Potential hypoglycemic activity of anthocyanidins monoglucoside and diglucoside from Yan 73 (Vitis vinifera L.) and spine grape (Vitis davidii Foex)—effect on α-glucosidases of gut microbiota and human Caco-2 cells

Malvidin-3-O-glucoside (mv-3-O-glc), malvidin-3,5-O-diglucoside (mv-3,5-O-diglc), and malvidin-3-O-(6-O-coumaroyl) -glucoside-5-O-glucoside (mv-3,5-O-diglcCoum) extracted from Yan 73 (Vitis vinifera L.) and spine grape (Vitis davidii Foex) were used to investigate the effect on maltase and sucrase in the gut microbiota and Caco-2 cells. The results showed that three anthocyanins exhibited the inhibition of both maltase and sucrase in Caco-2 cells, and mv-3,5-O-diglc was the most effective one with an IC₅₀ of 258.96 μM for maltase and 189 μM for sucrase, respectively, through a mixed-type inhibitory mechanism. The strong inhibition was also supported by the significant decrease in sucrase mRNA and protein levels in Caco-2 cells after treatment with mv-3,5-O-diglc for 4 h. Moreover, the inhibition effect of anthocyanins was observed only on maltase, which originated from the gut microbiota. The inhibition potential of mv-3-O-glc against maltase was higher than that of the other two anthocyanins in a mixed-type inhibition manner (IC₅₀ = 9.66 ± 0.33 μM). Molecular docking revealed that mv-3-O-glc and mv-3,5-O-diglc formed hydrogen bonds with the aspartic acid (ASP) 443 catalytic residue of maltase, respectively, and then inhibited the enzyme activity by occupying the catalytic center. In particular, mv-3,5-O-diglc could easily fit into the active center of sucrase and form hydrogen bonds with the ASP1394 residue, which could be another reason for the inhibition of sucrase. Thus, anthocyanins, especially the diglucoside anthocyanins derived from grapes, are good potential α-glucosidase inhibitors for regulating postprandial blood glucose levels as dietary supplements.