Antioxidant and Anti-Tyrosinase Activities of Supernatants from Water Extracting-Alcohol Precipitation of Ishige okamurai and Hypoglycemic Effect of Its Granules

Abstract:

The study aimed to investigate the antioxidant，anti-tyrosinase，and hypoglycemic activities of the extracts from Ishige okamurai.The antioxidant activities of the supernatants from water extracting-alcohol precipitation of Ishige okamurai（hereafter，referred to as simply SWEAPI） were determined by the DPPH and hydroxyl radical scavenging system，its anti-tyrosinase activity was determined by the dopachrome method. Using SWEAPI as basic material and soluble starch，sodium cyclamate，and β-cyclodextrine as auxiliary materials，the granules were prepared by the optimization conditions from orthogonal experiment. The hypoglycemic effects of granules were studied by in vitro α-glycosidase enzyme activity inhibition experiment and in vivo alloxan-induced diabetic mice. The results show that EC50 of DPPH scavenging is 1.19 mg/mL，EC50 of hydroxyl radical scavenging is 5.08 mg/mL，and IC50 of tyrosinase inhibition is 1.27 mg/mL. These phenomena are related to its higher polyphenol content（8.30%）. When the granules are made by the optimization conditions with the 30∶60∶1∶7.5 ratio of SWEAPI：soluble starch：sodium cyclamate：β-cyclodextrine，it has the best product quality with content of water（≤10%），total sugar（18.74 %），protein（16.60%），and polyphenol（2.53%）. The granules have strong inhibitory activity against α-glycosidase enzyme with IC50 of 0.37 mg/mL. Compared with the model control group，the granules could significantly reduce the blood glucose level of diabetes mice after 14 days of treatment with oral dose of 350 mg/kg. The granules also could reduce postprandial blood glucose level in a short time by the results of glucose tolerance experiment，which are similar to positive drug metformin at dose of 500 mg/kg. In conclusion，SWEAPI has strong antioxidant，anti-tyrosinase，and hypoglycemic activities with potential applications in skin care products and hypoglycemic functional products.