Biological Activity of Root Extract <i>Decalepis hamiltonii</i> (Wight & Arn) against Three Mosquito Vectors and Their Non-Toxicity against the Mosquito Predators

Abstract

Bioactive molecules of plant origin play a significant role as defensive agents in different insect species. Chemical compounds in medicinal plants have been an exciting alternative to standard methods of controlling mosquito larvae. The present study evaluates the different solvent extracts of D. hamiltonii for toxicity against three different mosquito larvae. Bioassay revealed that the effect of the methanol extracts increased the larval mortality with increasing concentration. The highest larval mortality was observed in Culex quinquefasciatus with 98.33%, followed by 95 and 90% mortality in Aedes aegypti and Anopheles stephensi, at 24 h exposure. GC-MS analysis of methanol extract of D. hamiltonii showed six major peak compounds. They are benzaldehyde, 2-hydroxy-4-methoxy-(10.35%), dodecanoic acid (11.02%), n-hexadecanoic acid (21.05%), linoleic acid methyl ester (14.20%), oleic acid (21.04%), octadecanoic acid (22.21%). The level of α and β Carboxylesterases gets significantly decreased post-treatment with the methanol extract of D. hamiltonii in a dose-dependent manner.In contrast, glutathione S-transferase (GST) and cytochrome-P450 (CYP450) levels get up-lifted steadily when the dosage gets increased. The ratio of GST level has drastically proclaimed to in Ae. aegypti 0.702 mg/m Lin parallel to Cx. quiquefasciatus (0.656 mg/mL) and An. stephensi (0.812 mg/mL). Cytochrome P450 (CYP450) activity was observed to increase significantly post-treatment with the sub-lethal dosage of methanol extract of D. hamiltonii. Correspondingly, the non-target screening against the aquatic predators reveals that the crude root extracts and their derivatives are ecologically safe and less toxic. Overall, the present research highlights the chemical characterization of crude methanol extracts of D. hamiltonii, their insecticidal activity against the medically challenging pests, and their non-target activity delivers an ecologically safe, and target specific bio-active agents and suitable substitute for chemical pesticides.

Keywords

• <i>D. hamiltonii</i>
• methanol
• Carboxylesterases
• CYP450
• mosquito predators