alpha-Glucosidase inhibitors from Commelina communis.

A methanolic extract of Commelina communis showed potent inhibitory activity against alpha-glucosidase. One pyrrolidine alkaloid, 2,5-dihydroxymethyl-3,4-dihydroxypyrrolidine (DMDP, 1) and four piperidine alkaloids, 1-deoxymannojirimycin (2), 1-deoxynojirimycin (3), alpha-homonojirimycin (4) and 7-O-beta-D-glucopyranosyl alpha-homonojirimycin (5) were isolated by bioassay-directed fractionation and separation. These compounds have been identified for the first time from Commelina communis, supporting the pharmacological basis of this plant that has been used as a traditional herbal medicine for the treatment of diabetes.