Hypoglycemic potential of whole green tea: water-soluble green tea polysaccharides combined with green tea extract delays digestibility and intestinal glucose transport of rice starch
Green tea is being studied extensively for its postprandial hypoglycemic effect due to its abundant catechins. Along with catechins, water-soluble green tea polysaccharides are also currently gaining attention due to their natural hypoglycemic properties. The current study investigated the combinational effect of green tea extract (GTE) and crude green tea polysaccharides (CTP) in inhibiting glucose transport after digestion of rice starch, using an in vitro digestion model with a Caco-2 cell. Co-digestion of rice starch with GTE (16.09 ± 1.02 g L−1), CTP (16.83 ± 0.81 g L−1), or GTE + CTP (17.79 ± 0.80 g L−1) hydrolyzed less starch into glucose compared with the control (18.24 ± 0.45 g L−1). Glucose transport from digesta to the Caco-2 cell after 120 min incubation was significantly inhibited with GTE + CTP (53.26 ± 4.34%). Gene expression of intestinal glucose transporters, which included sodium-dependent glucose transporter (SGLT1) and glucose transporter 2 (GLUT2), was not altered by GTE, CTP or GTE + CTP, except for the GTE-mediated upregulation of GLUT2. It is concluded that GTE + CTP lowered digestibility of rice starch with glucose and also delayed glucose uptake to the intestinal epithelium. This finding suggests a potential for green tea polysaccharides as a natural postprandial hypoglycemic substance.