Plant-based larvicidal agents: An overview from 2000 to 2018

Exploring the Biomedical Frontiers of Plant-Derived Nanoparticles: Synthesis and Biological Reactions

As contemporary technology advances, scientists are striving to identify new approaches to managing several diseases. Compared to the more popular physiochemical synthesis, the plant-derived combination of metallic nanoparticles using plant secondary metabolites as a precursor has a number of benefits, including low expenses, low energy consumption, biocompatibility, and medicinal usefulness. This study intends to explore the impacts of using plant-derived synthetic materials including metallic nanoparticles (NPs), emphasizing the benefits of their broad use in next-generation treatments for cancer, diabetes, Alzheimer's, and vector diseases. This comprehensive analysis investigates the potential of plant-derived remedies for diseases and looks at cutting-edge nanoformulation techniques aimed at addressing the function of the nanoparticles that accompany these organic substances. The purpose of the current review is to determine how plant extracts contribute to the synthesis of Silver nanoparticles (AgNPs), Gold nanoparticles (GtNPs), and platinum nanoparticles (PtNPs). It provides an overview of the many phytocompounds and their functions in biomedicine, including antibacterial, antioxidant, anticancer, and anti-inflammatory properties. Furthermore, this study placed a special focus on a range of applications, including drug delivery systems, diagnostics and therapy, the present benefits of nanoparticles (NPs), their biomedical uses in medical technology, and their toxicities.

Mosquito Larvicidal Activity and Cytotoxicity of the Extracts of Aromatic Plants from Malaysia

Despite ongoing control efforts, the mosquito population and diseases vectored by them continue to thrive worldwide, causing major health concerns. There has been growing interest in the use of botanicals as alternatives to insecticides due to their widespread insecticidal properties, biodegradability, and adaptability to ecological conditions. In this study, we investigated the larvicidal activity and cytotoxicity effects of solvent extracts from three aromatic plants-Curcuma longa (turmeric), Ocimum americanum (hoary basil), and Petroselinum crispum (parsley)-against Aedes albopictus. Subsequently, we examined the phytochemical composition of the extracts through gas chromatography-mass spectrometry (GC-MS) analysis. Results revealed that the hexane extracts of O. americanum and P. crispum exhibited the greatest larvicidal activity with the lowest median lethal concentration (LC₅₀) values (<30 µg/mL) at 24 h post-treatment, with the former found to be significantly less toxic towards African monkey kidney (Vero) cells. The GC-MS analysis of the said extract indicated the presence of different classes of metabolites, including phenylpropanoids, very long-chain alkanes, fatty acids and their derivatives, and terpenes, with the most abundant component being methyl eugenol (55.28%), most of which, have been documented for their larvicidal activities. These findings provide valuable insights into the potential use and development of bioinsecticides, particularly from O. americanum.

Evaluating the Sublethal Effects of Origanum vulgare Essential Oil and Carvacrol on the Biological Characteristics of Culex pipiens biotype molestus (Diptera: Culicidae)

Culex pipiens is a mosquito species complex spread worldwide that poses a serious threat to human health as the primary vector of West Nile virus. Its control is mainly based on larvicidal applications with synthetic insecticides on mosquito breeding sites. However, the excessive use of synthetic larvicides may provoke mosquito resistance issues and negative side effects to the aquatic environment and human health. Plant-derived essential oils, including those from the Lamiaceae family, can be eco-friendly alternative larvicidal agents causing acute larval toxicity and/or growth inhibitory effects on the developmental stages of mosquitoes through different modes of action. In the current laboratory study, we evaluated the sublethal effects of carvacrol-rich oregano essential oil and pure carvacrol on Cx. pipiens biotype molestus, the autogenous member of the Cx. pipiens species complex, after the exposure of 3rd-4th instar larvae to LC₅₀ concentrations. The short-term (24 h) larvicidal treatment with the sublethal concentrations of both tested materials exhibited an acute lethal effect on the exposed larvae as well as significant delayed mortality for surviving larvae and pupae. Larvicidal treatment with carvacrol reduced the longevity of the emerged males. In addition, the morphological abnormalities that were observed at the larval and pupal stage along with failed adult emergence indicate the potential growth inhibitory properties of the tested bioinsecticides. Our findings suggest that carvacrol and carvacrol-rich oregano oil are effective plant-based larvicides at doses lower than the acute lethal ones, thus promoting an environmentally friendly and more affordable perspective for their use against the WNV vector Cx. pipiens biotype molestus.

Evaluation of the mosquito larvicidal potential and comparative assessment of the juice of Lantana camara Linn and Ocimum gratissimum Linn

In the present study, the larvicidal efficacy of the juices of the weeds Lantana camara Linn (L. camara) and Ocimum gratissimum Linn (O. gratissimum) was evaluated against the larvae of the malaria vectors Aedes aegypti, Anopheles subpictus and Culex quinquefasciatus. The freshly prepared juices of leaves were prepared by grinding them and diluting them at concentrations of 25, 50, 75, and 100 ppm. Twenty larvae of each species were introduced in different sterile Petri dishes in aqueous media under a controlled environment for the assessment of biological activity. The larvicidal activity of both juices was evaluated at 6, 12 and 24 hr post-exposure time points by observing the movement of each larva. The obtained data were subjected to probit analysis to determine the lethal concentrations that kill 50% and 90% (LC50 and LC90) of the treated larvae. The results revealed a noticeable larvicidal activity following 24 h of exposure. The juice of L. camara leaves exhibited an LC50 range of 47.47-52.06 ppm and an LC90 range of 104.33-106.70 ppm. Moreover, for the juice of O. gratissimum leaves, the LC50 range was 42.94-44.91 ppm and the LC90 range was 105.11-108.66 ppm. Taken together, the results indicate that the juices of L. camara and O. gratissimum leaves may be useful as effective, economical and eco-friendly larvicidal agents. However, additional studies are needed to explore the bioactive components of the weeds that exhibit larvicidal activity along with their mode of action.

Mosquito-Borne Diseases and Their Control Strategies: An Overview Focused on Green Synthesized Plant-Based Metallic Nanoparticles

Mosquitoes act as vectors of pathogens that cause most life-threatening diseases, such as malaria, Dengue, Chikungunya, Yellow fever, Zika, West Nile, Lymphatic filariasis, etc. To reduce the transmission of these mosquito-borne diseases in humans, several chemical, biological, mechanical, and pharmaceutical methods of control are used. However, these different strategies are facing important and timely challenges that include the rapid spread of highly invasive mosquitoes worldwide, the development of resistance in several mosquito species, and the recent outbreaks of novel arthropod-borne viruses (e.g., Dengue, Rift Valley fever, tick-borne encephalitis, West Nile, yellow fever, etc.). Therefore, the development of novel and effective methods of control is urgently needed to manage mosquito vectors. Adapting the principles of nanobiotechnology to mosquito vector control is one of the current approaches. As a single-step, eco-friendly, and biodegradable method that does not require the use of toxic chemicals, the green synthesis of nanoparticles using active toxic agents from plant extracts available since ancient times exhibits antagonistic responses and broad-spectrum target-specific activities against different species of vector mosquitoes. In this article, the current state of knowledge on the different mosquito control strategies in general, and on repellent and mosquitocidal plant-mediated synthesis of nanoparticles in particular, has been reviewed. By doing so, this review may open new doors for research on mosquito-borne diseases.

Edible Plant Extracts against Aedes aegypti and Validation of a Piper nigrum L. Ethanolic Extract as a Natural Insecticide

The Aedes aegypti mosquito significantly impacts public health, with vector control remaining the most efficient means of reducing the number of arboviral disease cases. This study screened the larvicidal and pupicidal activity of common edible plant extracts. Piper nigrum L. (black pepper) extract production was optimized using accelerated solvent extraction (ASE) and validated following regulatory requirements using HPLC-PDA analytical methodology to quantify its major component-piperine. Larvicidal activity was determined for the standardized P. nigrum fruit ethanol extract (LC₅₀ 1.1 µg/mL) and piperine standard (LC₅₀ 19.0 µg/mL). Furthermore, 9-day residual activity was determined for the extract (4 µg/mL) and piperine (60 µg/mL), with daily piperine quantification. Semi-field trials of solid extract formulations demonstrated 24-day activity against Ae. aegypti larvae. Thus, the standardized P. nigrum extract emerges as a potential candidate for insecticide development to control the arboviral vector.

Essential Oils from Vietnamese Asteraceae for Environmentally Friendly Control of Aedes Mosquitoes

Mosquitoes, in addition to being a biting nuisance, are vectors of several pathogenic viruses and parasites. As a continuation of our work identifying abundant and/or invasive plant species in Vietnam for use as ecologically friendly pesticidal agents, we obtained the essential oils of Blumea lacera, Blumea sinuata, Emilia sonchifolia, Parthenium hysterophorus, and Sphaeranthus africanus; analyzed the essential oils using gas chromatographic techniques; and screened the essential oils for mosquito larvicidal activity against Aedes aegypti and Aedes albopictus. The most active larvicidal essential oils were B. sinuata, which was rich in thymohydroquinone dimethyl ether (29.4%), (E)-β-caryophyllene (19.7%), α-pinene (8.8%), germacrene D (7.8%), and α-humulene (4.3%), (24-h LC₅₀ 23.4 and 29.1 μg/mL) on Ae. aegypti and Ae. albopictus, respectively, and Emilia sonchifolia, dominated by 1-undecene (41.9%) and germacrene D (11.0%), (24-h LC₅₀ 30.1 and 29.6 μg/mL) on the two mosquito species. The essential oils of P. hysterophorus and S. africanus were also active against mosquito larvae. Notably, B. sinuata, P. hysterophorus, and S. africanus essential oils were not toxic to the non-target water bug, Diplonychus rusticus. However, E. sonchifolia essential oil showed insecticidal activity (24-h LC₅₀ 48.1 μg/mL) on D. rusticus. Based on these results, B. sinuata, P. hysterophorus, and S. africanus essential oils appear promising for further investigations.

Efficacy Evaluation of Oregano Essential Oil Mixed with Bacillus thuringiensis israelensis and Diflubenzuron against Culex pipiens and Aedes albopictus in Road Drains of Italy

Mosquito management programs in the urban environment of Italian cities mainly rely on larval control with conventional insecticides, primarily targeting the road drains that constitute the principal mosquito breeding sites encountered in public. The repeated utilization of synthetic insecticides may have adverse effects on non-targets and lead to resistance development issues, while the performance of biopesticides encounters limitations in field use. Botanical insecticides as single larval control agents or in binary mixtures with conventional insecticides have been extensively studied in the laboratory as an effective and eco-friendly alternative mosquito control method with promising results. The study herein concerns the investigation, for the first time under realistic conditions in the field, of the joint action of a carvacrol-rich oregano Essential Oil (EO) with two conventional insecticides, namely, the insect growth regulator diflubenzuron and the bio-insecticide Bacillus thuringiensis israelensis (B.t.i.), in road drains in Crevalcore city, Italy, against Culex pipiens and Aedes albopictus. According to the obtained results, the application of both plain EO and its mixtures with diflubenzuron and B.t.i. exerted very high efficacy in terms of immature mosquito population reduction over a two-week period. Three weeks after treatment, the performance of the oil and its mixtures diminished but remained high, while the addition of diflubenzuron potentiated the persistent action of the oil against Cx. pipiens. These findings are indicative of the potential of mixing carvacrol-rich EO with diflubenzuron and B.t.i. as an efficient eco-friendly alternative to mono-insecticide applications in road drains against Cx. pipiens and Ae. albopictus larvae.

Sublethal effects of oregano essential oil and its major compound carvacrol on biological parameters of Aedes albopictus (Diptera: Culicidae)

Mosquito management programs rely basically on the use of conventional synthetic larvicides. However, frequent applications and misuse of some synthetic insecticides have led to problems related to mosquito resistance development, harmful effects on human health and unacceptable environmental effects on non-target organisms. Recently, a growing number of phytochemicals has been tested as more eco-friendly larvicides against various mosquito species, exerting high efficacy with multiple modes of action. In the laboratory, we investigated for the first time the sublethal effects of oregano oil and its major compound carvacrol, against Aedes albopictus (Asian tiger mosquito), a mosquito of great medical importance. We determined the effects of short term (24h) exposure of 3rd- 4th larvae to LC₅₀ concentrations on survival and development of survived larvae until adulthood, as well as on fecundity, fertility, longevity and wing length of emerged adults. Only half of 24h survived larvae from oregano oil and carvacrol treatment finally reached adulthood. Abnormal shapes of dead larvae and pupae, and failed adult emergence were also observed, indicating a potential growth inhibitory activity of the tested materials. No particular effects from exposure to larvicidal LC₅₀ concentrations were recorded on life cycle parameters of successfully emerged adults. These findings suggest the tested oregano oil and carvacrol as sufficiently effective larvicides against Ae. albopictus at lower than the acutely toxic concentrations, promoting a more eco-friendly and less costly profile for these biopesticides.

Medicinal Plants of Solanum Species: The Promising Sources of Phyto-Insecticidal Compounds

Several medicinal plants have the potential to be a promising alternative pharmacological therapy for a variety of human illnesses. Many insects, including mosquitoes, are important vectors of deadly pathogens and parasites, which in the world's growing human and animal populations can cause serious epidemics and pandemics. Medicinal plants continue to provide a large library of phytochemicals, which can be used to replace chemically synthesized insecticides, and utilization of herbal product-based insecticides is one of the best and safest alternatives for mosquito control. Identifying new effective phyto-derived insecticides is important to counter increasing insect resistance to synthetic compounds and provide a safer environment. Solanum genus (Solanaceae family or nightshades) comprises more than 2500 species, which are widely used as food and traditional medicine. All research publications on insecticidal properties of Solanaceae plants and their phytoconstituents against mosquitoes and other insects published up to July 2020 were systematically analyzed through PubMed/MEDLINE, Scopus, EBSCO, Europe PMC, and Google Scholar databases, with focus on species containing active phytoconstituents that are biodegradable and environmentally safe. The current state of knowledge on larvicidal plants of Solanum species, type of extracts, target insect species, type of effects, name of inhibiting bioactive compounds, and their lethal doses (LC₅₀ and LC₉₀) were reviewed in this study. These studies provide valuable information about the activity of various species of Solanum and their phytochemical diversity, as well as a roadmap for optimizing select compounds for botanical repellents against a variety of vectors that cause debilitating and life-threatening human diseases.

Efficacy of metal nanoparticles as a control tool against adult mosquito vectors: A review

Presently, there is a need to develop effective and novel modes of control for mosquitoes, which remain a key driver of infectious disease transmission throughout the world. Control methods for these vectors have historically relied on a limited number of active ingredients (AIs) that have not experienced significant change in usage since the mid-20th century. The resulting development of widespread insecticide resistance has consequently increased the risk for future vector-borne disease outbreaks. Recently, metal nanoparticles have been explored for potential use in mosquito control due to their demonstrated toxicity against mosquitoes at all life stages. However, the majority of studies to date have focused on the larvicidal efficacy of metal nanoparticles with few studies examining their adulticidal potential. In this review, we analyze the current literature on green synthesized metal nanoparticles and their effect on adult mosquitoes.

Polymer-based nanostructures loaded with piperine as a platform to improve the larvicidal activity against Aedes aegypti

Piperine is an alkaloid extracted from the seed of Piper spp., which has demonstrated a larvicidal effect against Ae. aegypti. The incorporation of piperine into nanostructured systems can increase the effectiveness of this natural product in the control of Ae. aegypti larvae. In this study, we evaluated the effectiveness of piperine loaded or not into two nanostructured systems (named NS-A and NS-B) prepared by the nanoprecipitation method. The Ae. aegypti larvae were exposed to different concentrations of piperine loaded or not (2 to 16 ppm) and the mortality was investigated after 24, 48, and 72 hours. The nanostructures prepared were spherical in shape with narrow size distribution and great encapsulation efficiency. The lethal concentration 50 (LC₅₀) for non-loaded piperine were 13.015 ppm (24 hours), 8.098 ppm (48 hours), and 7.248 ppm (72 hours). The LC₅₀ values found for NS-A were 35.378 ppm (24 hours), 12.091 ppm (48 hours), and 8.011 ppm (72 hours), whereas the values found for NS-B were 21.267 ppm (24 hours), 12.091 ppm (48 hours), and 8.011 ppm (72 hours). Collectively, these findings suggested that non-loaded piperine caused higher larval mortality in the first hours of exposure while the nanostructured systems promoted the slow release of piperine and thereby increased the larvicidal activity over time. Therefore, loading piperine into nanostructured systems might be an effective tool to improve the larval control of vector Ae. aegypti.

Preparation of nanoemulsion of Cinnamomum zeylanicum oil and evaluation of its larvicidal activity against a main malaria vector Anopheles stephensi

PURPOSE

There is a growing need to use green and efficient larvicidal as alternatives for conventional chemicals in vector control programs. Nanotechnology has provided a promising approach for research and development of new larvicides. Larvicidal potential of a nanoemulsion of Cinnamomum zeylanicum essential oil reports against Anopheles stephensi.

METHODS

The nanoemulsion of was formulated in various ratios comprising of C. zeylanicum oil, tween 80, span 20 and water by stirrer. It was characterized by transmission electron microscopy (TEM) and dynamic light scattering (DLS). All components of C. zeylanicum essential oil were identified by GC-MS analysis. The larvicidal potential of the oil and its nanoformulation were evaluated against larvae of An. stephensi. The stability and durability of nanoemulsion was observed over a period of time.

RESULTS

Sixty one components in the oil were identified, cinnamaldehyde (56.803%) was the main component. The LC90 and LC50 values of C. zeylanicum essential oil were calculated as 49 ppm and 37 ppm, respectively. The nanoemulsion droplets were found spherical in shape. It was able to kill 100% of larvae in up to 3 days. It was stable after dilution and increased its larvicidal activity up to 32% compared with the essential oil.

CONCLUSIONS

A novel larvicide based on nanotechnology introduced. This experiment clearly showed increasing larvicidal activity and residual effect of the nanoformulation in comparison with the bulk essential oil. It could be concluded that this nanoemulsion may be considered as safe larvicide and should be subject of more research in this field.

GRAPHICAL ABSTRACT

Elucidation of larvicidal potential of metallic and environment friendly food-grade nanostructures against Aedes albopictus

To combat health challenges associated with mosquito-borne diseases, the larvicidal activity of metallic nanoparticles, food-grade polymeric nano-capsules and insecticides was investigated against larvae of Aedes albopictus as an effective alternate control approach. The Ae. albopictus was identified using sequencing and phylogenetic analyses of COXI, CYTB and ITS2 genes. The characterization of synthesized nanostructures was performed through Zetasizer, UV-VIS spectroscopy, atomic force microscopy, scanning electron microscopy and energy dispersive X-ray spectroscopy. The mosquito larvae were exposed to varying concentration of nanostructures and insecticides, and their percentage mortality was evaluated at different time intervals of 24 h and 48 h exposure. The highest efficacy was observed in zinc oxide nanoparticles (ZnO-NPs) and polymeric nanocapsules FG-Cur E-III (LC50 = 0.24 mg/L, LC90 = 0.6 mg/L) and (LC50 = 3.8 mg/L, LC90 = 9.33 mg/L), respectively, after 24 h; while (LC50 = 0.18 mg/L, LC90 = 0.43 mg/L) and (LC50 = 1.95 mg/L, LC90 = 6.46 mg/L), respectively, after 48 h against fourth instar larvae of Ae. albopictus. Ag, CuO, NiTiO3 and CoTiO3 nanoparticles evaluated in this study also showed promising larvicidal activity. Although ZnO-NPs proved to be effective larvicides, their possible toxicity (producing ROS species) can limit their use. The curcumin nanostructures (FG-Cur E-III) stabilized by food-grade materials are thought to exert their larvicidal activity by binding to sterol carrier protein-2, and depriving the larvae from the essential dietary cholesterol, and bears effective larvicidal potential as safe alternative for chemical larvicides, due to their environment friendly, food-grade and easy biodegradability.

Lantana camara Essential Oils from Vietnam: Chemical Composition, Molluscicidal, and Mosquito Larvicidal Activity

Lantana camara is a troublesome invasive plant introduced to many tropical regions, including Southeast Asia. However, the plant does hold promise as a source of essential oils that may be explored for potential use. Fresh water snails such as Pomacea canaliculata, Gyraulus convexiusculus, and Tarebia granifera can be problematic agricultural pests as well as hosts for parasitic worms. Aedes and Culex mosquitoes are notorious vectors of numerous viral pathogens. Control of these vectors is of utmost importance. In this work, the essential oil compositions, molluscicidal, and mosquito larvicidal activities of four collections of L. camara from north-central Vietnam have been investigated. The sesquiterpene-rich L. camara essential oils showed wide variation in their compositions, not only compared to essential oils from other geographical locations (at least six possible chemotypes), but also between the four samples from Vietnam. L. camara essential oils showed molluscicidal activities comparable to the positive control, tea saponin, as well as other botanical agents. The median lethal concentrations (LC₅₀ ) against the snails were 23.6-40.2 μg/mL (P. canaliculata), 7.9-29.6 μg/mL (G. convexiusculus), and 15.0-29.6 μg/mL (T. granifera). The essential oils showed good mosquito larvicidal activities with 24-h LC₅₀ values of 15.1-29.0 μg/mL, 26.4-53.8 μg/mL, and 20.8-59.3 μg/mL against Ae. aegypti, Ae. albopictus, and Cx. quinquefasciatus, respectively. The essential oils were more toxic to snails and mosquito larvae than they were to the non-target water bug, Diplonychus rusticus (24-h LC₅₀ =103.7-162.5 μg/mL). Sesquiterpene components of the essential oils may be acting as acetylcholinesterase (AChE) inhibitors. These results suggest that the invasive plant, L. camara, may be a renewable botanical pesticidal agent.

Effects of a solid formulation containing lectin-rich fraction of Moringa oleifera seeds on egg hatching and development of Aedes aegypti larvae

The measures currently used to minimize the spread of arboviruses, comprising dengue, Chikungunya, and Zika virus, involve controlling the size of population of the mosquito Aedes aegypti. However, the search for formulations containing new insecticides is gaining pace due to reports of mosquito populations showing resistance to commonly used compounds. In this study, tablets containing a protein fraction of Moringa oleifera seeds enriched in the WSMoL lectin, known to show larvicidal and ovicidal activities against A. aegypti, were developed. The compatibility between the fraction and the excipients used in obtaining the tablets was evaluated by thermogravimetry (TG), differential scanning calorimetry (DSC), and Fourier transform infrared (FTIR) absorption spectroscopy. The larvicidal and ovicidal activities of the resulting tablets [5%, 10%, and 15% (w/w) of the fraction] were evaluated, as well as their effect on mosquito oviposition. Assays were also performed using a placebo tablet. According to the TG, DSC, and FTIR results, the protein composition of the fraction did not change when mixed with the components of the formulation. Tablets containing 10% and 15% WSMoL-rich fraction caused mortality of 42.5% and 95% of the larvae after 48 h, respectively, with larvae incubated with these tablets showing reduced acetylcholinesterase activity. All tablets inhibited egg hatching after 72 h (36-74%), and tablets containing 15% fraction were found to exert a repellent effect on oviposition. Our results show that the formulation developed in this study interfered with the life cycle of A. aegypti, and thus show potential for use in the control of this mosquito.

Larvicidal and Enzymatic Inhibition Effects of Annona muricata Seed Extract and Main Constituent Annonacin against Aedes aegypti and Aedes albopictus (Diptera: Culicidae)

The mosquitoes Aedes aegypti and Aedes albopictus are vectors of arboviruses that cause dengue, zika and chikungunya. Bioactive compounds from plants are environmentally sustainable alternatives to control these vectors and thus the arboviruses transmitted by them. The present study evaluated the larvicidal activity of an acetogenin-rich fraction (ACERF) and its main constituent annonacin obtained from Annona muricata seeds on Ae. aegypti and Ae. albopictus. The larvicidal assays were performed using different concentrations to calculate the LC50 and LC90 values observed 24 h after exposure to the treatment. Annonacin was more active against Ae. aegypti (LC50 2.65 μg·mL-1) in comparison with Ae. albopictus (LC50 8.34 μg·mL-1). In contrast, the acetogenin-rich fraction was more active against Ae. albopictus (LC50 3.41 μg·mL-1) than Ae. aegypti (LC50 12.41 μg·mL-1). ACERF and annonacin treated larvae of Ae. aegypti and Ae. albopictus showed significant differences in the inhibition of their metabolic enzymes when compared to untreated larvae. The results demonstrate the relevant larvicidal action of the acetogenin-rich fraction and annonacin showing the potential to develop new products for the control of Ae. aegypti and Ae. albopictus.