Seasonal variation in the chemical composition and larvicidal activity against Aedes aegypti L. of essential oils from Brazilian Amazon

Abstract

Arthropod-borne viral diseases are important public health threats in tropical countries. In the Americas, diseases such as Dengue, Zika, Chikungunya, Mayaro, and Yellow fever, which are mainly transmitted by Aedes aegypti L. are responsible for high rates of morbidity and mortality in the populations. The incidence of those viruses has increased in the last few years, due to the decrease of vector control programs, as well as, the resistance of this vector in front of many products that have been used in this proposal. Plant-based products such as essential oils are a promising alternative for Ae. aegypti control. In this context, the present work aims to investigate the seasonality effect on the larvicidal potential and safety of essential oils from 4 endemic plants of the Brazilian Amazon, as well as to verify their larvicidal activity and safety. The species were collected in the rainy and dry periods (Eugenia uniflora L., Lantana camara L., Ocimum basilicum L., Plectranthus neochilus Schlrt.). The essential oils were extracted by hydrodistillation and chemical composition was determined by gas chromatography coupled to mass spectrometry. The larvicidal activity was performed according to the methodology recommended by the World Health Organization. The safety of the oil use was evaluated against two non-target organisms: Artemia salina Leach and Danio rerio Hamilton Buchanan. Essential oils of E. uniflora, L. camara, O. basilicum, P. neochilus, presented as major compounds, in both collection periods, the substances Curzerene, Germacrene D, Methyl chavicol and, Caryophyllene, respectively. However, showed a qualitative and quantitative variation of this composition. All oils showed promising results against Ae. aegypti larvae with LC₅₀ between 41.7 and 275.8 μg/mL. They were efficient against Ae. aegypti but showed high toxicity to non-target organisms, requiring additional safety studies. Despite these results showing that those essential oils are not ideal larvicides because they presented toxicity to non-target organisms, bioprospection is a promising tool to help reduce the dissemination of arboviruses, and they can use in artificial breeders of Ae. aegypti larvae, where water will not be reused for human consumption or have other cohabiting organisms.

Keywords: Acute toxicity; Arboviruses; Artemia salina; Danio rerio; Vector control.