| Apocynum venetum Linn is a kind of Apocynaceae Apocynum plant,which has strong adaptability and is widely distributed in the salt desert area of northern China,especially in the Yellow River Delta of our province.As a traditional Chinese medicine in China,Apocynum venetum has the functions of calming the liver,clearing away heat and promoting diuresis,etc.it is used to treat liver Yang vertigo,palpitation,insomnia,edema and oliguria.In China,we have produced the single prescription,compound tablet and Apocynum powder.In North America and Southeast Asian countries,Apocynum tea has been paid more attention because of its functions of lowering blood pressure,blood fat,blood sugar,sedation and hypnosis,and has been listed as a health product.There are many bioactive components in the leaves of Apocynum venetum.Many studies believe that the antihypertensive effect of Apocynum venetum is related to its flavonoids,but the active components of its hypoglycemic effect are not clear.In recent years,there are more and more studies on plant polysaccharides.A large number of studies have confirmed that plant polysaccharides have a wide range of pharmacological effects,such as improving immunity,scavenging free radicals,anti-tumor,anti infection,lowering blood lipid,lowering blood glucose and so on.At present,there are more studies on plant polysaccharides,especially on lowering blood glucose and blood lipid.Many studies in China believe that more than ten kinds of polysaccharide,such as Lycium barbarum polysaccharide,corn whisker polysaccharide and pumpkin polysaccharide,can reduce blood sugar and increase insulin level by gavage in diabetic animal models.However,the molecular weight of plant polysaccharides is large,the structure is complex,and the body lacks the corresponding digestive enzymes.This kind of polysaccharides can not be decomposed and absorbed,can not directly improve the function of islets of Langerhans,can not directly improve the metabolism and immune function of sugar in the body to achieve the effect of lowering blood sugar.Some studies have shown that the appropriate molecular can be obtained by using appropriate processing methods in the extraction process of plant polysaccharides The amount of polysaccharide,enhance its hypoglycemic and hypolipidemic effect.Therefore,this study intends to take different extraction methods for the polysaccharide of Apocynum venetum,compare its activity in vitro,verify its hypoglycemic effect in vivo,and provide scientific basis for the application of the polysaccharide in the field of medicine and health care.In this experiment,acid(HCl),alkali(NaOH)and distilled water were used to extract the polysaccharide of Apocynum venetum.The effects of different extractionsolvent and temperature on the yield of polysaccharide were studied.The chemical components of polysaccharides were determined by phenol sulfuric acid colorimetry,Bradford method,Folin phenol method and HPLC.The antioxidant activities of polysaccharides were determined by DPPH scavenging free radicals,ABTS scavenging free radicals and reducing ability.The in vitro bioactivity of polysaccharides was determined by the inhibition of ?-glucosidase and lipase.The polysaccharide was purified by 100% methanol washing,70% methanol washing,resin column chromatography and acid hydrolysis.Based on the biological activity in vitro,this experiment further studied the hypoglycemic and hypolipidemic effects of water extraction and alkali extraction of Apocynum venetum leaf polysaccharide on type II diabetic mice model.The model of type II diabetes was induced by high fat diet and STZ injection.The biochemical indexes and intestinal flora of mice in different groups were analyzed after 4 weeks of administration of Apocynum polysaccharide.The results showed that the yield of alkali extracted polysaccharide was the highest(21.32%),and its antioxidant activity and inhibition activity to ?-glucosidase and lipase were the strongest.However,there are a small amount of polyphenols and protein components in the Alkali extracted polysaccharide,and polyphenols have high antioxidant activity and enzyme inhibition activity.After purification,70% methanol washing and acid hydrolysis can effectively reduce the content of polyphenols and protein,and the scavenging ability of purified polysaccharide to DPPH radical is slightly reduced,and the scavenging ability and reducing ability to ABTS radical is significantly improved,especially after acid hydrolysis.In the aspect of enzyme inhibition activity,70% methanol washed polysaccharide had better inhibition activity to ?-glucosidase,but had no significant change to lipase,while acid hydrolyzed polysaccharide had no significant change to ?-glucosidase,but had a decrease to lipase.It is suggested that the inhibitory activity of ?-glucosidase mainly comes from the polysaccharide component,while the inhibitory activity of lipase is the result of the synergistic action of polysaccharide and polyphenol.The experimental results showed that compared with the diabetic mice,the fasting blood glucose,serum insulin,glycosylated serum protein levels,as well as the blood lipid profile including total cholesterol,triglyceride,low-density lipoprotein,cholesterol and free fatty acid in the intragastric administration of alkali treated mice were significantly improved.In addition,Alkali extracted polysaccharide could improve the antioxidant capacity and liver glycogen synthesis of diabetic mice.Both Alkali extracted polysaccharide and Water extracted polysaccharide could reverse the intestinal microflora disorder caused by type II diabetes.In conclusion,the polysaccharide extract of Apocynum venetum has high antioxidant activity and ?-glucosidase and lipase inhibitory activity.The polysaccharide of Apocynum venetum has obvious hypoglycemic effect on type II diabetic mice,and also hasregulating effect on intestinal flora of diabetic mice.This study will provide a new idea for the development of Apocynum polysaccharide as a functional nutrient for the treatment of type II diabetes. |
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