Insecticidal Activities of Some Tropical Plants Extracts against Malaria Mosquito, Anopheles gambae Giles (Diptera: Culicidae)

Abstract

Anopheles mosquitoes are the primary vectors responsible for transmitting malaria-causing protozoans that affect populations worldwide. The use of synthetic insecticides to control mosquito populations can result in environmental pollution, human health risks, and depletion of the ozone layer. Consequently, there is a growing interest in identifying alternatives to synthetic insecticides. Botanical insecticides, which are inexpensive, readily available, and environmentally friendly, have emerged as viable options. This study investigated the insecticidal effects of methanol, ethanol, n-hexane, and acetone crude leaf extracts from Moringa oleifera, Eucalyptus citriodora, Mentha piperita, Azadirachta indica, and Andrographis paniculata on both adult and larval stages of Anopheles gambiae. Fresh leaves of the selected plants were collected, air-dried, and ground into powders. These powdered leaves were then extracted using absolute ethanol, methanol, n-hexane, and acetone at 60 °C in a Soxhlet extractor. Extract concentrations of 100, 150, 200, 250, and 300 ppm were prepared and tested against An. gambiae larvae and adults, with mortality recorded after 24 hours of exposure. The results demonstrated that ethanol and methanol extracts exhibited strong insecticidal activity, achieving 100% larval mortality at concentrations of 200, 250, and 300 ppm, and 100% adult mortality at 300 ppm. In contrast, n-hexane and acetone extracts showed limited activity against adult An. gambiae. Among the extracts tested, A. indica ethanol extract was the most potent, inducing 100% adult mortality at 300 ppm and complete larval mortality at 200 ppm. These findings indicate that leaf extracts of the tested plants, particularly A. indica, have significant potential for controlling both larval and adult An. gambiae. They may therefore serve as effective, eco-friendly alternatives to synthetic insecticides.