Norbergenin derivatives from the stem bark of Diospyros sanza-minika (Ebenaceae) and their radical scavenging activity

Abstract Three new norbergenin derivatives, 11- O - p -hydroxybenzoylnorbergenin, 4- O -(3′-methylgalloyl)norbergenin and 4- O -syringoylnorbergenin were isolated from the stem bark of Diospyros sanza-minika , along with three known compounds: norbergenin, 4- O -galloylnorbergenin and quercitol. Their structures were established on the basis of 1D and 2D NMR experiments and mass spectrometry. Some of the above compounds showed radical scavenging properties in a DPPH solution assay.