Comparison and structural characterization of polysaccharides from natural and artificial Se-enriched green

Se-enriched green tea has been widely used as a functional food and disease prevention. In this study, two kinds of homogeneous polysaccharides namely ASe-TPS2 and NSe-TPS2 were obtained from artificial and natural Se enriched teas with the molecular weights of 6.73 x 10(3) Da and 2.44 x 10(5) Da. The structures of ASe-TPS2 and NSe-TPS2 were characterized by monosaccharide composition analysis, partial acid hydrolysis, methylation, FT-IR spectroscopy, NMR spectroscopy, SEM and TGA analysis. It showed that ASe-TPS2 and NSe-TPS2 were acidic polysaccharides containing high amount of uronic acid. The structure of the ASe-TPS2 was mainly composed of beta-D-(1 -> 3)-Glcp, alpha-D-(1 -> 4)-GalpA, (1 -> 4)-Glcp, alpha-L-(1 -> 2)-Rhap and alpha-D-(1 -> 4)-GalpA, and the non-reducing ends were mainly composed of Araf and Xylp. However, the NSe-TPS2 was mainly composed of beta-D-(1 -> 4)-Glcp and alpha-D-(1-4 -> 4)-GalpA, and the branches were mainly composed of beta-L-(1 -> 2)-Araf, alpha-D-(1 -> 3)-Galp and beta-L-(1 -> 2)-Rhap whereas the non-reducing ends were mainly composed of Glcp and Galp residues. These results suggested that the distinction of selenylation methods could present different polysaccharide chain structures. (C) 2019 Published by Elsevier B.V.