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.

One alpha-pyrone, obolactone (1), two chalcones, kurzichalcolactone B (2) and obochalcolactone (3), and two flavanones, oboflavanones A (4) and B (5), have been isolated from the fruits and the trunk bark of Cryptocarya obovata. The structures of the new compounds were elucidated by spectroscopic interpretations. The absolute configuration of obolactone (1) was established by circular dichroism. Obolactone (1) and obochalcolactone (3) display significant activity in in vitro cytotoxic assays against the KB cell line. Biosynthetic pathways for oboflavanones and obochalcolactone are suggested.