Structural characterization of polysaccharides from three seaweed species and their hypoglycemic and hypolipidemic activities in type 2 diabetic rats

Three algal polysaccharides (APs) were acquired from Scagassum (SCP), Sargassum fusiforme(Harv.) Setch. (SFP) and Macrocystis pyrifera(L.)Ag. (MAP) by hot water extraction, and their structural characterization and antidiabetic activity were investigated in high fat diet and streptozotocin-induced type 2 diabetic rats. The results revealed that there were obvious differences in extraction yield, molecular weight, compositions of monosaccharide and organic element, molecular morphology, rheological properties and the contents of total sugar, protein, uronic acid and sulfate of SCP, MAP and SFP. SFP had the highest extraction yield, the contents of total sugar and uronic acid and the smallest molecular weight. Congo red assay indicated that all polysaccharides had no triple-helix structure. Oral administration of APs prominently restrained loss of weight and increase of water intake (P .05), and also significantly controlled the increase of levels of blood glucose, triglyceride (TG) and total cholesterol (TC) in diabetic rats (P 0 .05). Diabetic rats treated with SCP had the highest high density lipoprotein cholesterol (HDL-C) level (P .05), similar to those in normal group. MAP and SCP showed positive effect in improving the low density lipoprotein cholesterol (LDL-C) level of diabetic rats (P .05). Meanwhile, the increased ALT and BUN contents caused by the liver and kidney damages were markedly ameliorated in the diabetic rats with APs intervention (P .05). As a consequence, APs could be promising candidates as natural medicines and functional foods for the improvement of diabetes and its complications.