Microwave-assisted aqueous two-phase extraction of polysaccharides from Hippophae rhamnoide L.: Modeling, characterization and hypoglycemic activity.

Natural polysaccharides are concerned for their high biological activity and low toxicity. Two kinds of polysaccharides were extracted from Hippophae rhamnoide L. by microwave-assisted aqueous two-phase system. Under the optimal conditions predicted by RSM model (K 2 HPO 4 /ethanol (18.93 %/28.29 %), liquid to material ratio 77 mL/g, power 625 W and temperature 61 °C), the yield of total polysaccharides reached 35.91 ± 0.76 %. Moreover, the polysaccharides extraction was well fitted to the Weibull model. After purification by Sepharose-6B, the polysaccharides from top phase (PHTP, purity of 81.44 ± 1.25 %) and bottom phase (PHBP, purity of 88.85 ± 1.40 %) were obtained. GC, FT-IR, methylation and NMR analyses confirmed the backbone of PHTP was composed of a repeated unit →4)- β -D-Glc p -(1 → 2)- α -L-Rha p -(1 → 4)- β -D-Gal p -(1 → 4)- α -D-GalA p -(1 → 3)- α -L-Ara f -(1 → 3)- α -D-Man p -(1→, while the repeated unit in PHBP was →3)- α -L-Ara f -(1 → 2)- α -L-Rha p -(1 → 4)- β -D-Glc p -(1 → 3)- α -D-Man p -(1 → 4)- β -D-Gal p -(1 → 4)- α -D-GalA p -(1→. Compared with PHTP (6.46 × 106 g/mol), PHBP with relatively low molecular weight (8.2 × 105 g/mol) exhibited the smaller particle size, better water-solubility, thermal and rheological property, stronger anti-glycosylation and α -amylase inhibitory effects. Moreover, PHTP and PHBP displayed a reversible inhibition on α -amylase in a competitive manner. This study provides a high-efficient and eco-friendly method for polysaccharides extraction, and lays a foundation for sea buckthorn polysaccharides as potential therapeutic agents in preventing and ameliorating diabetes. [Display omitted] • MA-ATPE of two polysaccharides from sea buckthorn fruits was optimized by RSM model. • There were different repeated units in the backbone structures of PHTP and PHBP. • PHBP exhibited better physical and thermal stability, rheological property than PHTP. • PHTP and PHBP were novel natural agents for preventing and ameliorating diabetes. [ABSTRACT FROM AUTHOR]