Norbergenin derivatives from Diospyros crassiflora (Ebenaceae)

From the ethyl acetate extract of the stems of Diospyros crassiflora Hiern, three new norbergenin derivatives, 4,11-di-O-galloylnorbergenin (1), 3-O-galloylnorbergenin (2), and 4-O-(4'-hydroxy-3'-methoxybenzoyl)-norbergenin (3), were isolated along with ten known compounds (4-13). Their structures were established by mean of spectroscopic techniques namely 1- and 2-D NMR experiments, mass spectrometry and comparison with reported data. Isolates 1-9 were evaluated for their ability to protect PC12 cells against hydrogen peroxide induced injury. Compounds with a galloyl group in their structure were found to prevent toxicity induced by H2O2 in PC12 cells.