Isolation and Elucidation of Three Triterpenoids and Its Antimycobacterial Activty of Terminalia Avicennioides

Terminalia avicennioides Guill. & Perr. (Combretaceae) has been traditionally used as traditional medicine for centuries in Nupeland, North Central Nigeria for the treatment of respiratory diseases such as tuberculosis and cough. This study evaluates the in vitro antimycobacterial activities of the isolated compounds in order to support the therapeutic use of T. avicennioides for treating these infectious diseases. Chemical investigation by bioassay-guided fractionation led to the isolation of three triterpenoids namely, arjunolic acid (1), α-amyrin (2) and 2, 3, 23-trihydroxylolean-12-ene (3). Among them, arjunolic acid manifested the most potent antimycobacterial activity against a strain of Mycobacterium bovis (BCG). Structure elucidation of the isolated compounds were based primarily on the analysis of 1-D and 2-D NMR spectral data including HMQC, HMBC, COSY and NOESY correlations, as well as comparison with reported authentic data of arjunolic acid, α-amyrin and 2, 3, 23-trihydroxylolean-12-ene. To the best of our knowledge, this is the first time these compounds (1-3) are reported from this plant. The present result further confirms the value of ethnopharmacological investigations into traditional herbs for leads for potential drug development.