Study On The Purification,Structural Characterization And Anti-diabetic Activity Of Polysaccharide Extracted From Anoectochilus Roxburghii

Anoectochilus is a very precious and perennial herb and its polysaccharide has various biological activities,such as antioxidant,hypolipidemic,anti-tumor and so on.Anoectochilus has widely used in the treatment of a variety of chronic diseases as well,which is called ’king medicine’.Diabete is a group of chronic disease caused by insulin deficiency/resistance and characterized by persistent hyperglycemia.Currently,the chemotherapy for diabetes includes insulin injections and oral hypoglycemic agents.However,almost all commercial drugs have toxicity and side effects.Therefore,the development of safe and effective phytomedicines with anti-diabetic activity will provide new strategies for prevent and treatment of diabetes and its complications.In this study,six polysaccharides(ARPs,ARPs-1,ARPs-2 and AFPs,AFPs-1,AFPs-2)respectively extracted from the whole plant,root and leaf parts of Anoectochilus roxburghii and Anoectochilus formosanus were firstly characterized,and their anti-diabetic activity were evaluated in STZinduced diabetic mice.After selecting the crude polysaccharide with the highest anti-diabetic activity,the polysaccharide was purified by anion exchange and size exclusion chromatography,and the structural characteristics of purified polysaccharide were systematically investigated.Furthermore,its anti-diabetic activity was evaluated to reveal the structure-activity between the polysaccharide structure and activity.The main results are as follows:1.Six polysaccharides extracted from A.roxburghii and A.formosanus were mainly composed of arabinose,mannose,glucose and galactose,and didn’t contain uronic acid.Among them,the monosaccharide composition of ARPs-1 and AFPs-1 were similar,which were both rich in glucose(97.53%and 94.56%,respectively)and a small amount of xylose.The average Mw of the polysaccharides from A.roxburghii,ranging from 148.6 KDa to 619.9 KDa,were obviously higher than those of the polysaccharides from A formosanus,ranging from 22.2 KDa to 66.0 KDa,and the average Mw of polysaccharides in different parts was significantly different.In addition,the root and leaf polysaccharides of A.roxburghii and A.formosanus had obvious differences in their configurations,while the structure of whole plant polysaccharides and root polysaccharides were basically similar,and contained both a and β configuration.2.In animal experiment,the anti-diabetic activity of ARPs(300 mg/kg/d)was significantly higher than other polysaccharides,followed by AFPs.Moreover,root polysaccharides had better anti-diabetic activity than leaf polysaccharides and there was a synergistic effect between root and leaf,so the anti-diabetic activity of whole plant polysaccharides was superior to root polysaccharides and leaf polysaccharides.3.After the separation and purification of ARPs,pure polysaccharide(ARPs-p)was obtained.It was a heteropolysaccharide with a molecular weight of 97.2 kDa and consisted of 97.75%glucose,1.2%galactose,0.5%rhamnose,0.26%arabinose,0.23%xyloseand,0.06%mannose and trace amounts of galacturonic acid.Moreover,the backbone structure of ARPs-p was composed of →3)-β-D-Glcp-(1→with some branching points at O-6 linked to non-reducing end units or 6-O-linked Glcp units.4.After intragastric administration of ARPs-p,the blood glucose level of diabetic mice induced by STZ was significantly reduced,the weight,liver glycogen,insulin and antioxidant enzyme levels were significantly increased,and the liver lipid level was also obviously improved.Thereinto,the high dose ARPs-p(200 mg/kg/d)has the most prominent therapeutic and repair effects,followed by the middle dose(100 mg/kg/d),but there was no dose dependence.By adjusting the antioxidant activity in mice,ARPs-p protected the islet cells of diabetic mice from free radical damage and improved hyperglycemia,oxidative stress and dyslipidemia,and thus showed excellent antihyperglycemic,antioxidant and antihyperlipidemic activitie.