Physicochemical characterization and in vitro hypoglycemic activities of polysaccharides from Sargassum pallidum by microwave-assisted aqueous two-phase extraction

Microwave-assisted aqueous two-phase extraction (MAATPE) was applied for simultaneous extraction and separation of polysaccharides from Sargassum pallidum (SPPs). The optimal extraction parameters, physicochemical properties, and hypoglycemic activities in vitro of SPPs were investigated. The results revealed that the optimal extraction conditions were as follows: 21.0% ethanol (w/w) and 22.0% ammonium sulfate (w/w) for ATPS, ratio of material to liquid 1:60 (g/mL), extraction time 15 min, microwave power 830 W, and extraction temperature 95 °C. Under the optimal these conditions, the maximum yields of SPPs were 0.75 ± 0.04% of the top phase (SPP-1) and 6.81 ± 0.33% of the bottom phase (SPP-2). SPP-1 and SPP-2 were homogeneous with molecular weights of 1518.6 and 50.6 kDa, respectively. SPP-1 mainly consisted of fucose, galactose, mannose, and glucuronic acid with a molar ratio of 4.97:9.75:6.44:6.07, whereas SPP-2 was mainly composed of fucose, galactose, glucose, and mannose with a molar ratio of 4.20:2.88:18.05:7.83. SPP-1 and SPP-2 exhibited favorable α-amylase and α-glucosidase inhibitory activities, and could remarkably improve glucose consumption in insulin resistance (IR) model cells. Notably, SPP-1 exhibited stronger α-glucosidase inhibitory activity than SPP-2, and even was comparable with acarbose.