Effective utilisation of tea residues: physicochemical characterisation and hypoglycemic activity of cell wall polysaccharides prepared by sequential extraction

Abstract Tea residues are usually discarded as worthless waste, resulting in resource waste and environmental pollution. This study focussed on extracting water-soluble polysaccharides (W-TPS) from green tea residues and further isolating four tea cell wall polysaccharides (C-TCWP, N-TCWP, 1 K-TCWP, and 4 K-TCWP) using 1,2-cyclohexanediaminetetraacetic acid, saturated sodium carbonate, 1 mol/L potassium hydroxide (KOH), and 4 mol/L KOH, respectively. The study characterised these polysaccharides, revealing differences in chemical composition, monosaccharide composition, and morphology. Importantly, the research demonstrated the digestibility of W-TPS and TCWPs and highlighted the potent hypoglycemic activity of 5 polysaccharides. Furthermore, cell-based experiments indicated the potential of W-TPS and 4 K-TCWP in ameliorating insulin resistance. Notably, 4 K-TCWP exhibited promising results by significantly increasing glucagon gene expression and enhancing glucagon-like peptide-1 secretion in NCI-H716 cells. This study underscores the potential of tea cell wall polysaccharides as valuable bioactive compounds for managing blood sugar levels and emphasises the efficient utilisation of tea residues.