Isolation, physicochemical and structural characterisation of a novel natural zinc polysaccharide from Crassostrea hongkongensis

A novel natural zinc-enriched polysaccharide: OZPs-1 was isolated from oyster (Crassostrea hongkongensis), with 922.18 mu g g(-1) of zinc. The physicochemical properties and structural features of OZPs-1 were systematically studied. The results showed OZPs-1 was predominantly composed of glucose, with a molecular weight ranging from 4 to 2044 kDa. OZPs-1 showed favourable thermal stability. NMR analysis showed that there was no sulphate substitution and C-6 substitution in OZPs-1, while C-4 might be the binding site of zinc and polysaccharide. UV, FTIR and XRD spectra suggested -OH and -COOH group might be involved in the binding of zinc to polysaccharides in OZPs-1 and there were no ZnO and sulphate substitutions in OZPs-1. These conclusions indicated that zinc might bind with -OH and -COOH in C-4 of polysaccharides and impart the stable structure and favourable physicochemical properties of OZPs-1, which could facilitate the application of OZPs-1 as natural organic zinc supplements.