Free radical scavenging ability and antioxidant efficiency of curcumin andits substituted analogue

Free radical reactions of curcumin and its ethoxy substituted derivative (C 1) 1,7-bis-(4-hydroxy-3-ethoxy phenyl)-1,6-heptadiene-3,5-dione have been s tudied using a pulse radiolysis technique in homogeneous aqueous-organic so lutions like acetonitrile-water and isopropanol-water mixtures, as well as in neutral TX-100 and cationic CTAB micellar solutions. The phenoxyl radica ls of curcumin or C1 were generated by one-electron transfer to several oxi dants like N-3(.), Br-2(-.), CCl3O2., glutathione radicals which exhibit ab sorption from a 300-600-nm wavelength region with the maximum at 490-500 nm . Other important properties of the phenoxyl radicals such as extinction co efficient, radical lifetime and their formation and decay rate constants we re also determined in these systems. The antioxidant property of curcumin a nd C1 were estimated in terms of their ability to inhibit the lipid peroxid ation in liposomes and also in terms of trolox equivalent antioxidant capac ity (TEAC). The results were compared with alpha-tocopherol. (C) 1999 Elsev ier Science B.V. All rights reserved.