AbstractThree xanthone derivatives, gambogic acid, isogambogic acid and isomorellinol, were isolated from the dried latex ofGarcinia hanburyi.Two of them, isogambogic acid and isomorellinol, are new. Determinations of the structures and stereochemistry were achieved independently by a series of NMR experiments including COSY, ROESY, HMQC, HMBC and selective INEPT. Isolation of isomorellinol fromG. hanburyiprovided important chemical evidence to link this species toG. morella.The presence of gambogic acid and isogambogic acid, however, demonstrated the difference between these two species. Cytotoxic evaluation of these isolates revealed that all three were active against KB and drug‐resistant KB‐V1 cell li