Chemical composition and evaluation of antioxidant and insecticidal activities of smoke from Azadirachta indica (neem) leaves

This study investigated the chemical composition, antioxidant, and insecticidal properties of leaf smoke from Azadirachta indica (neem) extracted with n-hexane and methanol. GC-MS analysis revealed that the n-hexane-trapped extract was dominated by methyl hexadecanoate (64.27%) and methyl stearate (25.86%). The methanol-trapped extract primarily contained 3,5-di-butylphenol (30.01%), methyl hexadecanoate (13.22%), and 1,2:15,16-diepoxy hexadecane (8.10%). The methanol extract exhibited 19.65% antioxidant activity at 152.20 µg/mL, whereas the n-hexane extract showed negligible results. In insecticidal assays against cockroaches, both extracts displayed significant repellent activity, increasing from initial levels to 81.24% (n-hexane) and 100% (methanol) after 60 minutes. At a 10% concentration, the methanol and n-hexane extracts achieved 100% and 80% mortality, respectively. The methanol extract demonstrated superior efficacy with an LC50 of 6.40% and an LT50 of 4.60 h at the lowest concentration (1.25%). Conversely, the n-hexane extract was less potent, reaching an LT50 only at 35 h. These findings indicate that A. indica leaf smoke is a rich source of bioactive compounds and a promising candidate for the development of natural insecticidal agents. KEY WORDS: Antioxidant, Insecticidal, Azadirachta indica (neem) leaf, Repellent, Smoke Bull. Chem. Soc. Ethiop. 2026, 40(6), 1309-1319.                                       DOI: https://dx.doi.org/10.4314/bcse.v40i6.11