Screening α-glucosidase inhibitors from four edible brown seaweed extracts by ultra-filtration and molecular docking

Abstract This research aimed to screen potential α-glucosidase inhibitors (AGIs) from Sargassum pallidum, Ecklonia kurome, Hizikia fusiforme and Undaria pinnatifida Suringar. Acetone was the best solvent to extract polyphenolic compounds in brown seaweeds with high total phenolic content. After concentrating with AB-8 macroporous resin, the enriched EtOH extract of Hizikia fusiforme extracts (HFEE) had the highest total phenolic content with 60.2 mg GAE/g E. The enriched acetone extract of Sargassum pallidum (SPEA) indicated the best α-glucosidase inhibitory effect with IC50 value of 270.7 μg/mL. A total of 21 potential α-glucosidase inhibitors were separated from four brown seaweed extracts by ultrafiltration, and included 2 phenolic acids, 5 terpenes, 4 flavonoids, 5 fatty acids, 3 simple phenolic compound, 1 ester and 1 other compound. The main constituents were palmitic acid (0.40-1.21 mg/g), poricoic acid A (0.58-1.62 mg/g), n-hexacosyl caffeate-hexose (0.92-2.37 mg/g), quercetin-3-O-glucuronide (1.02 mg/g in SPEA) and 6- gingerol (1.06-1.87 mg/g). Molecular docking has showed that poricoic acid A and quercetin-3-O-glucuronide could bind the active sites of α-glucosidase and form 4 and 6 hydrogen bonds in ligand-enzyme complex, and then caused the inhibition activity on α-glucosidase. The results showed the significant potential of Sargassum pallidum to be explored as AGIs.