Soulaxanthone, a new xanthone derivative from Calophyllum soulattri .

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 1 H NMR, 13 C 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.