International Journal of TROPICAL DISEASE & Health

The quest for alternatives to synthetic chemical insecticides against mosquito vectors has necessitated studies on natural plant products. The larvicidal effect of ethanolic and aqueous extracts of a medicinal plant Sacoglottis gabonnensis stem bark were tested against 4^th instar larvae of Culex quinquefasciatus and Aedes aegypti. Larval bioassays were carried out at different concentrations (0.45 – 0.75% w/v) of the extracts in accordance with the WHO standard protocol. Mortality was recorded after 24 and 48 exposure hours. The LC₅₀ and LC₉₀­ were also determined. The highest concentration (0.75% w/v) of the ethanolic extract of S. gabonnensis resulted in 80% mortality of Cu. quinquefasciatus with LC₅₀ (2.59) and LC₉₀­ (3.42) and 70% mortality of Ae. aegypti with LC₅₀ (1.22) and LC_90­­ (2.31). At a concentration of 0.75% w/v the aqueous extract of S. gabonennensis resulted in 65% mortality of Cu. quinquefasciatus with LC₅₀ (2.84) and LC₉₀­ (3.62) and 60% mortality of Ae. aegypti with LC₅₀ (2.16) and LC_90­ (2.70). Cu. quinquefasciatus was not significantly (X²=1.66, df 1, P>0.05) more susceptible to ethanolic extract of the plant than Ae. aegypti. The susceptibility of both mosquito species to the aqueous extract was also not significant (X²=2.20, df 1, P>0.05). This preliminary investigation has revealed that the stem bark of S. gabonnensis could be harnessed in the formulation of potent biocides against mosquito vector.