Polyphenolic profile as well as anti-oxidant and anti-diabetes effects of extracts from freeze-dried black raspberries

Black raspberries are widely consumed in diets because of their potential health benefits attributed to abundant phytochemicals with biological properties. Twenty polyphenolic profiles (5 anthocyanins and 15 phenolics) were identified by HPLC-MS/MS. 10 compounds (3 anthocyanins and 7 phenolics) were isolated and confirmed by NMR, and two were isolated from Rubus for the first time. Freeze-dried black raspberry powder extracts were purified by polyamide resin with different concentrations of ethanol elution. The 30%, 50%, and 70% fractions exhibited the highest total monomeric anthocyanin, phenolic and flavonoid content, respectively. Moreover, the 30% fraction and compound 8, 9, 11, 17 exhibited optimal antioxidant activity. In α-glycosidase assay, the 70% fraction and compound 16, 17 demonstrated the greatest inhibitory effect. In PTP1B assay, the 30% fraction and compound 9, 11, 16, 17 exhibited the highest inhibitory effect.