Corchorusides A and B, new flavonol glycosides as α-glucosidase inhibitors from the leaves of Corchorus olitorius

Corchorus olitorius, a highly fibrous vegetable commonly known as moroheiya, has long been recognized for its hypoglycemic activity. Bioassay-guided fractionation of the leaf extract led to the isolation of two new flavonol glycosides named corchorusides A and B, in addition to a major component, capsugenin-25,30-O-β-diglucopyranoside. Corchoruside A comprises a kaempferol moiety connected with caffeic acid, glucose, and a rare methyl glucuronate (MeGlcA). The occurrence of a caffeoyl moiety in corchoruside A enhanced significantly its inhibitory effect toward α-glucosidase compared to that in corchoruside B.