Synthesis, characterization and in vitro anti-diabetic activity of catechin grafted inulin

In this study, a novel biological macromolecule with strong in vitro anti-diabetic activity was developed by grafting catechin onto inulin via a free radical mediated method. The characterization, alpha-glucosidase and alpha-amylase inhibitory activities of catechin grafted inulin (catechin-g-inulin) were investigated. Results showed that the grafting ratio of catechin-g-inulin was 124.8 mg CAE/g. UV-vis spectrum of catechin-g-inulin exhibited a new band at 280 nm, attributing to B ring of catechin moiety. FT-IR spectrum of catechin-g-inulin showed new absorption bands between 1540 and 1418 cm(-1), attributing to C=C stretching vibration of catechin moiety. H-1 NMR spectrum of catechin-g-inulin preserved all the characteristic proton signals of inulin and partial signals of catechin. These all confirmed the successful grafting copolymerization. Conjugation probably occurred between OH of inulin (C-6) and H-6/H-8 of catechin (A ring). Catechin-g-inulin also exhibited increased thermal stability and crystallinity as compared to inulin. Moreover, in vitro anti-diabetic assays showed the alpha-glucosidase inhibitory activity decreased in the order of catechin-g-inulin>catechin>acarbose>inulin, and alpha-amylase inhibitory activity decreased in the order of catechin-g-inulin>acarbose>catechin>inulin. These indicated the potential of catechin-g-inulin in the development of a novel effective anti-diabetic agent. (C) 2013 Elsevier B.V. All rights reserved.