Bioactivity and characterisation of phytoconstituents from the stembark of Burkea africana Hook

O.K. Eboji, W. Cheng, B. Swanepoel, A.A. Sowemimo, M. Simelane, L. Venables, M. O. Sofidiya, M. van de Venter, T. Koekemoer, W. Lin

Abstract


Burkea africana Hook. (Caesalpinaceae) stem bark is used traditionally in West and Southern Africa for the treatment and management of tumors and cancer. Phytochemical investigation was done to determine the compounds responsible for cytotoxic activity of the plant. Bioactivity guided fractionation, chromatography and spectroscopic techniques were used to isolate and elucidate the compounds. Nine compounds were isolated from the stem bark of B. africana [stigmasterol and sitosterol (1), 1,3-dihydroxypropan-2-yl stearate (2), 2,3-dihydroxypropylstearate (3), catechin (4), epicatechin (5), 2α, 3α-epoxy-5,7,3’,4’-tetrahydroxyflavan–(4β→8)-epicatechin (6), epicatechin-(4β→8, 2β-O-7)-catechin (7), epicatechin (4β→8, 2β→O→7) ent-epicatechin (8) and epicatechin (4β →8, 2β →O →7)-epicatechin-(4α →8)-epicatechin) and epicatechin (4β→8, 2→O→7)-epicatechin (4β→8)-catechin) (9)].  Compounds 2, 3, 6-9 were isolated from B. africana stem bark for the first time.  Compound 9 exhibited moderate cytotoxic activity at 100 µM, while compounds 4-9 had excellent in vitro anti-oxidant activity. The compounds showed no significant capacity to attenuate nitric oxide production in LPS activated macrophages. This study authenticates the traditional use of B. africana stem bark in the treatment of cancer. 

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Chemical Society of Nigeria