Larvicidal activity of Hypoestes forskaolii (Vahl) R. Br root extracts against Anopheles gambiae Giless.s, Aedes aegypti L, and Culex quinquefasciatus Say

Assessment of larvicidal and genotoxic potentials of extracts of Hyptis suaveolens against Culex quinquefasciatus based on enzyme profile and RAPD-PCR assay

Vector control strategies have focused on the development of effective and ecofriendly alternatives. In the present study, investigation of larvicidal and genotoxic effects of leaves of Hyptis suaveolens from four different extraction solvents (aqueous, hexane, methanol and acetone) on fourth instar larvae of Culex quinquefasciatus was carried out. Extraction was done using soxhlet apparatus and the characteristics functional group of active constituents were identified using Fourier Transform Infrared spectrophotometer. Larvicidal activities were screened using three different concentrations (50, 150 and 250 mg/mL) following WHO standard protocol and mortality was recorded after 24, 48 and 72 hr. Hexane extract showed the highest mortality (27.92, 38.75, 90.42 %; LC₅₀: 272.5, 191.3, 114.8 mg/mL), followed by aqueous extract (20.83, 34.58, 59.58 %; LC₅₀: 496.6, 392.9, 208.1 mg/mL) and acetone extract (20.83, 32.08, 59.58 %; LC₅₀: 1111.2, 393.6, 266.1 mg/mL) and methanol extract (17.92, 29.17, 52.92 %; LC₅₀: 466.0, 400.1, 272.3 mg/mL). Enzyme profile such as superoxide dismutase (SOD), glutathione-S-transferase (GST), catalase (CAT), glutathione (GSH) and alkaline phosphatase (ALP) were significantly altered in the larvae exposed to the four extracts. Phytochemical screening of all solvents extract revealed the presence of saponins, flavonoids, terpenoids and alkaloids as common constituents. Random Amplified Polymorphic DNA-Polymerase Chain Reaction (RAPD-PCR) profile implied hexane and aqueous extracts altered the DNA of larvae. Furthermore, FTIR Spectroscopic analysis revealed phenols, alcohols, aliphatic primary amines and saponins as the major groups in the extracts. Conclusively, this study established the lethal potential of extracts of H. suaveolens as alternative plant-based and eco-friendly larvicide against Cx. quinquefasciatus.

Target and non-target effects of Foeniculum vulgare and Matricaria chamomilla combined extract on Culex pipiens mosquitoes

The present study focused on extracting green larvicides from extracts of the combination of Foeniculum vulgare and Matricaria chamomilla using different solvents of increasing polarity in a Soxhlet extractor and evaluating their ovicidal, larvicidal, and cytotoxic activities. The most promising among all tested extracts was hexane extract. The ovicidal activity of the hexane PH2 extract resulted in a significant (p < 0.05) decrease in egg hatchability from 95.00 ± 6.16% to 15 ± 9.04% at doses ranging from 62.5 to 500 µg/mL. The larval mortality with the hexane extract ranged from 13.33 ± 3.3% to 93.33 ± 3.3% at doses ranging from 31.25 to 250 µg/mL, respectively. The LC₅₀ and LC₉₀ values of the larvicidal activity of the hexane extract were estimated to be 148.3 and 242.17 µg/mL, respectively, after 24 h of exposure. Similarly, the LC₅₀ values after 48 and 72 h of exposure were 124.93 and 100.3 µg/mL, respectively, against the third instar of Cx. pipiens. PH2 treatment of larvae resulted in histopathological changes such as degenerated epithelial cells and destruction of microvilli on the epithelial cells. The PH2 extract achieved a dose-dependent decrease in the rate of cell survival. The IC₅₀ value of PH2-treated HUVECs was 192.07 µg/mL after 24 h of incubation. The cells showed changes in cellular and nuclear morphology. In conclusion, the hexane extract of PH2 could be used in mosquito management programs.

Larvicidal Activity of Ethyl Acetate Extract of Derris elliptica Root against the Third-Instar Larvae of Cypermethrin-Resistant Aedes aegypti Offspring

Background:

Derris elliptica extracts have a high larvicidal potential against the laboratory strain of Aedes aegypti larvae, but the effect on offspring larvae of pyrethroid-resistant strains of the species is lack understood. This study aimed to determine the larvicidal activity of the ethyl acetate extract of tuba root against the third-instar larvae of the Cypermethrin-resistant Ae. aegypti offspring.

Methods:

The experimental study occupied four levels of ethyl acetate extract of D. elliptica namely 10, 25, 50, and 100 ppm, and each level was four times replicated. As many as twenty of healthy third-instar larvae, offspring of Cypermethrin-resistant Ae. aegypti were subjected to each experiment group. Larval mortality rate and lethal concentration 50% subject (LC₅₀) were calculated after 24 and 48 hours of exposure time.

Results:

Mortality of larvae increased directly proportional to the increase of extract concentration. Larval mortality rates after 24 and 48 hours of exposure were 40–67.5% and 62.5–97.5%, and LC₅₀ were 34.945 and 6.461ppm, respectively.

Conclusion:

The ethyl acetate extract of D. elliptica has the high effectiveness larvicidal potential against the third-instar larvae, offspring of the Cypermethrin-resistant Ae. aegypti. Isolation of the specific compound is necessarily done to obtain the active ingredient for larvicide formulation.

Chemo Suppressive and Curative Potential of Hypoestes forskalei Against Plasmodium berghei: Evidence for in vivo Antimalarial Activity

Background

The emergence of drug resistance together with the global burden of malaria triggers the necessity for the searching of new antimalarial agents. This study, therefore, was initiated to investigate the in vivo antimalarial activity of Hypoestes forskalei in mice based on the strong supported evidence from the ethnobotanical claims and the in vitro anti-plasmodial activity of the plant.

Methods

The 4-day suppressive (crude extract and fractions) and the Rane’s (n-butanol fraction) tests were used to evaluate the antimalarial activity of the plant. A cold maceration technique with 80% methanol was used for the crude extraction of the plant. The crude extract was then fractionated using solvents of different polarity (chloroform, n-butanol, and water).

Results

All the test doses of the crude extract as well as the fractions reduced parasitemia and prolonged mean survival time significantly (P<0.001) as compared to their negative control groups. Maximum parasitemia suppression effect (56%) was observed at the highest dose (600 mg/kg) of the crude extract during the 4-day suppressive test. Likewise, the n-butanol, chloroform, and aqueous fractions showed a percentage suppression of about 50, 38, and 19, respectively, at the dose of 600 mg/kg. Therefore, the n-butanol fraction showed the highest parasitemia suppression followed by the chloroform fraction and then the aqueous fraction. Moreover, the n-butanol fraction showed a significant curative effect (P<0.001) in Rane’s test with a percentage suppression of about 49 at a dose of 600 mg/kg.

Conclusion

The study has revealed that the plant has a promising antimalarial activity, the activity being more in the crude extract than the fractions. The highest antimalarial activity of the n-butanol fraction suggests that non-polar and medium polar principles could be responsible for the observed activity.

Biocontrol of mosquito vectors through herbal-derived silver nanoparticles: prospects and challenges

Mosquitoes spread several life-threatening diseases such as malaria, filaria, dengue, Japanese encephalitis, West Nile fever, chikungunya, and yellow fever and are associated with millions of deaths every year across the world. However, insecticides of synthetic origin are conventionally used for controlling various vector-borne diseases but they have various associated drawbacks like impact on non-targeted species, negative effects on the environment, and development of resistance in vector species by alteration of the target site. Plant extracts, phytochemicals, and their nanoformulations can serve as ovipositional attractants, insect growth regulators, larvicides, and repellents with least effects on the environment. Such plant-derived products exhibit broad-spectrum resistance against various mosquito species and are relatively cheaper, environmentally safer, biodegradable, easily accessible, and are non-toxic to non-targeted organisms. Therefore, in this review article, the current knowledge of phytochemical sources exhibiting larvicidal activity and their variations in response to solvents used for their extraction is underlined. Also, different methods such as physical, chemical, and biological for silver nanoparticle (AgNPs) synthesis, their mechanism of synthesis using plant extract, their potent larvicidal activity, and the possible mechanism by which these particles kill mosquito larvae are discussed. In addition, constraints related to commercialization of nanoherbal products at government and academic or research level and barriers from laboratory experiments to field trial have also been discussed. This comprehensive information can be gainfully employed for the development of herbal larvicidal formulations and nanopesticides against insecticide-resistant vector species in the near future. Graphical abstract.