Alpha-glucosidase inhibitor from Bergenia ligulata.

Inhibitory compound of alpha-glucosidase activity, (+)-afzelechin (1), was isolated from rhizomes of Bergenia ligulata. The structure was identified by IR, EI-MS, (1)H and (13)C NMR spectroscopy. The ID(50) (50% inhibition dose) value of compound 1 was 0.13 mM. To investigate the structure-activity relationship, (+)-afzelechin tetraacetate (2), (+)-5,7,4'-trimethoxyafzelechin (3), (+)-tetramethoxyafzelechin (4), and (+)-3-acetyl-5,7,4'-trimethoxyafzelechin (5) as the derivatives of compound 1 were evaluated as well.