ANTIBACTERIAL ACTIVITY OF XANTHONES FROM GUTTIFERAEOUS PLANTS AGAINSTMETHICILLIN-RESISTANT STAPHYLOCOCCUS-AUREUS

Extracts of Garcinia mangostana (Guttiferae) showing inhibitory effect s against the growth of S. aureus NIHJ 209p were fractionated accordin g to guidance obtained from bioassay and some of the components with a ctivity against methicillin-resistant Staphylococcus aureus (MRSA) wer e characterized. One active isolate alpha-mangostin, a xanthone deriva tive, had a minimum inhibitory concentration (MIC) of 1.57-12.5 mu g m L(-1). Other related xanthones were also examined to determine their a nti-MRSA activity. Rubraxanthone, which was isolated from Garcinia dio ica and has a structure similar to that of alpha-mangostin, had the hi ghest activity against staphylococcal strains (MIC = 0.31-1.25 mu g mL (-1)), an activity which was greater than that of the antibiotic vanco mycin (3.13-6.25 mu g mL(-1)). The inhibitory effect against strains o f MRSA of two of the compounds when used in conjunction with other ant ibiotics was also studied. The anti-MRSA activity of alpha-mangostin w as clearly increased by the presence of vancomycin; this behaviour was not observed for rubraxanthone. The strong in-vitro antibacterial act ivity of xanthone derivatives against both methicillin-resistant and m ethicillin-sensitive Staphylococcus aureus suggests the compounds migh t find wide pharmaceutical use.