| Firstly, the contents of total carbohydrate, total nitrogen, soluble protein and uronic acid, intrinsic viscosities and the monosaccharide profiles of six polysaccharides including DHP, DOP, DFP, DCP, DNP and DMP, obtained by water extraction and ethanol sedimentation from the plants of Dendrobium huoshanense, D. officinale, D. fimbriatum, D. chrysotoxum, D. nobile and D. moniliforme, respectively, were analyzed. Then the effects of different doses of six Dendrobium polysaccharides on weight gain, liver index, biochemical indicators in serum and liver tissues, activities of antioxidant enzymes and alcohol metabolizing enzymes and the expression of cytokines by replicating the model of alcohol-induced liver injury in mice were evaluated.The results showed that the contents of total carbohydrate, total nitrogen, soluble protein and uronic acid of the six Dendrobium polysaccharides were in the range of74.27%-93.10%,1.60%-3.68%,0.15%～0.80%and3.92%-10.90%, respectively; and the highest contents of which were DOP, DHP, DFP, DNP and DFP, respectively; while the lowest contents of which were DNP, DCP, DCP, DMP and DHP, respectively. The intrinsic viscosities of the six Dendrobium polysaccharides were in the range of35.05～134.30cm3/g. DFP had the highest intrinsic viscosity and DHP had the lowest one. Monosaccharide analysis showed that all the polysaccharides were determined to be heteropolysaccharides containing mannose, galactose and glucose as major sugar and traces of other monosaccharide.The results of experiment on the intervention effects of Dendrobium polysaccharides on alcohol-induced liver injury in mice indicated that the levels of ALT, AST, ALP, TBIL, TC, TG and LDL-C in serum and TC, TG and MDA in liver tissues had significantly increased, while the levels of ADH, ALDH, SOD, CAT, GSH-Px, GR, GST and GSH in liver tissues, as well as HDL-C in serum, had significantly decreased in alcohol control group mice, when compared to the normal control group. The Dendrobium polysaccharides played an efficient role in the restoration of the alcohol-induced liver injury, which were evidenced by the following:①The disturbed levels of serum ALT, AST, ALP and TBIL in mice with alcohol-induced liver injury were restored towards normalization;②The activities of ADH and ALDH were increased, promoting the role of alcohol in vivo and decreasing deleterious effect of alcohol and its metabolites.③The levels of serum TC, TG, LDL-C, HDL-C, as well as hepatic TC and TG were also restored, correcting lipid metabolism disorders caused by alcohol in mice,④The activities of SOD, CAT, GSH-Px, GR and GST and the levels of MDA and GSH in liver tissues were restored, reducing lipid peroxidation, protecting the body’s antioxidant defense system, and inhibiting the occurrence of oxidative stress.⑤In addition, the expression of hepatic P4502E1mRNA was significantly inhibited by DHP, DOP and DFP, thereby reducing the generation of free radicals to avoid liver antioxidant defense system from damage; The expression of hepatic TNF-α and IL-1β mRNA were significantly inhibited by DHP and DOP, slightly by DFP and DCP and not obviously by DFP and DCP.In conclusion, there were some differences between physicochemical properties and hepatoprotective effects of the six Dendrobium polysaccharides, and their hepatoprotective effects on alcohol-induced liver injury mice decreased in the order of DHP>DOP≌DFP≌DCP≌DNP>DMP. The results obtained in this study would provide a general guideline for choosing elite varieties for Dendrobium cultivation and a reference for the rational use of Dendrobium polysaccharides in functional food processing. |
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