Larvicidal efficacy of ethanol leaf and seed extracts of Picralima nitida in the control of Culex quinquefasciatus and Aedes aegypti

Abstract

Picralima nitida is a medicinal plant used for the treatment of various ailments in southern Nigeria. This study aims at evaluating the prospects of using ethanolic extract of leaf and seed of Picralima nitida in the control of larvae of Culex quinquefasciatus and Aedes aegypti, Fourth instar larvae of test organisms were exposed in static bioassays to the crude extracts of P. nitida. Concentrations tested were 0.15-0.75 %w/v, at exposure periods of 24, 48 and 72 hours. At the end of assays (72 hr), the highest concentration (0.75 %w/v) of the ethanol leaf extract of P. nitida resulted in 48.00 and 50.40% mortality of larvae of Cu. quinquefasciatus and Ae. aegypti, respectively. At the same exposure period (72 hr) the ethanol seed extract (0.75 %w/v) resulted in larval mortality of 74.40 and 60.80% for Cu. quinquefasciatus and Ae. aegypti, respectively. The 72 hLC₅₀ values obtained from probit analysis revealed that larvae of Cu. quinquefasciatus were more susceptibe to the seed extract than larvae of Ae. aegypti, with 72hLC₅₀ values of 0.500 and 0.650%w/v, respectively. Phytochemical (qualitative) screening of the leaves and seeds of P. nitida detected the presence of alkaloids, cardiac glycosides, saponins and terpenes. In addition, flavonoids and tannins were detected in the seeds. This preliminary investigation has revealed that the leaves and seeds of P. intida have larvicidal potentials, and could be incorporated into the control measures for mosquito larvae.

Keywords: Picralima nitida, extracts, 72 hLC₅₀, Culex quinquefasciatus, Aedes aegypti