Abstract
The co-occurrence of geraniin (2) and a novel ellagitannin, elaeocarpusin (1) in Geranium thunbergii has been demonstrated. In addition, enzymatic transformation of 1 into 2 has been achieved, leading to the evidence that dehydroascorbic acid (4) participates as a co-enzyme in the oxidative metabolism of the hexahydroxydiphenoyl group to the corresponding dehydro group. Furthermore, flavan-3-ol derivatives and gallotannins containing a glucose and a quinic acid core have been isolated, together with previously reported ellagitannins.
