The need for natural products from plant origin as possible alternatives to chemical insecticides prompt investigation on the larvicidal potential of the essential oil from the aerial shrub of Phyllanthus amarus Sch. et Thonn (Euphorbiaceae) against three species of mosquito vectors. Oil obtained from the plant using hydro distillation was analyzed for chemical constituents with GC and GC/MS. Bioassay on the larvicidal activity was performed using third instar mosquito larvae. The three mosquito species tested An. gambiae, Cx. fatigans and Ae. aegypti displayed sensitivity to the various concentrations at low LC50 and LC95 values of 0.1 and 0.02% (w/v) respectively. GC-MS displayed 82 compounds consisting mainly of oxygenated monoterpenoids (45.2%) and diterpenoids (14.9%). Other compound present in large amount is linalool (36.4%). The bioactivity of the oil on mosquito species tested may be due largely to the synergistic effect of other constituents therein.The results showed susceptibility of the larvae of the three mosquito species to the essential oil tested even at low concentrations, hence its potential use in the development of new agent with less toxic bioactive compounds from indigenous plant for malaria control.
