and watermelon peel extracts (PP and WP) and silver nanoparticles was detected by HPLC. The antioxidant activity was estimated by DPPH, and FARP assays and the antimicrobial activity was evaluated by disc assay. The Larvicidal activity of AgNPs against Egyptian leaf worm was performed by dipping technique. The obtained AgNPs were spherical with size ranged 15–85 nm and capped with proteins and polyphenols. The phenolic compounds in silver nanoparticles increased about extracts; therefore, they have the best performance in antioxidant/reducing activity, and inhibit the growth of tested bacteria and yeast. The PPAgNPs were the most effective against the first instar larvae instar (LC₅₀ = 68.32 µg/ml), followed by pomegranate extract with (LC₅₀ = 2852 µg/ml). The results indicated that obvious increase in polyphenols content in silver nanoparticles enhance their larvicidal effect and increasing mortality of 1^st larval of S. littoralis Egyptian leafworms causing additive effect and synergism. We recommend recycling phenolic enriched agricultural wastes in producing green silver nanoprticles to control cotton leafworm that causes economic loses to crops.

Green synthesis and characterization of titanium dioxide nanoparticles using leaf extract of Pouteria campechiana and larvicidal and pupicidal activity on Aedes aegypti

The frequent application of synthetic insecticides creates resistance among insects, including mosquitoes, and causes environmental pollution and health issues. The current work aim at assessing the possibilities to produce and characterize the titanium dioxide (TiO₂) nanoparticles (TiO₂ NPs) mediated through the aqueous leaf extract of Pouteria campechiana, and their larvicidal and pupicidal activities against Aedes aegypti. The attained results showed that the aqueous leaf extract of P. campechiana had the efficiency to fabricate TiO₂ NPs from TiO₂. Under the UV-vis spectrum analysis, a sharp peak was recorded at 320 nm, which indicated the production of TiO₂ NPs by the plant extract. The SEM analysis revealed that the synthesized TiO₂ NPs were spherical, and 5 dissimilar diffractions were detected in the XRD spectrum analysis related to the TiO₂ NPs. In FTIR analysis, a prominent peak was found at 1052.41 cm^-1, corresponding to alcohol, and confirmed metal reduction. In the EDX analysis, there was a signal of around 58.44%, confirming the decrease in Ti from TiO₂ NPs, and the remaining percentages were Ca, Al, and Mg. About 900 μg mL^-1 of TiO₂ NPs had excellent lethal activity against various larvae and pupa stages of Ae. aegypti. The attained results showed that the P. campechiana aqueous leaf extract could reduce TiO₂ into TiO₂ NPs and could be considered a mosquito control agent. Furthermore, this is the initial report about the aqueous leaf extract of P. campechiana effectively synthesizing the TiO₂ NPs with anti-mosquito activity.

Synthesis and characterization of TiO2 NPs by aqueous leaf extract of Coleus aromaticus and assess their antibacterial, larvicidal, and anticancer potential

The frequent applications of synthetic chemical insecticides and drugs create resistance among insects and microbes, creating a new threat to human and environmental welfare. This investigation focused on evaluating the possibilities of fabricating and characterizing the titanium dioxide nanoparticles (TiO₂ NPs) from titanium dioxide (TiO₂) through the aqueous leaf extract of Coleus aromaticus. Their biological applications were studied against the larvae of Aedes aegypti human pathogenic bacteria, and cancer cell line. The results revealed that the aqueous leaf extract had the metal reducing proficiency to produce nanoparticles from TiO₂. The synthesized TiO₂ NPs were initially confirmed by visible color changes and Ultraviolet-Visible Spectrophotometer analysis that showed a predominant peak at 332 nm. Furthermore, the nanocrystals, structural alignment, functional groups and elemental compositions were studied by following standard operating protocol in XRD (X-ray Powder Diffraction), FTIR (Fourier Transform Infrared Spectroscopy), TEM (Transmission Electron Microscopy), and EDX (Energy-Dispersive X-ray Spectroscopy) techniques, respectively. The results attained from these techniques confirmed that the plant mediated and fabricated particles were in the nanoscale range (12-33 nm) with a hexagonal shape. The synthesized TiO₂ NPs had an outstanding (1000 μg mL^-1) larvicidal activity against the four stages of instars larvae of Ae. aegypti at 1000 μg mL^-1. It also had an excellent antibacterial potential against E. faecalis (33 mm), followed by S. boydii (30 mm) at 30 mg L^-1 concentration. The green fabricated TiO₂ NPs had a fabulous (92.37%) cytotoxic activity on the HeLa cell line at 100 μg mL^-1 dosage within one day of exposure. The entire results concluded that the C. aromaticus mediated TiO₂ NPs have excellent biological applications and thus, could be considered for the welfare of human beings.

Artificial modification of the chemical composition of orange oil (Citrus sinensis L.) and its effect on larvicidal activity

The use of synthetic pesticide carries along several disadvantages talking about the preservation of the natural homeostasis of the planet, causing the searching of biopesticide, which one presents advantages as well as biodegradability in minimum possible time, the low toxicity in comparison to synthetic pesticides and their variety of structure, which allows slowing down the appearance of resistance. The aim of this work was to evaluate the effect on the larvicidal action when artificially varying the chemical composition of orange oil (Citrus sinensis L.). As results, we found that the analysis of gas chromatography coupled to mass spectrometry showed the presence of terpenoid and sesquiterpenoid compounds in the different samples. The use of electric pulses on samples modified their chemical composition, so that the percentage of limonene went from 72% in the sample that was not subjected to electric treatment to lower percentages, even in sample three the percentage of limonene was <50%. Only three compounds (limonene, linalool and caryophyllene) were found to be common in all samples. Subsequently, the larvicidal action on Drosophila melanogaster larvae was evaluated. Six concentrations of each oil sample were tested (0, 100, 500, 1000, 5000 and 10000 ppm). We found that there was no linear relationship between concentration and lethality. Additionally, in the sample without electrical treatment most of the concentrations tested had lethality higher than 50%, while in sample 7 the results of the lethality were lower than 30%, so that biological tests showed that in samples where the concentration of limonene was lower, the lethality in the larvae decreased.

Piper capitarianum essential oil: a promising insecticidal agent for the management of Aedes aegypti and Aedes albopictus

Mosquitoes are responsible for serious public health problems worldwide, and as such, Aedes aegypti and Aedes albopictus are important vectors in the transmission of dengue, chikungunya, and Zika in Brazil and other countries of the world. Due to growing resistance to chemical insecticides among populations of vectors, environmentally friendly strategies for vector management are receiving ever more attention. Essential oils (EOs) extracted from plants have activities against insects with multiple mechanisms of action. These mechanisms hinder the development of resistance, and have the advantages of being less toxicity and biodegradable. Thus, the present study aimed to evaluate the chemical composition of the EOs obtained from Piper capitarianum Yunck, as well as evaluating their insecticidal potential against Aedes aegypti and A. albopictus, and their toxicity in relation to Artemia salina. The yields of the EOs extracted from the leaves, stems, and inflorescences of P. capitarianum were 1.2%, 0.9%, and 0.6%, respectively, and their main constituents were trans-caryophyllene (20.0%), α-humulene (10.2%), β-myrcene (10.5%), α-selinene (7.2%), and linalool (6.0%). The EO from the inflorescences was the most active against A. aegypti and A. albopictus, and exhibited the respective larvicidal (LC₅₀ = 87.6 μg/mL and 76.1 μg/mL) and adulticide activities (LC₅₀ = 126.2 μg/mL and 124.5 μg/mL). This EO was also the most active in the inhibition of AChE, since it presented an IC₅₀ value of 14.2 μg/mL. Its larvicidal effect was observed under optical and scanning electron microscopy. Additionally, non-toxic effects against A. salina were observed. Docking modeling of trans-caryophyllene and α-humulene on sterol carrier protein-2 (SCP-2) suggests that both molecules have affinity with the active site of the enzyme, which indicates a possible mechanism of action. Therefore, the essential oil of P. capitarianum may be used in the development of new insecticide targets for the control of A. aegypti and A. albopictus in the Amazonian environment.

Evaluation of Larvicidal Efficacy of Ricinus communis (Castor) Plant Extract and Synthesized Green Silver Nanoparticles against Aedes albopictus

Background

Aedes mosquitoes are the most important group of vectors having ability of transmitting pathogens including arboviruses that can cause serious diseases like Chikungunya fever, Dengue fever and Zika virus in human. Biosynthesis and the use of green silver nanoparticles (AgNPs) is an important step in the search of reliable and ecofriendly control of these vectors.

Methods

In this study an aqueous leaves extract of Ricinus communis (castor) and silver nanoparticles (AgNPs) synthesized from this extract were evaluated as larvicidal agent for 2^nd and 3^rd instar larvae of the Aedes albopictus. Different concentrations (50, 100, 150, 200 and 250ppm) of plant extract and synthesized nanoparticles were prepared and applied on second and third instar larvae. The percent mortality was noted after 6, 12, 18, 24, 30, 36, 42 and 48H of exposure and subjected to probit analysis to calculate LC₅₀ and LC₉₀.

Results

Synthesized Ag⁺ nanoparticles were characterized by UV-Vis spectroscopy, Fourier transform infrared spectroscopy (FT-IR), and energy-dispersive X-ray spectroscopy (XRD). The nanoparticles were more toxic against larvae of Ae. albopictus with LC₅₀ value (49.43ppm) and LC₉₀ value (93.65ppm) for 2^nd instar larvae and LC₅₀ (84.98ppm) and LC₉₀ (163.89ppm) for 3^rd instar larvae as compared to the plant extract (149.58ppm, 268.93ppm) and (155.58ppm, 279.93ppm) for 2^nd and 3^rd instar larvae of Ae. albopictus respectively after 48H.

Conclusion

Our results suggest the extract of R. communis and synthesized nanoparticles as excellent replacement of chemical pesticides to control the vector mosquitoes.

Serratia marcescens secretes proteases and chitinases with larvicidal activity against Anopheles dirus

Vector control, the most efficient tool to reduce mosquito-borne disease transmission, has been compromised by the rise of insecticide resistance. Recent studies suggest the potential of mosquito-associated microbiota as a source for new biocontrol agents or new insecticidal chemotypes. In this study, we identified a strain of Serratia marcescens that has larvicidal activity against Anopheles dirus, an important malaria vector in Southeast Asia. This bacterium secretes heat-labile larvicidal macromolecules when cultured under static condition at 25°C but not 37°C. Two major protein bands of approximately 55 kDa and 110 kDa were present in spent medium cultured at 25°C but not at 37°C. The Liquid Chromatography-Mass Spectrometry (LC-MS) analyses of these two protein bands identified several proteases and chitinases that were previously reported for insecticidal properties against agricultural insect pests. The treatment with protease and chitinase inhibitors led to a reduction in larvicidal activity, confirming that these two groups of enzymes are responsible for the macromolecule's toxicity. Taken together, our results suggest a potential use of these enzymes in the development of larvicidal agents against Anopheles mosquitoes.

Evaluation of larvicidal efficacy of Ricinus communis (Castor) and synthesized green silver nanoparticles against Aedes aegypti L

Aedes mosquitoes are the most important group of vectors that transmit pathogens, including arboviruses, and cause human diseases such as dengue fever, yellow fever, Zika virus, and Chikungunya. Biosynthesis and the use of green silver nanoparticles (AgNPs) is a vital step to identify reliable and eco-friendly controls for these vectors. In this study, Aedes (Ae.) aegypti larvae (2nd and 3rd instar) were exposed to leaf extracts of Ricinus communis (Castor) and AgNPs synthesized from the extract to evaluate their larvicidal potential. Synthesized AgNPs were characterized by UV-Vis spectroscopy, Fourier transform infrared spectroscopy (FTIR), and energy-dispersive X-ray spectroscopy (XRD). Ae. aegypti larvae were treated with different concentrations (50-250 ppm) of the leaf extract and synthesized AgNPs. There were five replicates per treatment, in addition to a positive (temephos) and negative control (dechlorinated water). Mortality was recorded after 12, 24, 36, and 48 h and the data were subjected to Probit analysis. The nanoparticles were more toxic (LC50 = 46.22 ppm and LC90 = 85.30 ppm) than the plant extract (106.24 and 175.73 ppm, respectively). The leaf extracts of Ricinus communis were subjected to HPLC analysis to identify their chemical constituents. This study suggests that plant extracts and synthesized nanoparticles are excellent alternatives to hazardous chemical pesticides used to control vector mosquitoes. This is a potentially useful technique that can reduce aquatic toxicity from insecticide use.

Dye degradation, antimicrobial and larvicidal activity of silver nanoparticles biosynthesized from Cleistanthus collinus

The present study aimed in green synthesis and characterization of silver nanoparticles (AgNPs) using the leaves of Cleistanthus collinus. The NPs showed various absorption peaks between 3402 cm-1 and 1063 cm-1. FTIR spectrum revealed the presence of OH group, alkene, aromatic hydrocarbon, aliphatic fluro compound and aliphatic chloro compounds. Scanning electron microscopic analysis revealed the particle size ranged from 30 to 50 nm. The biosynthesized NPs have potent activity against Shigella dysentriae, Staphylococcus aureus and Bacillus subtilis and the zone of inhibition was 21 ± 1, 20 ± 2, 16 ± 2 mm, respectively. Toxicity of the synthesized NPs was tested on green gram (Vigna radiata) seed at various concentrations (20-100%) and germination was induced by NPs treated seeds. Shoot length and root length was higher in NPs treated plant than control plant (p < 0.01). Elevated level of catalase (CAT) and superoxide dismutase (SOD) and about 13% CAT and 7% SOD activity registered than control. Superoxide dismutase activity of root and shoot varied based on the dosage of AgNPs (p < 0.01). Also, the NPs (1%) showed significant larvicidal activity on Aedes aegypti and 100% mortality was achieved after 24 h treatment. The green synthesized NPs reduced methylene blue and 4-nitrophenol significantly (p < 0.01). The colouration of methylene blue and 4-nitrophenol were considerably reduced after 60 min showed the potential of dye degrading ability.

Multifunctional properties of spherical silver nanoparticles fabricated by different microbial taxa

This study addresses the impacts of metabolites from different microbial taxa on the fabrication and multifunctional biological properties of spherical silver nanoparticles (Ag-NPs). Three microbial taxa, a bacterial (Bacillus cereus A1-5), actinomycetes (Streptomyces noursei H1-1), and fungal (Rhizopus stolonifer A6-2) strains were used for Ag-NPs biosynthesis, whereas Streptomyces noursei is demonstrated for the first time. These isolates were identified using either 16S rRNA or ITS gene sequencing. Characterization of Ag-NPs was done using color change analysis, Uv-Vis spectroscopy, FT-IR spectroscopy, XRD, TEM, SEM-EDX, DLS, and Zeta potential analysis. All biosynthesized NPs exhibited spherical shape with different sizes ranged from 6‒50 nm, 6-30 nm and 6-40 nm for NPs obtained by A1-5, H1-1 and A6-2, respectively. The crystalline center cubic face of Ag-NPs was confirmed using XRD at 2θ values 38.08o, 44.27o, 64.41o and 77.36o. FT-IR analysis revealed varied intense absorption peaks for biomolecules required for NPs synthesize by each microbial strain. The stability of spherical Ag-NPs was confirmed due to highly DLS negative surface charge of ‒17.5mV, ‒18.9mV, and ‒15.6mV for NPs synthesized by strains A1-5, H1-1, and A6-2, respectively. Ag-NPs exhibited a broadspectrum of antibacterial activity against Gram-positive and Gram-negative bacteria with varied effectiveness. They also exhibited a cytotoxic effect against cancer cell line (caco-2) in a dose-dependent pattern with IC50 of 8.9 ± 0.5, 5.6 ± 3.0, 11.2 ± 0.5 μg/ml for NPs synthesized by strains A1-5, H1-1, and A6-2, respectively. Moreover, these spherical Ag-NPs showed larvicidal activity against the 3rd instar larvae of the dengue vector Aedes aegypti.

Larvicidal Activity of Ketapang Leaf Fraction (Terminalia catappa L) on Aedes aegypti Instar III

BACKGROUND:

Mosquito control is essential in preventing mosquito-borne diseases. Natural substances originated from plants possessed the great potential of insecticidal properties, the resistance occurs at a slower rate compared to the synthetics, with less toxicity to other living creatures.

AIM:

This study aimed to identify the fraction of ketapang leaf (Terminalia catappa L) with larvicidal activity on Aedes aegypti instar III larvae, the concentration of ketapang active leaf fraction comparable to temephos, and Lethal Concentration 50 (LC50).

METHODS:

This study was experimental in vitro. The experiment was performed with five different concentrations of ketapang leaf water-ethanol fraction, i.e. 1200 ppm, 1400 ppm, 1600 ppm, 1800 ppm, 2000 ppm. Observation of morphological damage of mosquito larvae was conducted with the microscope and ImageJ application. Data analysis was performed using One Way ANOVA. LC50 was determined with probit analysis.

RESULTS:

Phytochemical screening revealed a water-ethanol fraction of ketapang leaf contained tannin, saponin, and flavonoid compounds. The water-ethanol fraction with 1800 ppm concentration possessed significant larvicidal effect comparable to temephos. Probit test revealed an LC50 value of 1563.082 μg/ml.

CONCLUSION:

Water-ethanol fraction of ketapang leaf possessed high biolarvicidal activity against Ae. aegypti larvae instar III comparable to temephos.

Evaluation of larvicidal activity of esters of 4-mercapto-2-butenoic acid against Aedes albopictus (Diptera: Culicidae)

Aedes albopictus (Skuse) (Diptera: Culicidae), an aggressive and annoying vector of several arbovirus including Chikungunya and Zika, is a serious health problem worldwide. Control of this mosquito is difficult because of high adaptability, egg resistance to dehydration and ability to exploit many man-made microhabitats. The most effective strategy appears the control of larval population. Based on previous data showing a larvicidal effect of plant extracts containing sulfhydryl and isothiocyanate compounds, we evaluated by bioassays the toxicity of three synthetic esters of 4-mercapto-2-butenoic acid on larvae of A. albopictus in comparison to cypermethrin. Among the compounds tested, the most effective was n-octyl 4-mercapto-2-butenoate, about 5 times more effective than ethyl 4-mercaptobut-2-enoate and about 20 times more effective than menthyl 4-mercaptobut-2-enoate. We advance the hypothesis that the larvicidal properties of n-octyl 4-mercapto-2-butenoate are due to its hydrophobic alkyl chain, longer than that of the other two compounds. This chain confers to the molecule the ability to spread on water surface and interfere with larval respiration. The larvicidal activity of n-octyl 4-mercapto-2-butenoate against A. albopictus appears interesting and may be developed after toxicological evaluation on vertebrates and humans, and environmental toxicity tests in compliance with WHO and ECDC rules.

Enhanced mosquitocidal efficacy of colloidal dispersion of pyrethroid nanometric emulsion with benignity towards non-target species

The rising threat of vector-borne diseases and environmental pollution has instigated the investigation of nanotechnology-based applications. The current study deals with a nanotechnological application involving the usage of nanometric pesticides such as permethrin nanoemulsion. The mean droplet diameter and zeta potential of the prepared permethrin nanoemulsion were found to be 12.4 ± 1.13 nm and -20.4 ± 0.56 mV, respectively. The temporal stability of permethrin nanoemulsion was found to be 4 days when checked in the external environment. The permethrin nanoemulsion exhibited LC₅₀ values of 0.038 and 0.047 mgL-1 and 0.049 and 0.063 mgL^-1 against larval and pupal stages of Culex tritaeniorhynchus and Aedes aegypti, respectively. The results obtained from the larvicidal and pupicidal assay were corroborated with the histopathological and biochemical profiles of hosts upon treatment with nanometric pesticide. Further, the biosafety studies of the nanopesticide were carried out against different non-target species like freshwater algae (Closterium), Cicer arietinum (Chickpea) and Danio rerio (Zebrafish), and the mosquitocidal concentration of nanopesticide was found to be non-toxic. The following study, therefore, describes the mosquitocidal efficacy of nanometric pesticide formulated in a greener approach, which can become a substitute for conventional pesticide application in an eco-benign manner.

Bioengineering of Piper longum L. extract mediated silver nanoparticles and their potential biomedical applications

The present investigation highlights the strong antioxidant, anticancer and larvicidal potential of green synthesized silver nanoparticles (AgNPs) using aqueous leaf extract of Piper longum L. for their diverse therapeutic applications. The optimum conditions for the synthesis of AgNPs were recorded as 1 mM AgNO₃, 60 ± 2 °C at pH 6 for 120 min. Synthesized AgNPs proved to be highly stable and monodispersed as characterized through various techniques. UV-Vis spectrum of biosynthesized AgNPs showed a maximum absorption peak at 420 nm. Field emission-Scanning electron microscopy (FE-SEM) and High resolution-Transmission electron microscopy (HR-TEM) micrographs showed the spherical shape of AgNPs with mean diameter size of 28.8 nm. Existence of crystallographic AgNPs was proved by X-ray diffraction (XRD) pattern analysis. Presence of phenolics, terpenoids and flavonoids compounds which act as bioreducing agents were confirmed by Fourier-transform infrared spectroscopy (FTIR) analysis. Furthermore, the AgNPs and leaf extracts prepared individually in different solvents such as methanol, ethyl acetate, chloroform, hexane and aqueous were assessed for their bio-efficacies. AgNPs showed the enhanced antioxidant (IC₅₀ 67.56 μg) and radical-scavenging activities (IC₅₀ 196.8 μg) as compared to the crude leaf extracts. Anticancer activity revealed the strong and dose-dependent cytotoxic effect of AgNPs against the HeLa cells showing maximum IC₅₀ value being 5.27 μg/mL after 24 h and was also found to be non-toxic to normal cells (HEK). The AgNPs induced the fragmentation of DNA in the cells, indicating the occurrence of apoptosis and necrosis. Subsequently, an efficient larvae mortality was also recorded against Anopheles stephensi having LC₅₀ and LC₉₀ values being 8.969 and 16.102 ppm, followed by Aedes aegypti (LC₅₀;14.791 and LC₉₀;28.526 ppm) and Culex quinquefasciatus (LC₅₀;18.662 and LC₉₀;40.903 ppm) after 72 h of exposure. Besides, they showed no toxicity against Mesocyclops thermocyclopoides (non-target organism). This is the first report showing strong anti-tumorous and larvicidal activity of AgNPs synthesized using P. longum leaf extract against cervical cancer cell line and mosquito vectors causing dengue, malaria and filariasis. Based on our findings, we suggest that AgNPs derived using P. longum leaf extract possessed excellent anti-cancerous and mosquito larvicidal potential and therefore, can be bioprospected further for the management of these hazardous health diseases. This study has given a new insight for the novel drug designing after conducting experiments on the in vivo models.

Honeysuckle essential oil as a potential source of ecofriendly larvicides for mosquito control

BACKGROUND

Some plant essential oils have insecticidal properties against mosquitoes and can be harnessed as ecofriendly tools for mosquito control. We conducted bioassays to determine the toxicity of Italian honeysuckle (Lonicera caprifolium) essential oil and its fractions against larvae of the yellow fever mosquito, Aedes aegypti.

RESULTS

Sixteen constituents were identified in honeysuckle essential oil compared to 15, 15, 15, and 11 constituents in fractions A, B, C, and E, respectively. The chemical constituents for fraction D were not determined due to lack of enough fraction sample. The two major constituents identified were patchouli alcohol (29.3%) and 6-acetyl-1,1,2,4,4,7-hexamethyltetralin (20.6%) in whole essential oil, alpha-bulnesene (27.6%) and 6-acetyl-1,1,2,4,4,7-hexamethyltetralin (23.2%) in fraction A, unknown chemical (47.3%) and diethyl phthalate (19.5%) in fraction B, unknown chemical (38.3%) and diethyl phthalate (23.2%) in fraction C, and patchouli alcohol (58.7%) and diethyl phthalate (20.5%) in fraction E. The LC₅₀ for whole essential oil was 34.4 ppm and significantly higher than 20.6, 19.7, 18.6, and 17.7 ppm for fractions B, C, D, and E, respectively. In contrast, fraction A was inactive. At 50 ppm, all individual constituents tested were less toxic than the whole essential oil with exception of patchouli alcohol, which caused 100% mortality.

CONCLUSION

These findings suggest that patchouli alcohol is one of the chemical constituents responsible for bioactivity of honeysuckle essential oil and some of its fractions. The findings also demonstrate that honey suckle essential oil and its fractions can be exploited as a source of ecofriendly larvicides for mosquito control. Published 2019. This article is a U.S. Government work and is in the public domain in the USA.

Tunicates as a biocontrol tool for larvicides acute toxicity of Zika virus vector Aedes aegypti

In this present study, we conducted untargeted metabolic profiling using gas chromatography-mass spectrometry (GC-MS) analysis of ascidian Didemnum bistratum to assess the chemical constituents by searching in NIST library with promising biological properties against anti-bacterial and Zika virus vector mosquitocidal properties. Metabolites, steroids and fatty acids are abundant in crude compounds of ascidian D. bistratum and showed potential zone growth inhibition against bacterial strains Kluyvera ascorbate (10 mm). The active crude compounds of D. bistratum exhibited prominent larvicidal activity against the Zika vector mosquitoes of Aedes aegypti (LC50 values of 0.44 mg/ml) and Cluex quinquefasciatus (LC50 values of 2.23 mg/ml). The findings of this study provide a first evidence of the biological properties exhibited by D. bistratum extracts, thus increasing the knowledge about the Zika virus vector mosquitocidal properties of ascidian. Overall, ascidian D. bistratum is promising and biocontrol or eco-friendly tool against A. aegypti and C. quinquefasciatus with prospective toxicity against non-target organisms.

Biocontrol and non-target effect of fractions and compound isolated from Streptomyces rimosus on the immature stages of filarial vector Culex quinquefasciatus Say (Diptera: Culicidae) and the compound interaction with Acetylcholinesterase (AChE1)

The present study was aimed to check the mosquitocidal activity of intracellular methanol extract fractions and the compound di (2-ethylhexyl) phthalate isolated from Streptomyces rimosus. The isolated compound was also analyzed for its interaction with Acetylcholinesterase (AChE1). The larvae and eggs of Culex quinquefasciatus were exposed to four different concentrations such as 2.5, 5.0, 7.5 and 10 ppm for fractions and 0.5, 1.0, 1.5 and 2.0 ppm for compound. After 24 and 120 h post treatment, the larval mortality and ovicidal activity were recorded. Fractions collected from the intracellular methanol extract were tested for larvicidal activity; among them Fraction 4 was found to be the active fraction. Fraction 4 showed 74% larvicidal activity with LC₅₀ and LC₉₀ values of 6.9 and 17.2 ppm, respectively, in 24 h against the larvae of Cx. quinquefasciatus. Fraction 4 showed 95% ovicidal activity at 10 ppm concentration after 120 h post treatment. The eluted compound di(2-ethylhexyl) phthalate was highly toxic and exhibited promising activity against the eggs of Cx. quinquefasciatus. The compound presented 94% ovicidal activity at 2.0 ppm concentration after 120 h post treatment. The larvae of Cx. quinquefasciatus were exposed to di(2-ethylhexyl) phthalate which showed good activity in a concentration-dependent manner. The compound showed 76% larvicidal activity against the larvae of Cx. quinquefasciatus with LC₅₀ and LC₉₀ values of 1.22 and 3.28 ppm, respectively, at 2 ppm concentration in 24 h. Fraction 4 and the compound were subjected to toxicity study against non-target organism and were found to be nontoxic. The present studies revealed that the treated larvae showed serious damage in the midgut cells. Growth disruption and larval deformities were observed in compound-treated larvae. The compound was highly active and inhibited AChE in a concentration-dependent manner. Computational analysis of the compound had strong interaction with AChE1 of Cx. quinquefasciatus. These results clearly showed that Fraction 4 and the compound isolated from S. rimosus can be used to control the life stages of Cx. quinquefasciatus; it will be a good alternative to synthetic insecticides.

Target and non-target toxicity of fern extracts against mosquito vectors and beneficial aquatic organisms

Dengue and malaria are significant mosquito-borne diseases that are rapidly spread worldwide, mainly in temperate countries. Pteridophytes were identified to be a significant source of novel mosquitocidal agents. The present research was to explore the eco-friendly larvicides from methanol extracts of ferns, viz., Actiniopteris radiata, Adiantum caudatum, Cheilanthes swartzii, Hemionitis arifolia and Lycopodium clavatum. The larvicidal potential of the extracts screened using larvae of dengue vector Aedes aegypti (III and IV instar) and malarial vector Anopheles stephensi (III and IV instar), showed 10-100% mortality rates. Biosafety assessment was made on embryos of Danio rerio and Artemia nauplii. The phyto-constituents of the methanol extract of A. radiata leaves were identified through gas chromatography-mass spectrometry (GC-MS). Methanolic leaf extracts of A. radiata, A. caudatum and C. swartzii exhibited larvicidal activity against III and IV instar larvae of Ae. aegypti (LC₅₀: 37.47, 74.51 and 152.38 and 67.58, 95.89 and 271.46 ppm) and An. stephensi (LC₅₀: 70.35, 112.12 and 301.05 and 113.83, 175.30 and 315.19 ppm), respectively. The GC-MS of the methanol extract of A. radiata leaves revealed the presence of 7 phyto-components among which, Carbamic acid, phenyl-, (2-Nitrophenyl) methyl ester (1), Benzoic acid, 3- methylbenzoate (2) and 4-(benzylimino)- 1,4-dihydro-1-(p-toluoylmethyl) pyridine (3) were dominant. Biosafety assessment of methanol extract of A. radiata leaves on embryos of Danio rerio (Zebra fish) and Artemia nauplii (micro crustacean) revealed that there were no destructive or teratogenic effects. To conclude, the larvicidal activity and insignificant toxicity to non-target aquatic organisms of A. radiata leaves makes it a potential and environment safe biocontrol agent against dengue and malarial vectors.

Cyclic lipopeptide biosurfactant from Bacillus tequilensis exhibits multifarious activity

Bacillus tequilensis strain CH had been previously shown to produce a biosurfactant. In this study, chemical structure of the purified biosurfactant was determined by using high performance liquid chromatography and liquid chromatography-mass spectroscopy as a 10 amino acid cyclic lipopeptide (CL). The cyclic lipopeptide was found to be active against Anopheles culicifacies larvae with a LC₅₀ of 110 µg/ml in 2 days. 1 ppm cadmium (Cd) which had a profound mutagenic effect on the cell division of onion (Allium cepa) root tip cell resulting in abnormal metaphase, abnormal anaphase and nuclei elongation was partially reversed in the presence of 0.1 mg/ml of CL (52% cells dividing normally and 8% with abnormal division) and was comparable to control experiment where no Cd was present. Thus, the CL described in this report may have applications in eliminating larvae from water repository systems and in reversing the effects of cadmium pollution.

Toxicity studies of nanofabricated palladium against filariasis and malaria vectors

The present study was carried out to establish the biofabrication of palladium nanoparticles (PdNPs) using the plant leaf extract of Tinospora cordifolia Miers and its toxicity studies on the larvae of filariasis vector, Culex quinquefasciatus Say and malaria vector, Anopheles subpictus Grassi. The biofabricated PdNPs were characterized by using UV-visible spectrum, FTIR, XRD, FESEM, EDX and HRTEM. HRTEM confirmed the PdNPs were slightly agglomerated and spherical in shape and the average size was 16 nm. Gas chromatography and mass spectrometry analysis result revealed that the major constituent present in the T. cordifolia leaf extract is 2,4-di-tert-butylphenol (31.79%) whereas the minor compounds are 1-hexadecanol (7.97%), 1-octadecanol (7.70%), 1-eicosanol (6.85%), behenic alcohol (5.36%), 1-tetradecene (6.22%), cyclotetradecane (6.23%), 1-hexadecene (7.97%), 1-octadecene (7.70%), 1-eicosene (6.85%), and 1-docosene (5.36%). T. cordifolia leaf extract exhibited the larvicidal activity against the fourth instar larvae of C. quinquefasciatus and A. subpictus with the values of LC₅₀ = 59.857 and 54.536 mg/L; LC₉₀ = 113.445 and 108.940 mg/L, respectively. The highest toxicity was observed in the biofabricated PdNPs against the fourth instar larvae of C. quinquefasciatus and A. subpictus with the values of LC₅₀ = 6.090 and 6.454 mg/L; LC₉₀ = 13.689 and 13.849 mg/L, respectively. Concerning non-target effects, Poecilia reticulata were exposed to PdNPs for 24 h and did not exhibit any noticeable toxicity. Overall, our findings strongly suggest that PdNPs is a perfect ecological and inexpensive approach for the control of filariasis and malaria vectors.

Environmentally benign nanometric neem-laced urea emulsion for controlling mosquito population in environment

The increasing risk of vector-borne diseases and the environmental pollution in the day-to-day life due to the usage of the conventional pesticides makes the role of nanotechnology to come into the action. The current study deals with one of the applications of nanotechnology through the formulation of neem urea nanoemulsion (NUNE). NUNE was formulated using neem oil, Tween 20, and urea using the microfluidization method. Prior to the development of nanoemulsion, the ratio of oil/surfactant/urea was optimized using the response surface modeling method. The mean droplet size of the nanoemulsion was found to be 19.3 ± 1.34 nm. The nanoemulsion was found to be stable for the period of 4 days in the field conditions which aids to its mosquitocidal activity. The nanoemulsion exhibited a potent ovicidal and larvicidal activity against A. aegypti and C. tritaeniorhynchus vectors. This result was corroborated with the histopathological analysis of the NUNE-treated larvae. Further, the effect of NUNE on the biochemical profile of the target host was assessed and was found to be efficacious compared to the bulk counterpart. The nanoemulsion was then checked for its biosafety towards the non-target species like plant beneficial bacterium (E. ludwigii), and phytotoxicity was assessed towards the paddy plant (O. sativa). Nanometric emulsion at the concentration used for the mosquitocidal application was found to be potentially safe towards the environment. Therefore, the nanometric neem-laced urea emulsion tends to be an efficient mosquito control agent with an environmentally benign property.

Toxic effects of Solanum xanthocarpum Sch &Wendle against Helicoverpa armigera (Hub.), Culex quinquefasciatus (Say.) and Eisenia fetida (Savigny, 1826)

Many commercially available agro and household chemicals are used as pesticides, repellents, and growth inhibitors against insect pests. The repeated uses of these chemicals against insect pests have caused the development of resistance in them; they also cause ill effects on nontarget organisms. The present study was aimed to evaluate the antifeedant, larvicidal, pupicidal, and biochemical effects of the solvent extracts of Solanum xanthocarpum against third instar larvae of Helicoverpa armigera. Hexane, chloroform and ethyl acetate extracts were subjected to phytochemical analysis. The results revealed the presence of terpenoids, flavonoid, and quinone. Maximum antifeedant activity of 72.30% was recorded in chloroform extract followed by hexane (69.02%) and ethyl acetate (57.40%) extracts against H. armigera. Chloroform extracts of S. xanthocarpum showed more than 60% larvicidal and pupicidal activity against H. armigera. The effective chloroform extract was fractionated with increasing polarity of solvent system (hexane, chloroform, and ethyl acetate extracts). Based on the TLC profile, nine major fractions were isolated. The fourth fraction showed higher antifeedant, larvicidal, and pupicidal activity against H. armigera. The effective fraction reduced the hemolymph and gut protein concentration in a concentration-dependent manner (r ² 0.99). The effective fraction 4 showed 100% larvicidal activity at 500 ppm concentration with LC₅₀ value of 227.95 ppm. The fourth fraction did not show any toxic symptom or mortality of earthworm. Based on these results, this effective fraction could be used in the development of a pesticide formulation to control insect.

Assessment of Achyranthes aspera induced toxicity and molecular analysis of RAPD-PCR profiles of larval genomic DNA of Aedes aegypti L. (Diptera: Culicidae)

Current studies investigated the anti-mosquito potential of Achyranthes aspera against the dengue vector, Aedes aegypti. The stems and leaves of A. aspera were extracted in hexane and evaluated for their toxicity against early fourth instars of A. aegypti. The larvicidal efficacy of the extract was validated as per WHO protocol. The mortality counts were made after 24 h and LC values were calculated at different levels. The adverse impact of extracts was also explored on the larval genomic DNA. The larvae were exposed to extracts at LC₅₀ levels and the alterations in g-DNA was evaluated through RAPD-PCR technique using three random primers; MA-09, MA-12 and MA-26. Our investigations ascertained the larvicidal efficacy of both the leaf and stem extracts of A. aspera resulting in respective LC₅₀ values of 0.068 and 0.082 mg/mL. The extracts also caused variable genotoxic effects with significant changes in the RAPD profiles. The results showed appreciable modifications in larval g-DNA with loss of certain bands and gain of unique bands with 82.35% DNA polymorphism. These alterations suggest the probable DNA damage and mutations in the larval g-DNA caused by certain phytocomponents which could be the possible reason of larval mortality. Our studies evidenced the anti-mosquito potential of A. aspera extracts against A. aegypti causing appreciable larval mortality and significant changes in g-DNA. The A. aspera extracts are suggested as efficient and eco-friendly control agent against A. aegypti, yet further investigations are needed to identify the bioactive constituent and ascertain its effectiveness in the field conditions.

Larvicidal effect of Endod (Phytolacca dodecandra) seed products against Anopheles arabiensis (Diptera: Culicidae) in Ethiopia

OBJECTIVE

The purpose of the present study was to determine the larvicidal effect of 'Endod' (Phytolacca dodecandra) seed products on Anopheles arabiensis, in Ethiopia.

RESULTS

Experimental study was conducted using a total of 2400 third instars larvae of A. arabiensis. The seed products P. dodecandra showed larvicidal activity against 3rd-stage larvae of both the laboratory and field population of A. arabiensis. The LC₉₉ values for P. dodecandra's seed powder and its extract form against the laboratory reared larvae were 121.07, and 616.46 mg/l, respectively. The LC₅₀ and LC₉₅ values were also determined.