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ELECTROCHEMICAL STUDY OF CURCUMIN on carbon Electrode ( electrochemical-study-curcumin-carbon-electrode )

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ACADEMIA ROMÂNĂ Revue Roumaine de Chimie http://web.icf.ro/rrch/ Rev. Roum. Chim., 2010, 55(2), 109-115 ELECTROCHEMICAL STUDY OF CURCUMIN AND bisDEMETHOXYCURCUMIN ON ACTIVATED GLASSY CARBON ELECTRODE Andreea LUNGU,a Ileana SANDU,a Cristian BOSCORNEA,b Stefan TOMASb and Constantin MIHAILCIUCa* a Physical Chemistry Department, Faculty of Chemistry, University of Bucharest, Regina Elisabeta 4-12, 030018 Bucharest, Roumania; b. Organic Technology and Macromolecular Compounds, Faculty of Applied Chemistry and Material Sciences, University Politehnica of Bucharest, Calea Victoriei 149, 00702 Bucharest, Roumania Received June 10, 2009 The curcumin and a curcumin-like compound were investigated by using cyclic voltammetry (CV) and differential pulse voltammetry (DPV) techniques at an anodically activated glassy carbon electrode (GCE) in non-aqueous media. The presense of two o-methoxy phenolic groups in curcumin in comparison with its analogue determines different cyclic voltammetric redox behaviour of curcumin and its analogue. The anodically activated GCE leads to a better electrochemical behaviour (much better defined and more stable peak currents) of the two compounds in comparison with their behaviour at the bare GCE. Both of the two compounds are adsorbed but in different degree to the anodically activated GCE surface. INTRODUCTION∗ Curcumin is the main pigment present in the rhizomes of the Curcumina longa possessing biological properties as anti-inflammatory, anti- angiogenic, antioxidant, etc. It inhibits free radical formation in blood and body tissues. It also prevents some cardio-vascular deseases.1,2 The powerful curcumin antioxidant activity,3-5 working especially when diverse free radicals are produced as a result of physiological processes, is essentially an electrochemical property, so it has to be investigated from an electrochemical viewpoint in order to characterize its redox behaviour and its electrocatalytic role. The curcumin (1,7-bis[4-hydroxy-3-methoxy- phenyl]- 1,6-heptadiene-3,5-dione) and its analogue bisdemethoxycurcumin (1,7-bis[4-hydroxyphenyl]- 1,6-heptadiene-3,5-dione) (see Fig. 1) exhibit different redox properties due to the presence of ∗ Corresponding author: cmpaul@gw-chimie.math.unibuc.ro methoxy group in position 3 of the phenyl moiety in curcumin. Also the curcumin can be an efficient chelating agent for different metallic cations as Fe3+ , Fe2+ , Co2+ , and Ni2+ leading to formation of complexes,6-12 besides it can inhibit the oxidation of certain metal ions.7,10 Both studied curcumins have the same moiety (i.e., bis-α,β-unsaturated β-diketo(heptadiene- dione)) and undergo keto-enol tautomerism. The biological activity of curcumin is associated with the phenolic hydroxyl group and the diketonic structure13 especially under pH 8, where the ketonic form of the heptadieno-dione chain predominates. Above pH 8, the enolate form of the heptadieno-dione chain predominates and curcumin exhibites kelatic properties towards the cations as Fe3+ , Fe2+ , Cu2+ , Cd2+ and Ni2+ , the enolate form of curcumin acting as electron donor and good coordination sites. Curcumin can



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