Structural Analysis Of Abalone Viscera Polysaccharide And Its Influence On Iron Absorption

Viscera are the by-product of abalone processing.In order to promote the exploarition of the abalone viscera,in this paper,a sulfated polysaccharide?AGSP?was isolated and purified from the viscera of pacific abalone?Haliotis discus hannai Ino?by enzymatic hydrolysis technology and anion exchange chromatography.The structure of AGSP was elucidated by chemical and instrumental methods.Moreover,the Caco-2 cell model was used to evaluate iron uptake effected by AGSP and its desulfated derivative?dS-AGSP?.The homogeneity of AGSP was demonstrated by high performance gel permeation chromatography,and the result showed that the relative molecular weight of AGSP was 6.56kDa.AGSP contains neutral sugar of 76.7%,uronic acids of 19.3%,sulfated group of 11.1%and protein of 2.4%.As analyzed by GC,the component monosaccharides of both AGSP and its reduced product were mannose,glucose,galactose,besides glucuronic acid with molar ratios of 0.9:0.6:16.7:5.2 and 1.8:8.2:2:0.8:0,respectively.The structure of AGSP was revealed by LC-MS/MS,methylation,GC-MS,FT-IR and nuclear magnetic resonance?NMR?spectroscopy(¹H,¹³C,COSY,TOCSY,HSQC,DEPT and HMBC).Thus,the main structure residue of AGSP was determined as?3)-GlcA?1?3?-Gal?1?with branches at C-4 of Gal.The branches were comprised of?3?Gal?1?and some of Gal residues were sulfated at C-4.The terminals could be Gal or Glc.In addition,?4?-?-GlcA?1?2?-?-Man(1?residue and other monosaccharides such as Xyl,Fuc,and Rha also exist in AGSP but in minor amounts.The Caco-2 cell model was used to evaluate iron uptake by measuring ferritin produced in Caco-2 cell.No significant influence on relative cell viability was observed for AGSP and dS-AGSP in FeCl₂ or FeCl₃ solution according to the results of the MTT assay.Compared to FeCl₂/FeCl₃ groups,polysaccharides with lower concentrations did not significantly reduced additional Fe uptake.Polysaccharides with higher concentrations significantly inhibited additional Fe uptake.The ferritin levels of cells treated with AGSP and dS-AGSP in iron solution were significantly higher than blank.This suggested that a proportion of iron was aborbed even when it was chelated by AGSP and dS-AGSP.The iron-loading capacity,the reductive ability and iron-chelator ability of AGSP were higher than those of dS-AGSP.As indicated by the present study,overconsumption of foods containing such acidic polysaccharides may inhibit the iron absorption,while excessive iron in intestinal tract could be binded by AGSP and dS-AGSP to prevent the oxidation damage of free iron to the body.