Phytochemical Analysis and in-vitro Larvicidal Effect of Ethanolic Leaf Extract of Hyptis suaveolens against the 4th Instar Larvae of Anopheles gambiae

Abstract

This study evaluated the phytochemical composition and in vitro larvicidal activity of ethanolic leaf extract of Hyptis suaveolens against fourth-instar larvae of Anopheles gambiae. Fresh leaves of H. suaveolens were collected, washed, air-dried under shade, pulverised and extracted by maceration using 70% ethanol. The chemical constituents of the extract were assessed using gas chromatography-mass spectrometry. Larvicidal activity was tested under laboratory conditions at five extract concentrations: 10%, 20%, 30%, 40% and 50%. Each treatment was replicated three times, with 20 fourth-instar larvae introduced into each replicate. Larval mortality was recorded after 3, 6, 9, 12 and 24 hours of exposure. Lethal concentration and lethal time values were estimated using probit regression analysis, while mortality data were analysed using one-way analysis of variance and Pearson chi-square test at a significance level of p ≤ 0.05. The GC-MS analysis identified 25 compounds in the leaf extract. Squalene was the most abundant compound, with a peak area of 30.70%, whereas 1,4-Bis(trimethylsilyl)benzene had the lowest peak area of 0.33%. Larval mortality increased with extract concentration and exposure duration. The lowest mortality was recorded at 10% concentration, while 100% mortality was observed at 50% concentration after 24 hours. The estimated LC50 and LC90 values were 27.78 and 41.65, respectively. The LT50 and LT90 values were 15.59 hours and 104.82 hours, respectively. These findings indicate that ethanolic leaf extract of H. suaveolens showed concentration- and time-dependent larvicidal activity against fourth-instar larvae of A. gambiae under laboratory conditions.