The binding of kaempferol-3,7-α-L-rhamnopyranoside （KRR） with bovine serum albumin （BSA） was investi- gated by different spectroscopic methods under simulative physiological conditions. Analysis of fluorescence quenching data of BSA by KRR at different temperatures using Stern-Volmer methods revealed the formation of a ground state KRR-BSA complex with moderate binding constant of the order 10^4 Lomol-1. The existence of some metal ions could weaken the binding of KRR on BSA. The changes in the van＇t Hoff enthalpy （△H0） and entropy （△S0） of the interaction were estimated to be --26.53 kJ.mol-1 and 3.33 J.mol-l.K-1 and both hydrophobic and electrostatic forces contributed to stabilizing the BSA-KRR complex. According to the F6ster theory of non-radiation energy transfer, the distance r between the donor （BSA） and the acceptor （KRR） was obtained （r= 2.83 nm）. Site marker competitive experiments showed that KRR could bind to Site I of BSA. In addition, synchronous fluorescence, UV-Vis absorption and circular dichroism （CD） results indicated that the KRR binding could cause conformational changes of BSA.
