Polarographic determination of parameters of complexing between the virostatic 1-ethyl-isatine-3- isothiosemicarbazone and copper ions

Abstract

Cancerostatic and virostatic activities of inhibitor substances may be correlated with their complexing tendency with metal ions, which play an important role in enzymatic reactions. Therefore, the equilibrium constant K β and coordination number β of the 1-ethyl-isatine-3-isothiosemicarbazone-copper complex were estimated from polarographic titrations by means of a general data-fitting program for non-linear regression. We suggest there is an immediate formation of a 1:2 complex with K β = (1.94±0.27) 10 9 M −2 and β = 2.11 ± 0.02. The experimental technique used is derivative polarography of the diffusion current of copper ions, since the peak height was found to be proportional, to sufficient precision, to the free copper ion concentration. The emphasis in this paper is on the methodology, because the data analysis described applies to any system that obeys the same complexing model. It was found that the complexing tendency of isatine isothiosemicarbazones parallels the virostatic or bacteriostatic activity, respectively.