Antioxidant Activities and Inhibitory Effects on Digestive Enzyme of Polyphenolic Extracts from Allium mongolicum Regel

The antioxidant capacities and digestive enzyme inhibitory effects of free and bound phenolic extracts from Allium mongolicum Regel were studied through antioxidant and enzyme inhibition assays in vitro. The methods of Folin-Ciocalteu, NaNO2-AlCl3 and vanillin-hydrochloric acid were used for the determination of total phenolics, flavonoids and condensed tannins, respectively. DPPH radical scavenging activity, ferric reducing antioxidant power(FRAP), trolox equivalent antioxidant capacity (TEAC) and inhibitory effects on HO· mediated 2-deoxyribose degradation assays were used to comprehensively evaluate the antioxidant capacity. In vitro digestive enzyme inhibitory test assay was used to evaluate the inhibitory effects of polyphenol extracts from A. mongolicum Regel on α-glucosidase and pancreatic lipase. The content of total phenol, flavone and condensed tannin of polyphenol extracts from A. mongolicum Regel were in the range of 251.09-521.27 μg GAE/mg, 148.24-512.94 μg CAE/mg and 121.33-360.56 μg CAE/mg, respectively, and their contents varied from different origins. The DPPH radical scavenging activity, FRAP and TEAC of free phenolic extracts from A. mongolicum Regel were in the range of 175.02-248.81 μmol TE/g, 646.22-842.89 μmol Fe(II)/g and 54.95-87.95 μmol TE/g, respectively. The DPPH radical scavenging activity, FRAP and TEAC of bound phenolic extracts from A. mongolicum Regel were in the range of 447.14-623.95 μmol TE/g, 1 051.78-1 866.22 μmol Fe(II)/g and 441.17-714.50 μmol TE/g, respectively. The IC50 values of free phenolic extracts for the inhibition of non-site and site hydroxyl radical-mediated 2-deoxyribose degradation ranged from 1.14 to 2.27 mg/mL and 3.39 to 3.70 mg/mL respectively. The IC50 values of bound phenolic extracts for the inhibition of non-site and site hydroxyl radical-mediated 2-deoxyribose degradation ranged from 0.62 to 0.94 mg/mL and 2.80 to 3.99 mg/mL, respectively. In general, the antioxidant capacity of the bound phenolic extract was stronger than that of free phenolics. The free and bound phenolic extracts inhibited the pancreatic lipase and glucosidase in a mixed non-competitive manner, and the inhibitory effect of free phenolics was stronger than of bound phenolics. In terms of the phenolic content, antioxidant capacity and digestive enzyme inhibition activity, the comprehensive quality of the bound phenolic extract was better than that of free phenolics. © 2024 Chinese Institute of Food Science and Technology. All rights reserved.