Extraction,Sulfated Modification Of Kiwifruit Peel Pectin And Its Anticoagulant Activity

The Wuling Mountains is abundant in the kiwifruit resource,and kiwifruit peels are often generated in the deep processing of kiwifruit.The kiwifruit peels contain a high content of pectin,and the discard of the kiwifruit peel will not only seriously pollute the environment,but also cause a great waste of the resource.To develop and utilize the kiwifruit peel,which is a waste of kiwifruit deep processing,from the viewpoint of "sulfated polysaccharides often have anticoagulant activity",a hypothesis was made in this dissertation that "the sulfated pectin of kiwifruit peel may have anticoagulant activity".Taking kiwifruit peel as the research object,the optimization of the extraction conditions of kiwifruit peel pectin by ultrasonicmicrowave-assisted acid method,the sulfated modification of kiwifruit peel pectin,the anticoagulant activity determination of sulfated pectin of kiwifruit peel with different degrees of substitution,the separation and purification of high anticoagulant active components,and the structure identification of single anticoagulant active components were studied,in order to provide reference for green extraction technology of kiwifruit peel pectin and scientific theoretical basis for the development of sulfated pectin with anticoagulant activities.1.Optimization of process conditions for extracting kiwifruit peel pectin by ultrasonic-microwave-assisted acid method.The effects of p H,ultrasonic power,microwave power,extraction time,extraction temperature,and liquid-to-solid ratio on the yield of polysaccharide were investigated,and three factors that significantly affected the yield of polysaccharide were screened out by Plackett-Burman experiment:extraction temperature,extraction solution p H and microwave power,and their significance was in the following order: extraction temperature > extraction solution p H > microwave power.Through the Box-Behnken response surface experiment,the optimal process parameters of ultrasonic-microwave-assisted acid extraction of pectin from kiwifruit peel were determined as follows: p H 1.7 of extraction solution,extraction temperature of 91 °C,microwave power of 215 W,ultrasonic power of 250 W,extraction time of 35 min,liquid-material ratio of 30:1 m L/g.Under this process condition,the actual yield of pectin was 34.88%,which was very close to the predicted value of 35.23%,and the yield of polysaccharides was much higher than that obtained by the traditional hot water extraction method.2.Analysis of physicochemical properties of the kiwifruit peel pectin.The total sugar content of the kiwifruit peel pectin obtained by ultrasonic-microwave-assisted acid method was 60.83%,the degree of esterification was 54.53%,the content of galacturonic acid was 67.85%,the monosaccharide composition and its molar percentage were 4.2% of rhamnose,18.2% of arabinose,galactose 13.6%,glucose 5.5%,galacturonic acid 58.5%.Kiwifruit peel pectin contained 1.78% protein,but did not contain nucleic acids and polypeptides.Kiwifruit peel pectin was classified as highester pectin,and the molecule was dominated by RG-I domain.Kiwifruit peel pectin was a substance with uneven composition and rough surface,and it was composed of microsphere particles with compact structure.3.Sulfation modification of kiwifruit peel pectin and its anticoagulant activity.Four sulfated derivatives SKPP I,SKPP II,SKPP III and SKPP IV with degrees of substitution(DS)of 0.52,1.10,1.76 and 1.41 were prepared by changing the amount of sulfating reagent added.SKPP was protein and nucleic acid free.There existed a certain correlation between the degree of substitution and the infrared characteristic peaks.The four sulfated derivatives of kiwifruit peel pectin could prolong APTT time and TT time,and the anticoagulant activity increased with the increase of substitution degree.SKPP III had the highest anticoagulant activity among the four sulfated pectin derivatives.It was found that the sulfated derivatives of pectin exerted anticoagulant effects through the endogenous and common pathways.4.Separation and purification of components with high anticoagulant activity and preliminary structural analysis of single component with anticoagulant activity.SKPPⅢ was separated by DEAE-52 anion exchange chromatography and Sephadex G-100 gel chromatography,and SKPP Ⅲ-3a,a sulfated derivative of pectin with high anticoagulant activity,was screened out.Its APTT was up to 58.0 s,TT up to 20.3 s.The structure of SKPP III-3a was characterized,and the results showed that its molecular weight Mw was 19.6 k Da,and it was mainly composed of rhamnose,arabinose,galactose,glucose,and galacturonic acid,with a molar ratio of 7.2%,10.3%,24.2%,1.6% and 56.7%,respectively.Its microscopic morphology was flocculent and it had relatively smooth surface.