Comprehensive structural analysis of polyphenols and their enzymatic inhibition activities and antioxidant capacity of black mulberry (Morus nigra L.)

In this paper, the structures of polyphenols and their bioactivity of black mulberry (Morus nigra L.) cv. 'Heisang No. 1' were comprehensively analyzed. The 11 anthocyanins and 20 non-anthocyanin phenolic compounds were identified and quantified by liquid chromatography high-resolution time-of-flight mass spectrometry (LC-HR-TOF/MS2). The cyanidin-3-glucoside and cyanidin-3-rutinoside were the major anthocyanins in the black mulberry. In addition, the black mulberry showed potent antioxidant capacity as assessed by DPPH, ABTS, and FRAP assays. Black mulberry anthocyanins exhibited stronger inhibition activities against α-amylase, α-glucosidase, and lipase compared to non-anthocyanin polyphenols, with IC50 values of 1.10, 4.36, and 9.18 mg/mL, respectively. The total anthocyanin content of black mulberry crude extracts and anthocyanins was 570.10 ± 77.09 and 1278.23 ± 117.60 mg C3GE/100 g DW, respectively. Black mulberry may be a rich source of polyphenols, natural antioxidants, and effective antidiabetic substances with great potential in the food industry.