Purification, Preliminary Structural Characterization, and In Vitro Inhibitory Effect on Digestive Enzymes by beta-Glucan from Qingke (Tibetan Hulless Barley)

Background and Objective. Qingke (Tibetan hulless barley, Hordeum vulgare L.) contains a high content of beta-glucan among all the cereal varieties. Although beta-glucan has multiple physiological functions, the physiological function of qingke beta-glucan was few studied. In this study, the beta-glucan was isolated, purified, determined the structural characterization, and measured the inhibitory activity to enzymes correlating blood sugar and lipid. Methods. beta-Glucan was isolated from enzymatic aqueous extract of qingke by using deproteinization, decolorization, DEAE-52 column chromatography, and sepharose CL-4B agarose gel column chromatography. The structure of the beta-glucan was determined using FT-IR and C-13-NMR spectra analysis, and molecular mass by use of HPSEC-dRI-LS. The kinematic viscosity was measured. The inhibitory effects of this beta-glucan on four enzymes were investigated. Results. This beta-glucan had a uniform molecular weight of 201,000 Da with beta-(1 -> 4) as the main chain and beta-(1 -> 3) as a side chain. The beta-glucan presented a relatively strong inhibitory activity on alpha-glucosidase, moderate inhibition on invertase, and a weak inhibition on alpha-amylase, whereas it did not inhibit lipase. Conclusion. The study indicates that the enzymatic beta-glucan from qingke has the potential as natural auxiliary hypoglycemic additives in functional medicine or foods.