α-glucosidase inhibition of natural curcuminoids and curcumin analogs

Natural curcumin (1), demethoxycurcumin (2) and bisdemethoxycurcumin (3) isolated from Curcuma longa (turmeric), and synthetic curcumin analogs (A(1-7), B1-7, C1-6 and D1-7) were evaluated in vitro for the a-glucosidase inhibitory activity via UV and circular dichroism (CD) spectroscopy. The results indicated that natural curcuminoid compound 3 showed a remarkable inhibitory effect with IC50 of 23.0 mu M, and the synthetic compounds A(2), B-2, C-2 and D-2 showed potent inhibitory effects with IC50 of 2.8, 2.6, 1.6 and 8.2 mu M, respectively. Kinetic study exhibited that the mechanism of alpha-glucosidase inhibition of both 3 and C-2 was non-competitive. The structure activity relationship revealed that the ortho dihydroxyl groups could form a more tight interaction with a-glucosidase to exert more potential inhibitory activities. (c) 2006 Elsevier SAS. All fights reserved.