Antimicrobial components of the methanolic extract from the stem bark of Garcinia smeathmannii Oliver (Clusiaceae)

The methanolic extract (GSM) prepared from the stem bark of Garcinia smeathmannii as well as ten compounds isolated from this crude extract, were tested for their antimicrobial activity against Gram-positive bacteria (6 species), Gram-negative bacteria (12 species) and 3 Candida species using well micro-dilution methods. The GSM showed very interesting inhibition effects on the growth of the tested pathogens with the minimal inhibition concentrations (MIC) lower than 156.25 μg/mL on 21 of the 22 pathogens tested. Purified compounds showed selective activities. Two of these compounds namely Cheffouxanthone (1) and Friedelin (9) exhibited both antibacterial and anticandidal activities. The antimicrobial activity of compounds 1, Bangangxanthone A (4), and Guttiferone I (7), as well as that of GSM is being reported for the first time. The overall results provide promising baseline information for the potential use of the crude extract from the stem bark of G. smeathmannii as well as some of the isolated compounds in the treatment of bacterial and fungal infections.