Effects of extraction methods on physicochemical properties and hypoglycemic activities of polysaccharides from coarse green tea

Coarse tea is made of mature tea plant ( Camellia sinensis L.) shoots and is generally discarded as a worthless crop product, but has been proved an excellent material for the treatment of diabetes. This study aims to evaluate the effects of the extraction techniques WE (water extraction), UAE (ultrasound-assisted extraction), MAE (microwave-assisted extraction), and EE (enzyme extraction) on the physicochemical properties and antidiabetic activities of polysaccharides from coarse tea (CTPSs). The results showed that all four CTPSs had homogeneity in the monosaccharide types and similar IR (Infrared spectroscopy) characteristic absorption peaks, but differed in monosaccharide proportion and molecular weight distribution. Compared with the other three extraction techniques, CCTPS extracted by EE had the lowest protein content, the highest total sugar content of 71.83% and a polysaccharide yield of 4.52%. In addition, EE-CTPS had the best hypoglycemic activity that was better than ordinary green tea polysaccharides, the α-glucosidase and α-amylase inhibitory activities of EE-CTPS were highest in the range of 2–10 mg/mL compared with the other three CTPSs, which may be related to its smaller molecular weight and porous structure. The results suggested that the EE method was a good way to extract polysaccharides from coarse tea for food and pharmaceutical production.