New flavonoid C-O-C dimers and other chemical constituents from Garcinia brevipedicellata stem heartwood.

The methanol extract of the stem heartwood of Garcinia brevipedicellata has furnished three new flavonoid C-O-C dimers, brevipedicilones A (6), B (8) and C (10), along with five previously reported flavonoid dimers, viz. amentoflavone (1), 4.'-O-methylamentoflavone (2), robustaflavone (3), 4'-O-methyl robustaflavone (4) and tetrahinokiflavone (5). The new structures, which are composed of flavanone-flavanonol or flavanonol-flavanonol sub-units, were established based on spectroscopic analysis including 1D and 2D NMR (1H-1H COSY, HSQC, HMBC, and NOESY) spectroscopy, and by comparing their spectral data with those reported for related compounds.