Structural characterization and inhibition on α-glucosidase of a novel oligosaccharide from barley malt

The barley was used as material. The effects of germination time on the inhibition on α-glucosidase and saccharides properties of barley malt were explored. The inhibition on α-glucosidase of crude saccharides was the highest and the proportion of low molecular weight saccharides was the highest (86.72%) in 4 d. A novel oligosaccharide was separated from the crude saccharides of 4 d with column chromatography. The structure of the oligosaccharide was analyzed with HPLC, MALDI-TOF-MS, FT-IR, NMR. The oligosaccharide was α-pyran glucosan which composed of four glucoses with (1 → 3) linkage. And its specific optical rotation and molecular weight were +45° and 666 Da, respectively. The half maximal inhibitory concentrations (IC50) of crude oligosaccharide, pure oligosaccharide and acarbose were 1.30 mg/mL, 0.48 mg/mL and 0.26 mg/mL, respectively. All the results demonstrated that the pure oligosaccharide has in vitro inhibition on α-glucosidase. The achievement of this study not only developed a new oligosaccharide but only demonstrated the inhibition on α-glucosidase. It provided new orientation on development of barley and had significant importance to the utilization of barley.