Binding of curcumin, an antioxidant and anti-tumor agent to human serum albumin (HSA) has been investigated by following absorption and fluorescence spectral changes in HSA and curcumin. From the temperature dependent fluorescence changes and kinetic measurements using stopped-flow spectrometer, enthalpy and entropy changes and activation energy for the binding of curcumin to HSA were evaluated. Following fluorescence resonance energy transfer (FRET) between excited tryptophan in HSA and HSA bound curcumin, the critical transfer distance and mean distance between tryptophan-214 in HSA and curcumin were estimated. Effect of chemical and thermal denaturation of HSA on curcumin fluorescence was also studied. (c) 2007 Elsevier B.V. All rights reserved.