Extraction, purification, hypoglycemic and antioxidant activities of red clover (Trifolium pratense L.) polysaccharides

Hot water extraction was applied to extract red clover (Trifolium pratense L.) polysaccharides (RCP) and the extraction conditions were optimized using the response surface methodology (RSM). An RCP yield of 12.72 ± 0.14% was achieved under the optimum extraction conditions: extracting time of 95 min, extracting temperature of 93 °C, and solvent-material ratio of 21 mL/g. A component named RCP-1.1 with the molecular weight of 7528.81 kDa was purified from RCP. RCP-1.1 was composed of glucose, galacturonic acid, arabinose, and galactose, with molar percentages of 52.54, 1.04, 16.31, and 30.11%, respectively. At the determination concentration of 10 mg/mL, the α-glucosidase inhibition ability of RCP-1.1 reached 86.72% of that of acarbose. The scavenging rates of RCP-1.1 (3.0 mg/mL) for DPPH and ABTS radicals reached 91.82% and 98.95% of that of ascorbic acid (3.0 mg/mL), respectively. Based on these results, RCP-1.1 possesses the potential to be used as a natural hypoglycemic agent or an antioxidant.