Separation, Purification, Structural Characterization And Physiological Activity Of Polysaccharides From Opuntia Dillenii Haw. Fruits

In this paper, wild cactus fruit (O. dillenii Haw.) purchased from Sanya, Hainan province, was used as raw material, and the structure, physical and chemical properties and physiological activity of cactus fruit polysaccharides were studied.A new water-soluble polysaccharide fraction (ODFP) with molecular weight of 6479.1 kDa was isolated and purified from the peeled fruits of Opuntia dillenii Haw. by water extraction, alcohol precipitation, DEAE-52 cellulose and Sephadex G-100 column chromatography, which consisted of rhamnose, xylose, mannose and glucose in the molar ratio of 14.99:1.14:1.00:6.47, with polysaccharide content of 90%, uronic acid content of 19.82%. Combined with methylation analysis, Fourier transform infrared spectroscopy (FT-IR) and nuclear magnetic resonance spectroscopy (NMR), the specific structural features of ODFP were analyzed. ODFP were composed by â†'2)-a-L-Rhap-(1â†', β-D-Glcp-(1â†',â†'3,4)-β-D-Xylp-(1â†' and â†'6)-P-D-Manp-(1â†', P-D-Glcp-(1â†' was the extremity of the chain.This study made the physicochemical properties of ODFP clear and showed that ODFP has good thermal stability. Rheological results indicated that the viscosity of the cactus fruit increased as the concentration. Meanwhile, rheology property of ODFP was investigated by the addition of Ca2+, which can significantly increase the viscosity of ODFP aqueous solution.The aim of the in vivo experiment was to investigate the possible protective effect of cactus fruit polysaccharide (polysaccharide content≥80%) against oxidative damage in streptozotocin (STZ)-induced diabetic rats. The results showed that the oral administration of cactus fruit polysaccharide (200mg/(kg·d)) significantly decreased food intake, water intake, urine production, organ weights and fasting blood glucose level, and markedly increased body weight loss in STZ-induced diabetic rats. Cactus fruit polysaccharide also significantly increased the activities of antioxidant enzymes superoxide dismutase (SOD), glutathione peroxidase (GPx) and catalase (CAT), and decreased the level of malondialdehyde (MDA) in serum, liver, kidney, and pancreas in STZ-induced diabetic rats. Moreover, histopathological examination of pancreas showed that ODFP could markedly improve the structure integrity of pancreatic islet tissue in STZ-induced diabetic rats. This study suggested that cactus fruit polysaccharide had hypoglycemic and antioxidant properties and could protect rats from STZ-induced oxidative stress in a dose-dependent manner.The result from in vitro experiment found that:ODFP exihibited significant reducing power, metal ion chelating ability and scavenging ability for hydroxyl radicals, superoxide anion radical, DPPH radical, which indicating ODFP has good antioxidant activity.