Title
Excited state tautomerization of camptothecin in aqueous solution
Document Type
Article
Publication Date
11-15-1996
Abstract
The effect of pH on the absorption and fluorescence spectral characteristics of 20(S)-camptothecin was studied in aqueous solution. In alkaline solution, the lactone ring of camptothecin hydrolyzes to produce camptothecin carboxylate. The equilibrium constants of the lactone ring hydrolysis of camptothecin at various pH values were determined using steady state fluorescence measurements. The 1H nuclear magnetic resonance (NMR) and circular dichroism spectra were measured to characterize the structure of camptothecin in strongly alkaline medium. The fluorescence intensity of camptothecin is quenched by OH- ions. A mechanism of fluorescence quenching of the carboxylate form by OH- ions, which involves tautomerization on electronic excitation, is proposed. The ground and excited state pKa values of the quinolinium ion are reported.
Publication Source (Journal or Book title)
Journal of Photochemistry and Photobiology A: Chemistry
First Page
21
Last Page
27
Recommended Citation
Dey, J., & Warner, I. (1996). Excited state tautomerization of camptothecin in aqueous solution. Journal of Photochemistry and Photobiology A: Chemistry, 101 (1), 21-27. https://doi.org/10.1016/S1010-6030(96)04405-X