Pectic polysaccharides from tea residues: Structural characterization and molecular evolution throughout in vitro...

Industrial production of tea polyphenols generates substantial quantities of waste, however, research on the comprehensive utilization of these by-products remains limited. In this study, pectic polysaccharides (OTRP) were extracted from tea residues (Xiangcha tea after polyphenol extraction) using an ammonium oxalate solution, and their physicochemical and structural properties were investigated. Methylation and NMR analyses revealed that OTRP comprised two structural domains, homogalacturonan (HG) and rhamnogalacturonan-I (RG-I), with a ratio of 1.054 ± 0.183. The HG domain featured a backbone formed by alternating 4-α-GalpA and 4-α-GalpA-6-O-methyl linkages, whereas the shorter RG-I domain was composed of 4-α-GalpA and 2-α-Rhap linkages, with side chains consisting of arabinose and galactose. Furthermore, the utilization of OTRP by the gut microbiota was evaluated in vitro. The results demonstrated that microorganisms preferentially degrade the side chains of the RG-I domain before metabolizing galacturonic acid residues from the backbone. The study provides insights into tea residue utilization.