Diverse polyphenol components contribute to antioxidant activity and hypoglycemic potential of mulberry varieties

Profiles of phenolic compounds, antioxidant activities, α-glucosidase inhibitory and anti-glycation activities of nine mulberry varieties were investigated. Twenty-three phenolic components were identified in the mulberry fruit. Chlorogenic was the predominant phenolic acid, while rutin was the most abundant flavonoid. In the colored mulberry fruits, the major anthocyanins were cyanidin-3-O-glucoside and cyanidin-3-O-rutinoside. Furthermore, we provide the first report of taxifolin-O-glucoside and two p-coumaroyl-caffeoylquinic acid isomers from mulberry fruit. The total phenolic content (TPC) ranged from 4.12 to 35.50 mg gallic acid equivalents (GAE)/g, while the total flavonoid content (TFC) varied between 1.16 and 39.95 mg rutin equivalents (RE)/g. The total anthocyanin content (TAC) ranged from 7.44 to 25.84 mg/g. The Zisang NO 1 variety presented the highest TPC, TFC and TAC with values of 35.50 mg GAE/g, 39.35 mg RE/g and 25.84 mg/g, respectively. Accordingly, it was characterized by the highest antioxidant capacity with values of 238.3 μmol Trolox equivalents (TE)/g and 560.1 μmol TE/g for DPPH and FRAP assays, respectively. Additionally, Zisang NO 1 showed better α-glucosidase inhibitory activity and anti-glycosylation activity, which may be due to its diverse polyphenolic composition. The antioxidant activity and the hypoglycemic potential were significantly higher in the colored mulberry fruits compared to the white mulberry varieties.