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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. • The molecular weight, compositions, rheological properties and molecular morphology of APs are different. • APs controlled prominently the levels of blood glucose, triglyceride (TG), total cholesterol (TC) Alanine transaminase (ALT) and blood urea nitrogen (BUN) in type 2 diabetic rats. • MAP and SCP showed positive effect in controlling the low density lipoprotein cholesterol (LDL-C) level of type 2 diabetic rats. • Oral administration of SCP significantly increased the high density lipoprotein cholesterol (HDL-C) level in type 2 diabetic rats. [ABSTRACT FROM AUTHOR]

Three algae polysaccharides (APs) extracted from Ascophyllum nodosum (ANP), Fucus vesiculosus (FVP) and Undaria Pinnatifida (USP) significantly differed in the zeta potential, water and oil holding capacity, monosaccharide composition, organic element composition, molecular weight distribution, microstructure and rheological properties. Antidiabetic effects of APs were compared by oral intervention at the dose of 400 mg/kg·body weight/day in high sugar and fat diets and streptozotocin injection induced type 2 diabetic rats. The analysis of body weight, water intake, fasting blood glucose, insulin, oral glucose tolerance, blood lipid indicators (including total cholesterol (TC), triglyceride (TG), low density lipoprotein cholesterol (LDL-C) and free fatty acid (FFA)), liver function indexes (involving alanine aminotransferase (ALT) and aspartate aminotransferase (AST)) and renal function profiles (comprising uric acid (UA) and urea nitrogen (BUN)) showed that APs possessed obvious antidiabetic activities, and FVP showed better effects in controlling the levels of FFA, AST, ALT, UA and BUN. Intervention of FVP reduced the total bile acid (TBA) level and elevated high density lipoprotein cholesterol (HDL-C) level of diabetic rats. Histomorphological observation further demonstrated that APs, especially FVP, could attenuate liver and kidney damage caused by diabetes. This study concluded that the antidiabetic effects of ANP, FVP and USP were distinctly different, which might be attributed to their different chemical structures. Therefore, the structure-activity relationship and antidiabetic mechanism of APs will be our future research direction. Unlabelled Image • The compositions, zeta potentials, molecular weights, rheological properties and microstructure of APs are significantly different. • USP has stronger water and oil holding capacity than ANP and FVP. • APs could ameliorate hyperglycemia, hyperlipidemia and liver and kidney damage of diabetic rats, and FVP shows better effects in controlling the levels of free fatty acid (FFA), alanine aminotransferase (ALT), aspartate aminotransferase (AST), total bile acid (TBA) and uric acid (UA). • Intervention of APs could decrease the serum insulin level of diabetic rats. • FVP could significantly increase the high density lipoprotein cholesterol (HDL-C) level of diabetic rats. • USP could more significantly reverse weight loss of diabetic rats than ANP and FVP. [ABSTRACT FROM AUTHOR]