Study On Preparation And Activity Of Nymphaea Hybrid Polysaccharides With Different Molecular Weight

Nymphaea hybrid is a large water lily,belonging to the family of Nymphaea L,which has a large area of planting bases in many provinces of China.Nymphaea hybrid is rich in polysaccharides,however,there are few reports on the extraction,physicochemical properties and biological activity of polysaccharides from Nymphaea hybrid.Therefore,the effects of three different extraction methods on the physicochemical properties,structure and activity of Nymphaea hybrid polysaccharides were studied.The method of ultrasound-assisted extraction was selected for the preparation of high active polysaccharides,and then the process was optimized.Because the molecular weight of polysaccharides obtained by this method is large,the combination of ascorbic acid and H₂O₂ was used as degradation reagents to prepare three low molecular weight polysaccharides.The differences of physicochemical properties,structure,antioxidant and moisturizing activities of polysaccharides before and after degradation were studied,which provided a reliable theoretical basis for the development and application of Nymphaea hybrid polysaccharides.The main findings are as follows:(1)Three methods(ultrasonic-assisted extraction,enzymatic extraction and acid extraction)were used to extract polysaccharide from Nymphaea hybrid.The acid extraction had the highest extraction rate(6.34±0.31%),while the yield of ultrasound-assisted extraction was the lowest(5.10±0.23%).Three polysaccharides contained more uronic acid and a small amount of protein and polyphenols,among which the ultrasonic method had the highest total sugar content(50.57±0.49%).Infrared spectroscopy(FTIR)showed that the primary structure of the three polysaccharides were the same.Scanning electron microscopy(SEM)and differential scanning calorimetry(DSC)experiments showed that there were differences in the apparent morphology and thermal characteristics of the polysaccharides.After purification,UNHP has stronger antioxidant capacity,the best moisturizing performance and better anti-inflammatory effect.(2)Through response surface experiment,the optimal technology of ultrasonic method was obtained as follows:ultrasonic time 30 min,liquid to solid ratio 30:1,ultrasonic power 55W,and the actual yield of polysaccharide was 6.80±0.13%.After decolorization and deproteinization,the total sugar content of UNHP was 66.47%.The effects of degradation temperature,H₂O₂ concentration and degradation time on the molecular weight of UNHP by the combination of ascorbic acid and H₂O₂ were studied.The molecular weight of UNHP was1122 k Da,and DUNHP-1(129 k Da),DUNHP-2(46 k Da)and DUNHP-3(15 k Da)were prepared by controlling the degradation time.The results of Chromatography(IC)showed that the monosaccharide type of polysaccharide was the same between UNHP and DUNHP,but the molar ratio was different.FTIR analyses revealed that the primary structure of polysaccharides was not affected after degradation.The Congo red experiment proved that none of the four polysaccharides had a triple helix structure.SEM experiments showed that the apparent morphology of polysaccharides was changed after degradation by H₂O₂-Vit C.(3)Rheological properties,functional properties,antioxidant activities and moisturizing activities of four kinds of Nymphaea hybrid polysaccharides with different molecular weight were studied.Rheological experiments showed that with the increase of degradation time,the apparent viscosity of polysaccharides decreased while the solid elasticity increased,and degradation significantly changed the rheological behavior of polysaccharides.It is found that UNHP has good oil-holding capacity and emulsifying capacity,while DUNHP has good water-holding capacity.In vitro antioxidant experiment found that the best antioxidant polysaccharide was DUNHP-2 with low molecular weight and degradation time of 60 min.The transdermal properties of polysaccharides were investigated by Franz diffusion cell test.The smaller the molecular weight of polysaccharides,the higher the skin penetration and skin retention,and the better the transdermal effect.The moisture test showed that after degradation,the moisturizing performance of polysaccharides was improved.When the ratio of UNHP,DUNHP-1 and DUNHP-3 was 1:1:1,the hydrating effect of 1%solution or 1%emulsion was better than that of the same proportion of high,medium and low molecular weight hyaluronic acid.Compared with the aqueous solution,the polysaccharides prepared into the emulsion can play an immediate and long-term moisturizing effect,and different molecular weight Nymphaea hybrid polysaccharides in the emulsion system has high stability.