Functional new acylated sophoroses and deglucosylated anthocyanins in a fermented red vinegar

The new acylated polyphenols were isolated from a red-colored vinegar produced via fermentation with purple-fleshed sweet potato storage roots, and identified mainly by MS and NMR. The three acylated sophoroses were determined as 6-O-(E)-caffeoyl-(2-O-(6-O-acyl)-β-D-glucopyranosyl)-D-glucopyranoses, where acyl was (E)-caffeoyl, p-hydroxybenzoyl, and (E)-feruloyl, respectively. The four acylated anthocyanins were also determined as cyanidin 3-O-(6-O-(E)-caffeoyl-(2-O-(6-O-(E)-feruloyl)β-D-glucopyranosyl) -β-D-glucopyranoside), in addition to peonidin 3-O-(6-O-(E)-caffeoyl-(2-O- (6-O-acyl)D-glucopyranosyl)-β-D-glucopyranosides), where acyl was (E)-caffeoyl, p-hydroxybenzoyl, and (£)-feruloyl, respectively. The diacylated sophoroses showed higher antioxidant capacity than that of monoacylated analogue 6-caffeoylsophorose, so the multiacylation established to enhance their antioxidant capacity. Similarly, 5-deglucosylated anthocyanins also gave somewhat stronger antioxidation than corresponding sweet potato anthocyanins. In rat intestinal α-glucosidase inhibition study, the diacylated sophoroses preferably inhibited maltase rather than sucrase with an IC₅₀ value of <300 μM, indicating a potential role as antidiabetic phytochemicals. These acylated polyphenols in a red vinegar were expected to play important functional roles for health.