Nano-emulsification Enhances the Larvicidal Potential of the Essential Oil of Siparuna guianensis (Laurales: Siparunaceae) Against Aedes (Stegomyia) aegypti (Diptera: Culicidae)

Tiny Green Army: Fighting Malaria with Plants and Nanotechnology

Malaria poses a global threat to human health, with millions of cases and thousands of deaths each year, mainly affecting developing countries in tropical and subtropical regions. Malaria's causative agent is Plasmodium species, generally transmitted in the hematophagous act of female Anopheles sp. mosquitoes. The main approaches to fighting malaria are eliminating the parasite through drug treatments and preventing transmission with vector control. However, vector and parasite resistance to current strategies set a challenge. In response to the loss of drug efficacy and the environmental impact of pesticides, the focus shifted to the search for biocompatible products that could be antimalarial. Plant derivatives have a millennial application in traditional medicine, including the treatment of malaria, and show toxic effects towards the parasite and the mosquito, aside from being accessible and affordable. Its disadvantage lies in the type of administration because green chemical compounds rapidly degrade. The nanoformulation of these compounds can improve bioavailability, solubility, and efficacy. Thus, the nanotechnology-based development of plant products represents a relevant tool in the fight against malaria. We aim to review the effects of nanoparticles synthesized with plant extracts on Anopheles and Plasmodium while outlining the nanotechnology green synthesis and current malaria prevention strategies.

Promising Larvicidal Effects of Nanoliposomes Containing Carvone and Mentha spicata and Tanacetum balsamita Essential Oils Against Anopheles stephensi

PURPOSE

The use of synthetic pesticides to control the spread of mosquito-borne diseases has caused environmental pollution and insecticide resistance in mosquitoes. Developments of new green insecticides have thus received more attention to overcome these problems.

METHODS

Nanoliposomes containing carvone and essential oils were first prepared. The nanoliposome physicochemical characteristics (particle size, morphology, and successful loading) were then evaluated by Dynamic Light Scattering (DLS), Transmission Electron Microscopy (TEM), and the Attenuated Total Reflection-Fourier Transform InfraRed (ATR-FTIR) analyses. Larvicidal effects of carvone, Mentha spicata, and Tanacetum balsamita essential oils were investigated against the main malaria vector, Anopheles stephensi, in non-formulated and nanoformulated states.

RESULTS

The larvicidal effects of nanoformulated states were significantly more potent (7.2 folds, 3.5 folds, and 8 folds) than non-formulated states. Nanoliposomes containing M. spicata and T. balsamita essential oils with particle sizes of 175 ± 8 and 184 ± 5 nm showed the best efficacies (LC50 values = 9.74 and 9.36 μg/mL).

CONCLUSION

The prepared samples could be used as new green potent larvicides against An stephensi mosquito in further field trials. It is also recommended to investigate their efficacies against other mosquitoes.

Larvicidal properties of terpenoid-based nanoemulsions against the dengue vector Aedes aegypti L. and their potential toxicity against non-target organism

The development of insecticide resistance in mosquitoes of public health importance has encouraged extensive research into innovative vector control methods. Terpenes are the largest among Plants Secondary Metabolites and have been increasingly studied for their potential as insecticidal control agents. Although promising, terpenes are insoluble in water, and they show low residual life which limits their application for vector control. In this study, we developed and evaluated the performances of terpenoid-based nanoemulsions (TNEs) containing myrcene and p-cymene against the dengue vector Aedes aegypti and investigated their potential toxicity against non-target organisms. Our results showed that myrcene and p-cymene showed moderate larvicidal activity against mosquito larvae compared to temephos an organophosphate widely used for mosquito control. However, we showed similar efficacy of TNEs against both susceptible and highly insecticide-resistant mosquitoes from French Guyana, hence suggesting an absence of cross-resistance with conventional insecticides. We also showed that TNEs remained effective for up to 45 days in laboratory conditions. The exposure of zebrafish to TNEs triggered behavioral changes in the fish at high doses but they did not alter the normal functioning of zebrafish organs, suggesting a good tolerability of non-target organisms to these molecules. Overall, this study provides new insights into the insecticidal properties and toxicity of terpenes and terpenoid-based formulations and confirms that TNE may offer interesting prospects for mosquito control as part of integrated vector management.

Nanoliposomal Trachyspermum ammi (L) sprague essential oil for effective control of malaria mosquito larvae, Anopheles stephensi Liston

Controlling mosquito vectors at immature stages using larvicides is a practical strategy to stave off mosquito-borne diseases such as malaria. Developing nanoliposomes bearing essential oil is a promising approach to improving the efficacy and stability of EOs-derived larvicides. The main aim of this investigation was to assess the efficacy of nanoliposome containing Trachyspermum ammi L. EO (TAEO-NL) as a new potential formulation to control Anopheles stephensi Liston (Diptera, Culicidae) mosquito larvae. The chemical constituents of T. ammi L. essential oil (TAEO) were first investigated using gas chromatography-mass spectrometry (GC-MS) analysis; its dominant component (48.22%) was thymol. TAEO-NL with a particle size of 54.6 ± 5 nm and zeta potential of -18 ± 0.5 mV were then prepared using the ethanol injection method. Besides, the successful loading of TAEO was confirmed using Attenuated Total Reflection-Fourier Transform Infra-Red (ATR-FTIR) spectroscopy analysis. A significant difference (P < 0.05) was observed in the efficacy of TAEO-NL and TAEO with lethal concentration 50% (LC50) values of 14.09 and 59.47 μg/mL against An. stephensi larvae. However, free nanoliposomes show negligible larvicidal effects (<5%). This nano-formulation could thus be suggested as a green product against insects to impede transmission of deadly infectious diseases with possible field applicability scope.

Nanoliposomes containing three essential oils from the Artemisia genus as effective larvicides against Aedes aegypti and Anopheles stephensi

Aedes aegypti and Anopheles stephensi have challenged human health by transmitting several infectious disease agents, such as malaria, dengue fever, and yellow fever. Larvicides, especially in endemic regions, is an effective approach to the control of mosquito-borne diseases. In this study, the composition of three essential oil from the Artemisia L. family was analyzed by Gas Chromatography-Mass Spectrometry. Afterward, nanoliposomes containing essential oils of A. annua, A. dracunculus, and A. sieberi with particle sizes of 137 ± 5, 151 ± 6, and 92 ± 5 nm were prepared. Besides, their zeta potential values were obtained at 32 ± 0.5, 32 ± 0.6, and 43 ± 1.7 mV. ATR-FTIR analysis (Attenuated Total Reflection-Fourier Transform InfraRed) confirmed the successful loading of the essential oils. Moreover, The LC50 values of nanoliposomes against Ae. aegypti larvae were 34, 151, and 197 µg/mL. These values for An.stephensi were obtained as 23 and 90, and 140 µg/mL, respectively. The results revealed that nanoliposomes containing A. dracunculus exerted the highest potential larvicidal effect against Ae. aegypti and An. stephensi, which can be considered against other mosquitoes.

Nanoliposomes containing limonene and limonene-rich essential oils as novel larvicides against malaria and filariasis mosquito vectors

Background

Mosquito-borne diseases such as malaria and encephalitis are still the cause of several hundred thousand deaths annually. The excessive use of chemical insecticides for transmission control has led to environmental pollution and widespread resistance in mosquitoes. Botanical insecticides' efficacies improvement has thus received considerable attention recently.

Methods

The larvicidal effects of three essential oils from the Citrus family and limonene (their major ingredient) were first investigated against malaria and filariasis mosquito vectors. An attempt was then made to improve their efficacies by preparing nanoliposomes containing each of them.

Results

The larvicidal effect of nanoformulated forms was more effective than non-formulated states. Nanoliposomes containing Citrus aurantium essential oil with a particle size of 52 ± 4 nm showed the best larvicidal activity (LC₅₀ and LC₉₀ values) against Anopheles stephensi (6.63 and 12.29 µg/mL) and Culex quinquefasciatus (4.9 and 16.4 µg/mL).

Conclusion

Due to the green constituents and high efficacy of nanoliposomes containing C. aurantium essential oil, it could be considered for further investigation against other mosquitoes’ populations and field trials.

The Potential of Biologically Active Brazilian Plant Species as a Strategy to Search for Molecular Models for Mosquito Control

Natural products are a valuable source of biologically active compounds and continue to play an important role in modern drug discovery due to their great structural diversity and unique biological properties. Brazilian biodiversity is one of the most extensive in the world and could be an effective source of new chemical entities for drug discovery. Mosquitoes are vectors for the transmission of dengue, Zika, chikungunya, yellow fever, and many other diseases of public health importance. These diseases have a major impact on tropical and subtropical countries, and their incidence has increased dramatically in recent decades, reaching billions of people at risk worldwide. The prevention of these diseases is mainly through vector control, which is becoming more difficult because of the emergence of resistant mosquito populations to the chemical insecticides. Strategies to provide efficient and safe vector control are needed, and secondary metabolites from plant species from the Brazilian biodiversity, especially Cerrado, that are biologically active for mosquito control are herein highlighted. Also, this is a literature revision of targets as insights to promote advances in the task of developing active compounds for vector control. In view of the expansion and occurrence of arboviruses diseases worldwide, scientific reviews on bioactive natural products are important to provide molecular models for vector control and contribute with effective measures to reduce their incidence.

Essential oils and their chemical constituents against Aedes aegypti L. (Diptera: Culicidae) larvae

This review focused on the toxicity of essential oils and their constituents against Aedes aegypti L. (Diptera, Culicidae) larvae, a key vector of important arboviral diseases, such as dengue, chikungunya, zika, and yellow fever. This review is based on original articles obtained by searching major databases in the last six years. Our literature review shows that 337 essential oils from 225 plant species have been tested for larvicidal bioactivity. More than 60% of these essential oils were considered active (LC₅₀<100 µg/mL). Most species belong to the families Lamiaceae (19.3%), Lauraceae (9.9%), and Myrtaceae (9.4%). The plants studied for their larvicidal activity against A. aegypti were mainly collected in India and Brazil (30 and 20%, respectively) and the parts of the plants most used were the leaves. Less than 10% of essential oils were evaluated for toxicity against non-target organisms and with the aim to demonstrate safe use. The most used plant parts are leaves and the main compounds of essential oils were described. The most active essential oils are rich in sesquiterpene hydrocarbons, oxygenated sesquiterpenes, and monoterpene hydrocarbons. Here, factors affecting bioactivity (chemical composition, plant parts, and harvesting site) of essential oils and their constituents, as well as safety to non-target organisms are discussed. Essential oils have considerable potential against A. aegypti. This review shows that essential oils might be used to control arboviruses, and further studies on safety and formulations for application in the field should be performed.

Larvicidal Activity of Essential Oils Against Aedes aegypti (Diptera: Culicidae)

The Aedes aegypti is responsible for the transmission of arboviruses, which compromise public health. In the search for synthetic product alternatives, essential oils (OEs) have been highlighted by many researchers as natural insecticides. This systematic review (SR) was performed according to PRISMA guidelines (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) and its objective was to evaluate studies addressing OEs with larvicidal properties against Ae. aegypti, through electronic database searches (Pubmed, Science Direct and Scielo), covering an overview of the plant sources OEs, which plant parts were used, the extraction methods, analytical techniques, major and/or secondary constituents with greater percentages, as well as the LC50s responsible for larval mortality. Following study analysis, plants distributed across 32 families, 90 genera and 175 species were identified. The Lamiaceae, Myrtaceae, Piperaceae, Asteraceae, Rutaceae, Euphorbiaceae and Lauraceae families obtained the highest number of species with toxic properties against larvae from this vector. Practically all plant parts were found to be used for OE extraction. Hydrodistillation and steam distillation were the main extraction methods identified, with GC-MS/GC-FID representing the main analytical techniques used to reveal their chemical composition, especially of terpene compounds. In this context, OEs are promising alternatives for the investigation of natural, ecologically correct and biodegradable insecticides with the potential to be used in Ae. aegypti control programs.