Phytochemistry and larvicidal activity of Spermacoce latifolia Aubl. (Rubiaceae) in the control of Aedes aegypti L. (Culicidae)

Abstract

In the search for alternative ways to control Aedes aegypti with minimal environmental impact and in a manner that preserves human health, this study sought to evaluate the larvicidal effect of the invasive and antioxidant Spermacoce latifolia plant by performing a phytochemical study. Phytochemical screenings were done according to characterization reactions and thin layer chromatography. Phenolics compounds content (Folin-Ciocalteu's) and flavonoids (AlCl₃) spectrophotometric was performed, and the antioxidant activity was determined by the 2,2-diphenyl-1-picrylhydrazyl (DPPH). The phytochemical results revealed the presence of phenolic, flavonoid, tannin, steroid, free triterpene, coumarin, and alkaloid compounds. The content of total phenols (TPs) (482.7 ± 1.8 mg mgGA g^-1) and flavonoids (165.4 ± 1.5 mg QE g^-1) accounted for the antioxidant activity of 150 µg.mL^-1 methanolic extract. In the proposed bioassays, groups of 25 third-stage larvae were challenged at different concentrations of plant crude extract (1.0, 0.5, 0.25, and 0.1 g L^-1) of weight per volume in four replicates. In multiple concentration tests, the concentrations were selected to range from 0% to 100% mortality after 24 hours of contact with the solution. Toxicity was defined as the inhibition or total inactivity of the larvae. It was concluded that the methanol extract had an LC₅₀ of 0.62 g L^-1, indicating its potential use as a larvicide against A. aegypti and linking its activity to its phenolic and flavonoid components.