Abstract

MELIACEAE PLANTS AND VECTOR CONTROL OF MALARIA: LARVICIDAL TOXICITY OF EXTRACTS AND FRACTIONS OF TRICHILIA MONADELPHA AND TRICHILIA EMETICA ON LARVAE OF ANOPHELES GAMBIAE

Umoh R. A.*, Ajaiyeoba E. O., Ogbole O., Fadare D. A., Johnny I. I. and Offor S. J.

Abstract

Introduction: Plants will continue to provide novel products as well as chemical models for new drugs in the coming centuries and may be used as sources of alternative agents for control of mosquitoes because of their rich bioactive chemicals. Aim: to evaluate the larvicidal toxicity of extracts and fractions of Trichilia monadelpha and Trichilia emetica on larvae of anopheles gambiae. Materials & Methods: The methanol extracts of the leaves and seeds of T. monadelpha and leaves of T. emetica of the Meliaceae family were subjected to toxicity studies on larvae of Anopheles grambiae, the malaria vector. The plant materials were extracted by maceration in 100% redistilled methanol for 72 hours and concentrated using a rotatory evaporator. The preliminary phytochemcial screening was done using standard methods. Larval toxicity of crude methanol extracts and fractions were evaluated by exposing fourth instar larvae of A. gambiae to varying concentrations (0.0625–10.0000 mg/mL). The larval mortality was recorded after 24 hours of exposure and LC50 values determined using the non-linear regression analysis of the graph pad prism® statistical package. The methanol crude extract of T. monadelpha leaves, seeds and T. emetica leaves exhibited % mortalities and had LC50 values of >1mg/mL, 0.11mg/mL and 0.22mg/mL respectively. Results: The hexane fractions of T. monadelpha leaves, seeds and T. emetica leaves were the most active of the fractions with LC50 values of 0.03mg/mL, 0.05mg/mL and 0.03mg/mL respectively. The reference compound N, N-diethyl-3-toluamide (DEET) had an LC50 value of 1.09 mg/mL. Preliminary phytochemical screening revealed the presence of tannins, saponins, cardiac glycosides, flavonoids, anthraquinones and terpenes. Conclusion: The results of the study suggest that the extracts and fractions of both Trichilia species are promising agents to be considered for development as vector control agents for malaria as the extracts and fractions had overwhelming activities compared to the reference compound.

Keywords: Anopheles gambiae larvae, Trichilia monadelpha, Trichilia emetica, larval toxicity.