No abstract

Bioassay-guided fractionation of a leaf extract of G. bracteata has yielded six new prenylxanthones, bractatin (1), isobractatin (2), 1-O-methylbractatin (3), 1-O-methylisobractatin (4), 1-O-methyl-8-methoxy-8,8a-dihydrobractatin (5), and 1-O-methylneobractatin (6). The structures of these compounds have been elucidated by spectroscopic means (NMR, MS), literature data, and X-ray crystallographic analysis of 2. These compounds possess significant cytotoxicity against the KB cell line.

Microtubule disassembly inhibitory properties have been established for the known polyisoprenylated benzophenones xanthochymol (1a) and guttiferone E (1b). The compounds were isolated from the fruits of Garcinia pyrifera collected in Malaysia. A structure-activity relationship study, including natural and semisynthetic derivatives, delineated some structural features necessary for the interaction with tubulin within this compound class.