Study On Hypoglycemic Effect And The Mechanism Of HuiDouBa Polysaccharides

Huidouba(HDB) is processed from the cobweb that secreted by parasitic spider on the tea bushes on Emei Mountain in Sichuan province of China; it’s an effective Chinese traditional herb to treat the diabetes in local. Studies proved that polysaccharides in Huidouba are the main antidiabetic active constituent, but the present research on Huidouba polysaccharides mostly concentrated on crude polysaccharides and preliminary tests by animal experiments, the structure-activity relationship of Huidouba polysaccharides is rare, and the hypoglycemic effects and the mechanism on the molecular level are under exploration. So this article used Huidouba as raw material, focused on structure characterization, antioxidant activity and α-glucosidase inhibitory activity of Huidouba polysaccharides, and determined the hypoglycemic effect and the mechanism of Huidouba polysaccharides.1. Ultrafiltration technology was applied to further purification and fractionation of HDBP to obtain HDBP-1 and HDBP-2 with different molecular weigh. UV spectra analysis showed that HDBP-1 and HDBP-2 have no characteristic absorption peaks at 260 nm and 280 nm, indicated that HDBP, HDBP-1, and HDBP-2 are carbohydrate compounds, contain no protein or nucleic acid. IR spectra analysis showed the existence of α-configuration of the sugar units in HDBP-1 and β-configuration of the sugar units in HDBP-2. By means of GPC, HDBP-1 and HDBP-2 showed multiple peaks, and the average molecular weight was 36571 Da and 6277 Da respectively.2. The antioxidant abilities of HDBP, HDBP-1 and HDBP-2 were evaluated by scavenging effect of DPPH, ABTS and superoxide anion radicals and chelating ferrous ion ability. The results showed that HDBP, HDBP-1 and HDBP-2 have outstanding performance in scavenging activity to DPPH, ABTS and superoxide anion radicals and chelating ferrous ion ability, with a dose-effect relation existed. The antioxidant activity was related to the size of its relative molecular weight, and the small molecular weight polysacchsride HDBP-2 exhibited best antioxidant activity among HDBP, HDBP-1 and HDBP-2. The order of antioxidant capacity was HDBP-2 > HDBP > HDBP-1.3. HDBP, HDBP-1 and HDBP-2 showed prominent α-glucosidase inhibitory ability with the IC50 values of 0.019 mg/mL, 0.039 mg/mL and 0.013 mg/mL respectively, more potent than positive control acarbose(IC50 = 0.097 mg/mL). It was interesting to note that HDBP-2 showed the strongest α-glucosidase inhibitory effect among HDBP, HDBP-1 and HDBP-2, indicated that the α-glucosidase inhibitory was related to the size of its relative molecular weight. The order of inhibitory ability on α-glucosidase was HDBP-2 > HDBP > HDBP-1. The kinetic analysis showed HDBP and HDBP-2 inhibited α-glucosidase in a competitive pattern; however HDBP-1 inhibited α-glucosidase in a non-competitive pattern. The intrinsic fluorescence of α-glucosidase was quenched by Huioudba polysaccharides, which was caused by their combination, and the fluorescence quenching enhanced with the increase of Huidouba polysaccharides.4. The spontaneously type II diabetes KKAy mice was conducted to simulate human diabetes in order to study the effects of HDBP, HDBP-1 and HDBP-2 on the glycometabolism and lipid metabolism, and explore its hypoglycemic mechanism. The results showed that HDBP, HDBP-1 and HDBP-2 play an active role in reversing symptoms of diabetes in mice, it can decrease body weight, FBG, TC, TG, LDL concentrations and significantly enhance OGTT, indicating that Huidouba polysaccharides could suppress the obesity phenomenon and alleviate insulin resistance. Morphology observation shows that HDBP, HDBP-1 and HDBP-2 possessed significantly protective effects in the integrity of the organizational structure of the liver and pancreas.The above results suggested that HDBP, HDBP-1 and HDBP-2 may delay gastrointestinal digestion and absorption of carbohydrates and increase satiety by acting as α-glucosidase inhibitors, consequently reduce food ration and ameliorate insulin resistance, glycol metabolism and the disturbance of lipid metabolism. Meanwhile HDBP, HDBP-1 and HDBP-2 possess strong antioxidant ability; it can scavenge the free radical, protect the pancreatic function and improve insulin resistance, alleviate liver damages and improve lipid metabolism disorders.