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Larvicidal Activity and Phytochemical Profiling of Sweet Basil (Ocimum basilicum L.) Leaf Extract against Asian Tiger Mosquito (Aedes albopictus)

Applying larvicides to interrupt a mosquito’s life cycle is an important strategy for vector control. This study was conducted to evaluate the larvicidal properties of the hexane extract of sweet basil (Ocimum basilicum L.; family Lamiaceae) leaves against the wild strain of Asian tiger mosquito, Aedes albopictus (Skuse). Third instar larvae (20 larvae/replicate, n = 3) were exposed to different concentrations of the extract (6.25–200 µg/mL), and the mortality rate was recorded. Probit analysis showed that the median lethal concentration and 95% lethal concentration of the extract were 16.0 (10.9–22.1) and 53.0 (34.6–136.8) µg/mL, respectively, after 24 h exposure. Only the fractions F3, F4, and F5 from the column chromatography displayed high mortality rates of 91.7–100% at 25.0 µg/mL after 24 h exposure. Subsequent column chromatography from the pooled fraction yielded two active subfractions, H-F345-S2 and H-F345-S3, with mortality rates of 100% and 98.3 ± 2.9%, respectively, at 12.5 µg/mL. Gas chromatography–mass spectrometry analysis unveiled that methyl chavicol, 2-(2-butoxyethoxy)ethanol, cedrelanol, methyl eugenol, 2,4,di-tert-butylphenol, and phytol were the major components in both subfractions with some of them being reported as larvicidal compounds. The results suggest that sweet basil has substantial larvicidal activity against Ae. albopictus mosquito and is a potential source of naturally derived larvicide.