Antimicrobial and Antitubercular Activities of Bioactive Triterpenes from Clerodendrum capitatum (Willd) leaves.

Abstract

Clerodendrum capitatum used locally in the treatment of cough and respiratory tract infection was investigated for antimicrobial and anti-tubercular activities. A lanostane type triterpene carboxylic acid (1) and a lupane type triterpenoid (2) were isolated from the ethyl acetate soluble fraction of the leaves of Clerodendrum capitatum. The structures of the compounds were elucidated based on analysis of their spectral data, including 1H, 13C and 2D NMR and by comparison of the data with those reported in the literature. Compound 1 inhibited the growth of Mycobacterium bovis (BCG) at a minimum inhibitory concentration (MIC) of 250 µg/mL. The compounds were also active against 9 out of 12 tested microorganisms including; Bacillus subtillis, Pseudomonas aeruginosa, Staphylococcus aureus, Candida albicans and two resistant strains (vancomycin resistant entrococci (VRE) and methicillin resistant Staphylococcus aureus (MRSA)). The zones of inhibition (ZI) ranged between 20 and 29 mm against the microorganisms. The minimum inhibitory concentration (MIC) was as low as 62.5 µg/mL against Shigella dysenteriae, MRSA, Staphylococcus aureus and Bacillus subtillis for 1 and against MRSA, Pseudomonas aeruginosa, VRE and Shigella dysenteriae for 2; while the minimum bactericidal/fungicidal concentration (MBC/MFC) was as low as 125 µg/mL against Shigella dysenteriae and MRSA for 1 and 2 respectively. The studies clearly show the potential of C. capitatum in the search for bioactive compounds from plants. Keywords: Clerodendrum capitatum, Mycobacterium bovis (BCG), triterpene, NMR