Marching towards bioeconomy: Larvicidal effect of three indigenous plant extracts from Sri Lanka—Garcinia quaesita, Garcinia zeylanica, and Coleus hadiensis on dengue vector Aedes aegypti

Abstract

Bioeconomy would be a beneficial solution for funding through the rational use of finances and human resources in order to achieve better productivity and fruitfulness of mosquito control programs. Synthetic insecticides are widely used to repress mosquitoes. However, it instigates problems such as insecticide resistance among mosquitoes such as developing resistance, bio-accumulation, and ecosystem destabilization. Natural plant-based products are a healthy alternative to use as mosquito larvicides. The country has to spend a considerable cost for buying synthetic insecticides too. Therefore, the present study was undertaken to evaluate larvicidal efficacy of Garcinia zeylanica, Garcinia quaesita, and Coleus hadiensis against Aedes aegypti mosquito larvae. Fresh leaves of plants were collected, and the aqueous crude extract was prepared. Phytochemicals were extracted using refluxing technique. A concentration series of crude extract of leaves were prepared separately from 20 to 100 mg/L. Batches of each containing 100 third instar larvae of Ae. aegypti were used for larval bioassays. Ae. aegypti mosquito larvae were evaluated in accordance with the guidelines of World Health Organization. The experimental setup was repeated four times at each concentration. Probit analysis was used to evaluate the relationship of mortality with the concentration of aqueous crude extract. The G. zeylanica and G. quaesita leaf extracts showed a dose-dependent effect against Ae. aegypti larvae after the 24 and 48 h exposure period. Interestingly, C. hadiensis did not show any dose-dependent effect against A. aegypti mosquito larvae. The percentage mortality rates have shown a significant variance among different concentrations (P = 0.000). The recorded LC₅₀ and LC₉₀ for aqueous crude extract of G. zeylanica were 27.167 and 52.861 g/L, respectively, and LC₅₀ and LC₉₀ for aqueous crude extract of G. quaesita were 36.841 and 76.036 g/L, respectively, after 24 h of exposure period. The G. zeylanica and G. quaesita plant's high larvicidal activity is supported by the presence of phytochemicals such as saponins, steroids, flavonoids, and phenol, which showed combination effects in terms of larvicidal action to mosquito larvae. Hence, there is a potential of G. zeylanica and G. quaesita aqueous leaf extracts as a key source for the development of an environment-friendly plant-based larvicide against Ae. aegypti. Hence, this warrants vector control entities to re-think “biological wealth for economic prosperity” with environmentally friendly country-wide control approaches for medically important disease vectors.