Effects of sulfated modification on the physicochemical properties and biological activities of β-glucans from Qingke (Tibetan hulless barley)

In this study, the reaction conditions of sulfur trioxide-pyridine (SO3-Pyr) method for the modification of Qingke β-glucans (THB) were optimized by response surface methodology, and effects of different degrees of substitution (low, medium, and high) on the physicochemical properties, antioxidant activities, and in vitro hypolipidemic activities of THB were investigated. The optimal reaction conditions to obtain the high degree of substitution of sulfated β-glucans were as follows: ratio of SO3-Pyr to THB of 16.88 g/g, reaction time of 2.03 h, and reaction temperature of 57.54 °C. Results showed that sulfated modification significantly affected the water solubilities, apparent viscosities, molecular weights, and molar ratios of constituent monosaccharides of THB. Besides, the sulfated THB exhibited much better antioxidant activities (DPPH and nitric oxide radical scavenging activities, and reducing powers), in vitro binding properties (fat, cholesterol, and bile-acid binding capacities), and pancreatic lipase inhibition activities than that of THB. Indeed, the sulfated THB with higher degree of substitution has stronger antioxidant activities and in vitro hypolipidemic activities. Results suggested that the sulfated modification could be an efficient approach for the improvement of functional properties of THB, and sulfated THB could be further explored as functional food ingredients for industrial applications.