Structure analysis of an acidic polysaccharide isolated from green tea

An acidic polysaccharide (ATPS-2) was isolated and purified from coarse green tea. ATPS-2 with peak molecular weight of 4430 Da was composed of rhamnose, arabinose, galactose and galacturonic acid. Structure features of the purified ATPS-2 were investigated by a combination of chemical and instrumental analysis, such as periodate oxidation, Smith degradation, (1)H NMR, (13)C NMR, COSY, HSQC, HMBC and ROESY spectrum. It was found that ATPS-2 was a pectic polysaccharide. The backbone proved to consist of the smooth region of alpha-1,4-D-galactopyranosyluronan blocks interconnected by 1,2-linked rhamnose residues involved in the linear sugar chain. The ramified hairy regions were shown to contain the following of the backbone: -->4)-alpha-D-GalpA-(1 --> 2)-alpha-L-Rhap-(1 --> 4)alpha-D-GalpA-(1--> and the side chains attached to the residues of rhamnopyranose of these fragments. The backbone galacturonic acid residues of ATPS-2 were partially O-methyl esterified and acetylated. The side chains contain linear and branched alpha-L-Araf and beta-D-Galp residues.