Characterization and Antioxidant Activity of the Complex of Tea Polyphenols and Oat β-Glucan

Few data are available about the effects of complexation of polyphenols with polysaccharide on their bioavailability. The complex of tea polyphenols (TP) with oat beta-glucan was characterized by ultraviolet-visible spectrometry, Fourier transform infrared spectrometry, differential scanning calorimetry, atomic force microscopy, and solid-state C-13 NMR spectroscopy. The results indicated that the bonds which governed the interaction between TP and oat beta-glucan were strong hydrogen bonds. The in vitro antioxidant activity of TP, beta-glucan, their complex, and physical mixture was assessed using four systems, namely, DPPH center dot, OH center dot, and O-2(center dot-) scavenging activities and reducing power. The complexation and blending of TP and beta-glucan exhibited different impacts on the index of in vitro and in vivo antioxidant capacities. In the concentration range of 0.5-2.5 mg mL(-1),the complex had highest O-2(center dot-) scavenging activity, whereas the highest OH center dot scavenging activity was found with the physical mixture. For antioxidant testing in vivo, there was no significant difference between the complex and the physical mixture in terms of glutathione peroxidase activity and levels of malondialdehyde and total antioxidant capacity in serums. However, the complex exhibited much higher activities of superoxide dismutase and glutathione peroxidase in livers than the physical mixture. The present study provided a deeper understanding of the influence of molecular interaction between TP and oat beta-glucan on their antioxidant activities.