Comparative analysis of physicochemical characteristics of green tea polysaccharide conjugates and its decolored fraction and their effect on HepG2 cell proliferation

During plant polysaccharide extraction, polyphenols are usually oxidatively polymerized to produce quinone pigments adsorbed the macromolecular such as protein and polysaccharides. Whether these derived pigments affect the properties of polysaccharides remains unknown. In this study, green tea polysaccharide conjugates (gTPC) were prepared from low-grade green tea by means of combined-enzyme extraction followed by decoloring with anion-exchange column chromatography to obtain the corresponding fraction (gTPC-D). gTPC comprised two components, with molecular weights of 1.71 x 10(7) Da and 2.56 x 10(5) Da in mass proportions of 0.09% and 99.91%, respectively. gTPC-D consisted of one component of molecular weight 2.32 x 10(5) Da. gTPC UV-vis spectrum presented a shoulder-shaped peak, with an inflection point at 257 nm in the 240-300 nm range, whereas the spectrum of gTPC-D displayed a very weak wave-like curve in the 255-300 nm region associated with quinone pigments rather than their covalently bound protein. Quinone pigments increased the zeta potential of gTPC and reduced its water-holding capacity at high relative humidity (RH) (above 80%). gTPC-D had a significant dose-dependent inhibitory effect on HepG2 cells (p < 0.01) with an IC50 of 500 mu g/mL. These results will contribute to the quality control and large-scale production of tea polysaccharide conjugates (TPC).