In search for new metabolites from the stem bark of Calophyllum soulattri and Calophyllum gracilentum, led to the isolation of a new xanthone, soulaxanthone (1), along with four other known metabolites, euxanthone (2), calopolyanolide E (3), calanolide E (4) and friedelin (5). The structures of these compounds were identified and elucidated using spectroscopic techniques such as 1H NMR,13C NMR, COSY, DEPT, HSQC, HMBC, MS and FTIR. The antibacterial activities of compounds 1-5, as well as the extracts, were tested against five bacterial strains. Soulaxanthone (1) exhibited moderate activity against Pseudomonas aeruginosa with an MIC value of 25 µg/mL. Hexane (non-polar) extract from both plants exhibited moderate activity against Enterobacter cloacae (MIC = 250 µg/mL). Calopolyanolide E (3) and friedelin (5) showed bactericidal activity against Enterobacter cloacae (MBC = 50 µg/mL), thus the compounds have the potential to serve as a new lead for developing effective antibacterial medication.
Keywords: Calophyllum gracilentum; Calophyllum soulattri; antibacterial; soulaxanthone; xanthone.