Preparation Of Sulfated Barley Polysaccharide And Its Functional Properties

Barley (Hordeum vulgare), gramineae plant, is the world’s fourth largest category of cereal crops, mainly used as animal fodder and beer brewing material. Barley contains active ingredients such as polysaccharides, possessing many kinds of biological activity, for example, anti-oxidation, lowering blood glucose and serum cholesterol, immunity and anti-tumor. In this paper, barley was subjected to extraction of polysaccharide, modification of barley polysaccharide with sulfamic acid, and comparison of antioxidant activity and inhibition on α-glucosidase of sulfated barley polysaccharide and barley polysaccharide in vitro.(1) Extraction optimization of barley polysaccharide. Three extraction procedures were investigated:hot water extraction, microwave assisted extraction and ultrasonic assisted extraction. Factorial tests showed that for hot water extraction, the optical conditions were solid-to-liquid ratio1:20(g/ml), temperature80℃, time4h with an extraction yield of4.87%; for microwave-assisted, power400W, solid-to-liquid ratio1:30(g/ml), and time4min with an extraction yield6.24%; for ultrasonic assisted extraction, temperature75℃, power270W, solid-to-liquid ratio1:25(g/ml), and time8min with an extraction yield was6.69%.(2) Barley polysaccharide was modified with sulfamic acid. The degree of substitution (DS) was investigated as influenced by esterification reaction time, temperature, and sulfamic acid and formamide amount. Response surface methodology was applied to optimize the variables, and at the optimum conditions:temperature80℃, time5h, sulfamic acid dose1.5g, formamide dose50ml, the DS1.30was reached. Infrared spectrometry showed that sulfate groups had been linked to barley polysaccharide molecules after sulfation modification.(3) The antioxidant abilities of sulfated barley polysaccharide and barley polysaccharide were evaluated with total reducing power and scavenging effect of DPPH, hydroxyl radicals, superoxide anion radicals and lipid antioxidant. The results showed that for sulfated barley polysaccharide and barley polysaccharide respectively, the total reducing power was0.77and0.22Vc mg/ml; the scavenging activity to DPPH was62.39%and38.78%; the scavenging activity to OH was95.38%and58.38%; the scavenging activity to O2-was51.29%and33.25%. And sulfated barley polysaccharide and barley polysaccharide showed antioxidant properties on lard.(4) The sulfated barley polysaccharide and barley polysaccharide both could inhibit α-glucosidase, and inhibition increased with the concentration and DS. Barley polysaccharide biological activity was significantly enhanced after sulfated modification. The kinetic analysis showed that the inhibitory effects of sulfated barley polysaccharide and barley polysaccharide on α-glucosidase were reversible and sulfated barley polysaccharide was a mixed type while barley polysaccharide was a noncompetitive inhibiton.