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Abstract : |
Complexation of Zn2+ by captopril, 1-[(2S)-3-mercapto-2-methylpropionyl]-L-proline, has been studied by H-1- and C-13-NMR spectroscopy. The equilibrium constants for the trans to cis isomers bound to Zn2+ were measured for captopril by H-1-NMR spectroscopy. It is observed that the trans isomer of the drug binds more strongly to Zn2+ between pH 5 to 8. The C-13-NMR spectra show broadening of the trans isomer's resonances between pH 5 to 8, and less broadening is observed for the cis isomer's resonances in the same pH range. At higher pH, hydroxyl ions compete with the ligand, and the resonances become sharper. At lower pH (below pH 5), the captopril-Zn2+ complex gave precipitates. Mono and bidentate mixed complexation of captopril to Zn2+ is proposed., |
