Characterization and anti-diabetic evaluation of sulfated polysaccharide from Spirulina platensis

In this study, the structure, composition, cytotoxicity, and in vitro hypoglycemic activity of a polysaccharide isolated from Spirulina platensis (PSP1) and its degradation fragments (PSP2, PSP3) were assessed. Structurally, PSP was identified as a sulfated α-pyranose. All three tested polysaccharides were found to inhibit α-glucosidase, with the small-molecule polysaccharide PSP3 exhibiting the best efficacy in this context. MTT assays indicated that none of the tested polysaccharides exhibited cytotoxic activity when used to treat 3T3-L1 preadipocytes, whereas all three were able to enhance the glucose uptake capacity of these cells in a model of insulin resistance and PSP3 exhibited the best in vitro hypoglycemic activity. In vivo hypoglycemic activity of PSP3 indicated that its oral administration alleviated glucose and lipid metabolism disorders in STZ-induced diabetic mice, PSP3 alleviating insulin resistance in diabetic mice while also improving liver function parameters and antioxidant system activity.