Preparation And Biological Evaluation Of Chemical Modified Polysaccharides From Sargassum Fusiforme

Sargassum fusiforme,a type of brown algae widely distributed in China,Korea and Japan,has been applied as a therapeutical agent for thousands of years.The polysaccharides extracted from S.fusiforme have been demonstrated to have multiple activities,such as antitumor,vibriosis resistance,enhancing immunity and anti-hyperlipidemia.Generally speaking,the biological activities of polysaccharides are considered to be correlated with the molecular weight,space structures,as well as the nature,quantity and position of substituents.It has been showed that the low activity(antioxidant,anti-tyrosinase,antimicrobial)of S.fusiforme(SF)is difficult to meet the demand,and the chemical modification of polysaccharides were mostly concentrated in sulfurization and selenylation methods.In the present study,in order to improve the antioxidant activity,anti-tyrosinase activity and antimicrobial activity of polysaccharides derived from SF,degraded polysaccharide with relatively low molecular weight was obtained from SF,and its carboxylmethylated and hydroxamated derivatives were successfully prepared.In addition,their in vitro antioxidant activity,anti-tyrosinase activity and antimicrobial activity were investigated.The main results that we have obtained are as follows:1.Crude polysaccharide(PSF)was extracted from Sargassum fusiforme with hot water.The degradaded polysaccharide was prepared by using ascorbic acid in combination with H2O2.The degradation conditions were optimized using a Box-Behnken response surface design(BBRS).The optimum conditions were established as:concentration of ascorbic acid(Vc)and H2O2 17.26 mM,degradation temperature 51℃and degradation time 1.6 h.2.Carboxymethylation of DPSF was carried out in the presence of monochloroacetic acid,providing the carboxymethylated polysaccharide(CDPSF).The reaction of CDPSF with hydroxylamine in the presence of 1-ethyl-3-(3-dimethylaminepropyl)carbodiimide(EDC)yielded the hydroxamated polysaccharide(HCDPSF).The chemical components of PSF and DPSF had no significant difference.The molecular weight of PSF and DPSF were determined to be 987 and 407 kDa by High performance Gel Permeation Chromatography(HPGPC).GC-MS was employed to analyze the monosaccharide composition.The results of GC-MS indicated that PSF,DPSF and CDPSF were mainly made up of fucose,galactose,as well as small portions of glucose,xylose and mannose.The successful structural modification of CDPSF and HCDPSF-2 were confirmed by IR,1H NMR and 13C NMR.3.In vitro antioxidant activity of the polysaccharides was evaluated by determining their radical(hydroxyl radical,superoxide anion radical and DPPH radical)scavenging abilities,and ferric iron reducing power.It was found that the antioxidant activity of DPSF was greatly increased as compared to that of PSF,while the modified polysaccharides CDPSF and HCDPSF-2 possess the stronger scavenging ability than DPSF.The inhibitory activity on tyrosinase of PSF and DPSF were also evaluated,the result showed that DPSF has superior anti-tyrosinase effect to that of the PSF.DPSF is a competitive-uncompetitive mixed type inhibitor.4.Bacillus subtilis,Staphylococus aureus,Escherichia coli,Pseudomonas aeruginosa and Salmonella spp were selected as the tested strains.The antimicrobial activity of all samples against the five strains was evaluated by determining the inhibition zone and minimum inhibition concentrations(MIC)values.The results demonstrated that CDPSF and HCDPSF possess marked inhibitory activity,however,such inhibitory effects were not found for PSF and DPSF.