INTERACTION OF PECTIN WITH THE ANTIBACTERIAL DRUG NITROXOLINE

The process of macromolecular complexation of natural polymer pectin with nitroxoline, which has antibacterial activity, was studied in order to increase the solubility of the drug and, consequently, its therapeutic efficiency. By potentiometric titration it has been shown that in dilute aqueous solutions in a wide range of slightly acidic, neutral, and alkaline pH medium, the electrostatic binding of nitroxoline with pectin occurs. In the most optimal for medical preparations neutral region pH 7 the conversion depth of this reaction was calculated. The depth of conversion of pectin carboxyl groups ɵ1 for various studied ratios P : NOC=10 : 1, 5 : 1, 3 : 1 is 0.052, 0.076, and 0.095, respectively. The corresponding values of the conversion depth for nitroxoline ɵ2 are somewhat larger and amount to 0.52, 0.38, 0.32, respectively, for the studied ratios. That is, the calculation shows that not all reactive carboxyl groups of pectin and amino groups of the medicinal substance participate in electrostatic interaction. By the viscometry method it has been established the decrease of the pectin solution viscosity in the presence of nitroxoline. This indicates that electrostatic bonding of the low molecular weight medicinal substance NOC leads to the hydrophobization of the pectin macromolecule. Comparative data, obtained by the method of derivatographic analysis, indicate, that the thermal characteristics of the studied complex of nitroxoline with pectin differ from the thermal parameters of the initial components and is thermally more stable. This confirms the formation of the product of chemical interaction - the complex of pectin with NOC.