Carboxymethylation of Qingke β-glucans and their physicochemical properties and biological activities

In this study, the response surface methodology was used to optimize the reaction conditions of carboxymethylated modification of Qingke β-glucans (QG), and effects of different degrees of carboxymethylation (high, medium, and low) on their structural characteristics, in vitro antioxidant activities, and in vitro hypolipidemic activities were studied. The optimal reaction conditions of carboxymethylated Qingke β-glucans (QG-Cs) with high degree of carboxymethylation (DC = 0.90) were as follows: reaction temperature of 62.1 °C, reaction time of 3.29 h, and concentration of chloroacetic acid of 1.75 mol/L. Results demonstrated that the carboxymethylated modification significantly affected the solubilities, molar ratios of constituent monosaccharides, molecular weights, and apparent viscosities of QG. Indeed, the QG-Cs exhibited much higher antioxidant activities (reducing powers, NO, and DPPH radical scavenging activities), in vitro binding properties (fat, bile acid, and cholesterol binding capacities), and pancreatic lipase inhibition activities than that of QG. Furthermore, results showed that bioactivities of QG-Cs were closely correlated to their carboxymethyl groups. Results suggested that the carboxymethylated modification could be an efficient method for enhancing bioactivities of QG, and QG-Cs had good potential applications in bio-pharmaceutical industry.