Effects of different extraction methods on the structural properties and bioactivities of polysaccharides extracted from Qingke (Tibetan hulless barley)

In this study, four extraction methods, including ultrasonic assisted extraction (UAE), hot water extraction (HWE), microwave assisted extraction (MAE), and pressurized water extraction (PWE), were used to extract Qingke polysaccharides (THBs), and their physicochemical structures, in vitro antioxidant activities, and in vitro hypolipidemic activities were investigated and compared. Results demonstrated that the yields, the chemical compositions, the apparent viscosities, the molecular weights, and the molar ratios of constituent monosaccharides of THBs varied by different extraction methods. THB-P extracted by PWE possessed the highest molecular weight and apparent viscosity among all tested THBs. In addition, all THBs extracted by different methods exerted obvious in vitro antioxidant activities, in vitro binding capacities, and inhibitory effects on the pancreatic lipase. Indeed, both antioxidant activities and hypolipidemic activities of THB-P were higher than that of THB-H, THB-U, and THB-M obtained by HWE, UAE, and MAE, respectively, which might be due to the high molecular weight and apparent viscosity of THB-P. The findings indicated that the pressurized water extraction could be a convenient method for the extraction of polysaccharides from Qingke with high biological activities for applications in the functional food fields.