Bioactivity of Essential Oils of Laggera pterodonta and Laggera aurita against Larvae of Anopheles gambiae, Malaria Vector

Abstract

The role of plants as sources of biologically active entities cannot be overstated. Plants belonging to different families with mosquitocidal activity have been discovered in established ethnobotanical and laboratory-based studies. Biological control of mosquitoes using botanicals remains the safest and most environmentally sound alternative to chemical control. The essential oil of two Nigerian Laggera species, L. pterodonta and L. aurita, were investigated with regard to their ability to kill the fourth instar larvae of the malaria vector, Anopheles gambiae. The WHO protocol was adopted for the larvicidal bioassay. Three replicates comprising 20 larvae each were exposed to various concentrations of the essential oil. Larval mortality was observed after 24 and 48 h, respectively. The results show that mortality increased with an increase in concentration and period of exposure. The essential oil of L. pterodonta was found to be the most effective, with LC50 values of 418 and 404 mg/L after 24 and 48 h, respectively, while the essential oil of L. aurita recorded LC50 value of 688 and 642 mg/L after 24 and 48 h, respectively. The GC-MS results reveal that the essential oil of L. pterodonta comprises 50.83% of compounds that have been reported to have larvicidal activity while the essential oil of L. aurita comprises of 43.69% compounds with larvicidal activity. The better activity of L. pterodonta essential oil could be attributed to it having a higher percentage of compounds such as ɤ-terpinene and 4-carvomenthenol with larvicidal activity. The results suggest that the essential oil of the plants have the potential to be used as an eco-friendly approach for the control of mosquitoes.