Comparison of polysaccharides isolated from Ganpu tea of different storage ages: Chemical, structural, and hypoglycemic properties

This study investigated the structural characteristics and hypoglycemic activity of polysaccharides isolated from Ganpu tea (GPT) in different storage periods. Three polysaccharide fractions (GPTPS1-E2, GPTPS3-E2, and GPTPS5-E2, representing 1, 3, and 5 years of storage, respectively, where GPTPS is Ganpu tea polysaccharides) were extracted and purified from GPT. Chemical composition analysis revealed that all fractions were predominantly acidic polysaccharides with total sugar content exceeding 90%. Monosaccharide composition analysis showed galacturonic acid as the primary component, along with significant amounts of galactose and arabinose. Molecular weight distribution showed that different fractions had distinct distributions, with GPTPS1-E2 and GPTPS3-E2 showing the highest and lowest molecular weights, respectively. Fourier-transform infrared and nuclear magnetic resonance spectroscopy provided insights into the structural characteristics of the polysaccharides. Scanning electron microscopy and X-ray diffraction analyses revealed distinct surface morphologies and crystalline structures. The hypoglycemic activity was evaluated using a Caco-2 cell model, demonstrating potential antidiabetic properties via the IRS1-GLUT2-SGLT1 axis. Comparative analysis revealed that storage time could influence the structural characteristics and hypoglycemic activity of GPTPSs, with a certain storage time generally associated with the transformation of structural characteristics related to hypoglycemic activity and the enhanced hypoglycemic effect. This research contributes to the understanding of GPTPS and their potential applications in functional foods and nutraceuticals.