Insecticidal efficacy of Lippia adoensis Hochst extract and fractions on larvae and adults Anopheles gambiae Giles and chemical profiling of active fractions by UHPLC-MS/MS

Abstract

Abstract Background The control of Anopheles gambiae , a major malaria vector, has traditionally relied on synthetic insecticides, which pose environmental risks and are harmful to humans and animals. This study aimed to evaluate the efficacy of the leaf methanol extract of Lippia adoensis and its fractions obtained by column chromatography against Anopheles gambiae larvae and adults, and to analyze the chemical profiles of the most active extracts using UPLC-MS/MS. Methods The leaf powder of L. adoensis was extracted with methanol by percolation and fractionation of the obtained crude extract via open-column chromatography produced five fractions. These fractions were tested against fourth instar larvae of A. gambiae at concentrations of 125, 250, 500, and 1000 ppm, following WHO guidelines. Adulticidal activity was evaluated in CDC bottles at concentrations ranging from 125 to 1000 ppm. Mortality was recorded after 24 h for larvae and 1 and 24 h for adults. UHPLC-MS/MS analysis identified the chemical profiles of the active extracts. Results The methanol crude extract demonstrated strong larvicidal activity with an LC 50 of 18.14 ppm. Fraction F1 showed the highest adulticidal activity with an LC 50 of 223.34 ppm after 24 h. UPLC-MS/MS analysis led to the identification of 19 compounds with flavonoids as major class of bioactive compounds. Conclusion L. adoensis leaf methanol extract and its fractions, especially F1, exhibit significant activity against A. gambiae larvae and adults. These findings highlight L. adoensis as a promising source of bio-insecticides for malaria vector control, with flavonoids potentially playing a key role in its insecticidal effects.