Chemical composition and Insecticidal activity of essential oils of Cinnamomum zeylanicum, Citrus grandis, Citrus medica and Citrus sinensis leaves from Cameroon on Anopheles gambiae Giles, 1902

Mosquito resistance to conventional insecticides is a barrier to malaria prevention in endemic countries. This study proposes an alternative method for vector control, based on the use of essential oils from some plants from Cameroon. Essential oils were obtained by hydro-distillation of Cinnamomum zeylanicum, Citrus grandis, Citrus medica and Citrus sinensis leaves, using a Clevenger type apparatus. The determination of the chemical composition was made by Gas Chromatography (GC) and coupling of Gas Chromatography with Mass Spectrometry (GC/MS). Biological tests were performed on stage IV larvae and pupae of Anopheles gambiae s.l. according to WHO standard protocol. Essential oils from Ci. zeylanicum, C. grandis, C. sinensis and C. medica leaves are rich in ẞ-cubebene (78.10%), cis-decahydro-naphthalene (16,09%), Z-ẞ-ocimene (33.03%) and ẞ-pinene (20.69%) respectively. At 400 ppm, the oils of Citrus induce larval mortality (≥ 95%) and pupal mortality (≥ 94%) after 10 hours of exposure. At equal concentration, Ci. zeylanicum oil induced pupal and larval mortality of 30% and 100% respectively. The LC50 and LC95i. values showed that Ci. zeylanicum (Larvae: LC50 = 98.95 and LC95 = 159.80; Nymphs: LC50 = 489.2 and LC95 = 1820.78) is a good larvicide and C. sinensis (larvae: LC50 = 136.98; LC95 = 342.54; Nymphs: LC50 = 78.41; LC95 = 126.11) is a good nymphocide. The essential oils of these plants should be strongly recommended for the development of natural biocides.