Chemical Composition and Ovicidal, Larvicidal and Pupicidal Activity of Ocimum basilicum Essential Oil against Anopheles gambiae. (Diptera: Culicidae)

Background: Malaria remains a serious Public Health issue in the sub-Saharan regions. Although Anopheles gambiae (main malaria vector) has developed resistance against commonly used insecticides, the emergence of this resistance as well as the pollution of the environment by these chemicals have led to the use of plant-derived products such as essential oils.

Aim: This study aimed to characterize and investigate in laboratory bioassays the ovicidal, larvicidal and pupicidal activities of Ocimum basilicum essential oil against aquatic stages of Anopheles gambiae, the main malaria vector in Cameroon.

Methods: Essential oils of O. basilicum fresh leaves were extracted by hydrodistillation, characterized by gas chromatography coupling mass spectrometry (GC-MS) and tested against An. gambiae eggs, larvae and pupal stages in laboratory bioassays.

Results: With an overall yield of 0.31% (w/w), the essential oil of O. basilicum fresh leaves revealed the presence of 29 compounds by GC-MS. Monoterpenes were the main group of compounds found with 1-8 Cineol (33.9%), β-Pinene 16.09%), Terpineol (11.21%) and α-Pinene (5.65%) as the main ingredients. These compounds demonstrated an efficient toxic effect against the aquatic stages of An. gambiae with no egg hatching after 24 hours exposure at >30 ppm. The LC50 values of the essential oil were respectively obtained one hour and 24 hours post-exposure for first (29.41 and 24.7 ppm), second (34.7 and 17.6 ppm), third (34.7 and 20 ppm) and fourth (45.29 and 23.5 ppm) instars larvae and the pupal stage (45.88 and 36.47 ppm) of An. gambiae.

Conclusion: The essential oil of O. basilicum demonstrated a good efficacy against the aquatic stages of An. gambiae and could be suitable for use in mosquito control programme for a Public Health purposes.