Three new xanthones from the bark of Garcinia dioica

Abstract

Three new xanthones were isolated from the bark of Garcinia dioica (Guttiferae) in addition to a known xanthone, 1,3,6-trihydroxy-8-geranyl-7- methoxyxanthone (rubraxanthone). The structures of the three xanthones were elucidated to be 1,3,6-trihydroxy-8-(7-hydroxy-3,7-dimethyl-2,5-octadieyl)- 7-methoxyxanthone, 1,3,6-trihydroxy-8-(6,7-epoxy-3,7-dimethyl-2-octenyl)-7- methoxyxanthone and 1,3,7-trihydroxy-2,4-diisoprenylxanthone by the aid of spectroscopic analysis including the two dimensional NMR technique. The occurrence of xanthone with such a C10 alkyl chain is rare in naturally occurring compounds.