Study On The Preliminary Characterization And Antioxidant Activity Of The Degradation Products From Porphyra Haitanensis Polysaccharide

Porphyra haitanensis is a large red algae plant,mainly distributed in Zhejiang,Fujian and other coastal areas.Porphyra polysaccharide(PP)is an important component of Porphyra haitanensis with various activities,such as antioxidant,immune regulation and other biological activities.At present,the research on PP mainly focused on the optimization of extraction conditions,the determination of physical and chemical properties and the preliminary study on the activity,However,the research on the degradation,structure and structure-activity relationship of sulfated polysaccharides of Porphyra haitanensis is still unclear.In the presented study,PP was isolated from the Porphyra haitanensis using water-extraction and alcohol-precipitation method.Then,the purification,physicochemical properties,degradation,antioxidant activity and structure of PP were analyzed.It also laid a theoretical basis for further elaborating the structure-activity relationship of PP,and also provided scientific basis for the development and utilization of Porphyra haitanensis.The main results of this study are as follows:(1)Isolation,purification and determination of physicochemical properties of Porphyra haitanensis polysaccharidePP was isolated from the Porphyra haitanensis using water-extraction and alcohol-precipitation method combined with the deproteinization,dialysis and freeze drying craft.After separating and purificating of PP using DEAE cellulose column,five components were obtained including PP1,PP2,PP3,PP4,PP5.And then the physical and chemical properties of PP1?PP5 were measured.The results showed that the molecular weights of PP1-PP5 were greater than 500 kDa.The sugar content of PP2(84.24%)and PP3(75.60%)was higher than that of other components,and the protein content of PP4(9.01%)was higher than that of other components.and the monosaccharide composition are mainly galactose and 3,6-anhydrogalactose,in addition,the monosaccharide composition of PP2?PP4 also contains 6-O-Me-galactose,and the monosaccharide composition of PP5 also contains mannose and glucose.The sulfuric acid content of PP3(20.1%)was significantly higher than that of other components.Due to the content of sulfate group is closely related to the activities of polysaccharide,PP3 was used as the following study sample.(2)Study on the degradation of PP3 and antioxidant activities of its productsThe study used hydrogen peroxide-ascorbic acid system to degrade PP3.We measured the content of sugar,sulfuric acid and the antioxidant activity of the four degradation products,and the molecular weights of the four degradation products were 102 kDa,72 kDa,39 kDa and 20 kDa,respectively.The results showed the sugar content of PP3-1?PP3-4 were 78.0%;75.5%;75.1%;75.0%,and the sulfuric acid content were 18.9%;18.0%;17.2%;19.8%.After analyzing the antioxidant activity of PP3 and its four degradation products,it showed that the antioxidant activity of four degradation products have a positive relationship with its concentration.Among them,superoxide anion scavenging activities of PP3 and PP3-1?PP3-4 were listed in a descending order:PP3-4>(PP3-3/PP3-2/PP3-1)>PP3;hydroxyl radical scavenging activities were listed in a descending order:PP3-4>PP3-3>PP3-2>PP3-1>PP3;reducing powers were listed in a descending order:PP3-4>PP3-3>PP3-2>PP3-1>PP3;DPPH radical scavenging activities were listed in a descending order:PP3-4>PP3-2>PP3-3>PP3-1>PP3.(3)Purification of PP3-4 and structure characterization of PP3-4PP3-4 was purified by sephadex G-100 to obtain homogeneous component with the yield of 91%.The molecular weight of PP3-4 was 20 kDa after measuring from HPGPC.The cotent of 3,6-anhydro-galactose and galactose were 6%and 69%,respectively(molar ratio 1:10).The results showed that PP3-4 was composed of galactose,6-O-Me-galactose and 3,6-anhydro-galactose using the method of GC and GC-MS combined with the determination of 3,6-anhydro-galactose and galactose content.The structure of PP3-4 was analyzed using FT-IR and NMR.The results showed that the structure of PP3-4 was consistent with the typical red algae structure,including?3)?-D-galactose(1?4)3,6-anhydro-a-L-galactose(1?,and ?3)?-D-galactose(1?4)a-L-galactose-6-S(1?repeating disaccharide units,and the latter structure is dominating,and the C-6 of?-D-galactose and the C-2 of the 3,6-anhydro-galactose are partially replaced by the methoxy group.The glycosidic bond type of the anomeric proton includes both alpha and beta.