Antibacterial caged-tetraprenylated xanthones from the stem bark of Garcinia scortechinii

Five new caged-tetraprenylated xanthones, scortechinones L - P (1-5), together with six known scortechinones (A, B, D, F, I and J) and one known xanthone, 4 '',5 ''-dihydro-1,5-dihydroxy-6 ',6 '-dimethylpyrano(2 ',3 ':6,7)-4 '',4 '',5 ''-trimethylfurano(2 '',3 '':3,4)- xanthone, were isolated from the crude methanol extract of the stem bark of Garcinia scortechinii. The structures were elucidated by analysis of spectroscopic data and comparison of the NMR data with those reported previously. The antibacterial activity of all caged-polyprenylated xanthones, isolated from the latex and stem bark of G. scortechinii, was evaluated. Scortechinone B (6) exhibited significant antibacterial activity against a methicillin-resistant Staphylococcus aureus strain with an MIC value of 2 microg/mL. From the MIC values, some structure-antibacterial activity relationships were established.