Study On α-glucosidase Inhibitory Active Components From The Flower Of Apios Americana Mcdikus

Apios americana Medikus is a healthy food which can prevent hypertension and hyperlipemia as wellas cut down the risk of cancer and savenging free radicals. Most of today’s researches all focused on theunderground roots (tubers). In fact, the Japanese people were used to drink the Apios americanaMedikus scented tea to stabilized blood glucose and blood lipids. But studies on its hypoglycemic activepart, mechanism and effective ingredients have rarely reported. α-Glucosidase inhibitor is an effectivehypoglycemic agent, because it can prevent the hydrolysis of polysaccharides into monosaccharide, andthereby reduce postprandial hyperglycemia. This study preliminary explored the method for screeningthe active substances in the flower of Apios americana Medikus which have inhibitory activity onα-glucosidase, and established an α-glucosidase inhibition model in vitro. The components of two crudeextractions of Apios americana Medikus’s flower were analyzed, and the activities between the twoextractions were compared, then selected the one which have a better α-glucosidase inhibition toseparate and purificate preliminarily. The main contents of this paper are as follows:Using two methods-water bath reflux and ethanol immersion extraction-to extract the activecomponents in Apios americana Medikus’s flower, then detected their α-glucosidase inhibitory andantioxidant acitivies respectively. The ethanol extract have better inhibitory activity on α-glucosidasecompared with water extract, the IC50value of the former is2.04mg/mL, and the latter is5.64mg/mL,while antioxidant activity is of the opposite. Separate the aqueous solution of ethanol extract that havebetter inhibitory activity on α-glucosidase using organic solvent extraction method. Thus obtained fourpolar fractions, they were petroleum ether, n-butanol, ethyl acetate and water fractions, compared theirantioxidant activity and α-glucosidase inhibitory activity again. The ethyl acetate part has a highestcontent of saponins, about29.04%(on basis of extract), and showed a good antioxidant activity andstrong inhibitory activity on α-glucosidase, whose IC50values of DPPH and ABTS, FRAP value and theIC50value of α-glucosidase are77.54μg/mL,14.42μg/mL,6676.28μmol/L and137.12μg/mL,respectively. In which, the saponins have the highest activity. Eight phenolic compounds（p-coumaricacid, homovitexin, vitexin, isoorientin, orientin, caffeic acid, chlorogenic acid and tricin）were analyzedby HPLC for ethyl actate part. Among them, four compounds-vitexin, homovitexin, chlorogenic acid and caffeic acid were discovered in it, and their content were0.5234,0.0212,0.0045and0.0185mg/gsuccessively.Optimizing the extract process of total saponins in Apios americana Medikus’s flower usingResponse Surface Method. Based on single factor tests, effects of liquid-solid ratio, extraction time andethanol concentration on the content of total saponins were investigated. By box-behnken experimentaldesign with three factors and three levels, and established corresponding regression model, the optimumextraction parameters were as follows: liquid-solid ratio of20:1, extraction time of2h, and ethanolconcentration of90%. The total saponins content was7.18%under this condition, which is consistentwith predicted value roughly. To get the total saponins which have a higher content in Apios americanaMedikus’s flower, macroporous resin was used to separate and purificate the ethyl acetate fraction. Inaddition, its activities were verified after purification. The optimum process parameters of Apiosamericana Medikus’s flower with macroporous resin were as follows: macroporous type of D101,sample concentration of2.0mg/mL, sample volum of60mL, absorption time of3h, desorption liquidvolume fraction of80%, desorption solution volume of100mL and desorption solution pH of7. Thetotal saponins of Apios americana Medikus’s flower prepared with this method have a content of69.26%, what’s more, its antioxidant activities and inhibitory activity on α-glucosidase havesignificantly improved relative to ethyl actate fraction.The active component of the Apios americana Medikus’s flower, which have a good inhitiory activityon α-glucosidase was screened in this paper, providing a scientific basis for the development ofhypoglycemic drugs or foods in the future.