Degradation evaluation and toxicity profile of bilobol, a promising eco-friendly larvicide

Abstract

Aedes aegypti is the main arbovirus vector transmitting chikungunya, Zika and dengue. The current vector control strategies are limited due to multiple insecticide resistance, deleterious impacts on the environment, and toxicity to non-target organisms. Bilobol, an alkylresorcinol isolated from the plant species Schinus terebinthifolia, demonstrated larvicidal activity against Aedes aegypti (LC₅₀ 7.67 mg/L in less than 24 h). To ensure that bilobol presents a viable alternative as an eco-friendly larvicide, this study aimed to explore the degradation process and acute toxicity of this alkylresorcinol in zebrafish, a non-target organism. A quantification method with validated parameters was developed and used to evaluate bilobol degradation in water over time. The Fish Embryo Toxicity (FET) test was applied to evaluate the acute toxicity of bilobol together with its degradation derivates. Results demonstrated that bilobol gradually degrades over time and almost completely disappears after 96 h, turning into small aliphatic chains which are less toxic than bilobol in its fundamental form. Therefore, it was possible to conclude that bilobol does not present significant toxicity to zebrafish embryos nor does it show signs of persistence in the environment. Additionally, bilobol can be found in high quantities not only in S. terebinthifolia, but also in cashew nut industry waste. Thus, bilobol constitutes an alternative environmentally friendly insecticide because it is not persistent, has indications of low toxicity to non-target organisms and presents a way to exploit massive quantities of material discarded by the food industry.

Keywords: Acute toxicity; Aedes aegypti; Bilobol; Bilobol quantification; Biodegradation; Larvicidal activity; Zebrafish.