Inhibitory Effects of the Compounds Isolated from Sargassum yezoense on α-Glucosidase and Oxidative Stress

We examined ethanol extracts prepared from the Korean marine algae belonging to the Sargassaceae family for their inhibitory effects on α-glucosidase activity and free radicals in vitro. Among five marine algae, the extracts of Sargassum yezoense were found to possess strongly α-glucosidase inhibition and free radicals scavenging activities. Two compounds were isolated via bioactivity guided isolation and tested for their effects on α-glucosidase, DPPH, ABTS+ and Photochem∨_ analysis. Their chemical structures were elucidated by spectral analysis and direct comparison with authentic compounds; their structures were identified as sargaquinoic acid (1) and sargahydroquinoic acid (2). The inhibitory effects of compound 1 and 2 (IC∧50 value: 14.2 and 12.8 μM, respectively) on α-glucosidase were more potent that of deoxynojirimycin as a positive control (IC∧50 value: 18.0 μM). All compounds displayed antioxidative activity which was measured by DPPH, ABTS+ and Photochem∨_ apparatus.