The binding reaction between camptothecin derivatives, such as topotecan hydrochloride (THC) and irinotecan hydrochloride (IHC), and bovine serum albumins (BSA) was studied by fluorescence and UV-Vis absorption spectra. The research results indicate that the combination reaction of them was a single static quenching process, and camptothecin derivatives strongly bound BSA with the molar ratio of 1∶1 and the binding equilibrium constant K₀ at 25 ℃, K_0,THC＝7.73×10⁵ L/mol, K_0,IHC＝4.73×10⁵ L/mol. The shortest binding distance r and energy transfer efficiencies E between donor BSA and acceptor of camptothecin derivatives were obtained by Förster nonradiative energy transfer mechanism as follows, r_THC＝3.75 nm, r_IHC＝3.08 nm and E_THC＝0.26, E_IHC＝0.51. And the effect of some ions on the binding reaction between camptothecin derivatives and BSA was investigated to find the main sort of binding force between them to be both hydrophobic force and dipole force.

Key words: topotecan hydrochloride, irinotecan hydrochloride, camptothecin derivative, BSA, fluorescence quenching, binding reaction