Characterization, antioxidant and hypoglycemic activities of an acid-extracted tea polysaccharide

Tea polysaccharides have gained great attention but acid-assisted extraction was scarcely studied. Herein, an acid-extracted tea polysaccharide TP-1 was isolated. TP-1 contained glucose and galactose in a molar ratio of 4.33:1.00, and the molecular weight was 9.47 × 103 Da. The backbone is comprised of 1,4-α-Glcp, 1,6-α-Glcp, and 1,4-β-Galp, with branches of 1,4,6-α-Glcp. Polysaccharide TP-1 could scavenge DPPH, hydroxyl, and superoxide radicals, with the IC50 value of 457.1, 516.5, and 620.1 µg/mL, respectively. Furthermore, it could inhibit α-glucosidase and α-amylase activities with the IC50 value of 394.3 and 90.1 µg/mL, respectively. Meanwhile, glucose uptake was also observed to be significantly increased in insulin-resistant 3T3-L1 cells by TP-1. The results demonstrated that TP-1 might be employed for the control of diabetes mellitus.