Bioactivity-guided isolation and purification of α-glucosidase inhibitor, 6-O-D-glycosides, from Tinta Cão grape pomace

• Tinto Cão grape pomace extract possesses potent α-glucosidase inhibitory activity.
• Flash chromatography and HPLC were developed to concentrate active α-glucosidase inhibitors.
• 6-O-D-glycosides was isolated from grape for the first time.
• 6-O-p-trans-coumaroyl-D-glucopyranosides are α-glucosidase inhibitors of grape pomace.

Bioactivity-guided fractionation methods were used to identify and purify active components in Tinta Cão grape pomace extract (GPE) that inhibit intestinal α-glucosidases. One active α-glucosidase inhibitor and one new natural product determined as 6-O-(p-coumaroyl)-D-glucopyranoside and methyl 6-O-(p-coumaroyl)-β-D-galactopyranoside, respectively, were isolated from GPE that were previously shown to potently inhibit α-glucosidase. Analysis of the relationship between structures and activity suggested that C1-OH of saccharide moiety in phenolic glycosides is necessary for this potent inhibition of intestinal α-glucosidases for the potential development of a novel anti-hyperglycaemic dietary supplement.