The interaction of tanshinone IIA and human serum albumin (HSA) has been characterised by molecular modelling, fluorescence, Fourier transform infrared (FT-IR) and circular dichroism (CD) spectroscopic methods. The results of molecular modelling suggested that tanshinone IIA located within the binding pocket of subdomain IIA of HSA is held mainly by hydrophobic forces. Fluorescence titration revealed that tanshinone IIA could quench the intrinsic fluorescence of HSA. The binding constants at three temperatures (296, 303, and 310) K are (6.42 . 10(4), 1.54 . 10(5), and 4.35 . 10(5)) dm(3) . mol(-1), respectively. In addition, the studies of CD spectroscopy and FT-IR spectroscopy showed that the binding of tanshinone IIA to HSA changed molecular conformation of HSA. (C) 2012 Elsevier Ltd. All rights reserved.