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  • Author: Ž. Bezáková x
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Study of stability of potential betaadrenolytics, derivatives of the [(arylcarbonyl)oxy]aminopropanol by kinetics of alkaline hydrolysis

This work deals with the study of the stability of six derivatives of the [(arylcarbonyl)oxy]amino propanol with carbamate substitution on the benzene ring. The studied compounds are different in the substitution on the amine group in the side chain as well as in the substitution on the carbamate functional group. The hydrolysis of compounds was measured in the aqueous-ethanol sodium hydroxide solution (0.1 mol.l-1) at 25, 37, 45 and 60°C spectrophotometrically in the ultraviolet and visual regions. The studied compounds possess two functional groups, which undergo hydrolysis. The pseudo-first order rate constants of hydrolysis for individual reaction steps were determined. The ester functional group of compounds hydrolyses very quickly in this medium. The compounds possessing the tertiary substitution on the amino group are less stable toward alkaline hydrolysis. The course of hydrolysis of compounds was also investigated by thin layer chromatography (TLC).

Abstract

The substance BK 129 - 1-[2-(2-pentyloxyphenylcarbamoyloxy)-(2-methoxymethyl)-ethyl]-perhydroazepinium chloride was prepared in terms of influence of the connecting chain between the carbamate functional group and the basic part of molecule on biological activity. Such a structural feature is important with regard to its stability. In this work we determined the rate constants of alkaline hydrolysis of this compound at increased temperature under isothermal and non-isothermal conditions. The hydrolysis was also performed in buffer solutions with the purpose of evaluating its stability. Non-isothermal tests of stability enable to reduce the number of analyses. The necessary data for stability of compound are in this way achieved in a short time.

Abstract

The aim of this paper is the study of physico-chemical properties of the chosen compounds, derivatives of 2-hydroxy-3-[2-(4-methoxyphenyl) ethylamino]propyl-4-[(alkoxycarbonyl)amino]benzoates and 2-hydroxy-3-[2-(2-methoxyphenyl)ethylamino]propyl-4-[(alkoxycarbonyl) amino]benzoates with potential ultra-short beta-adrenolytic activity. The studied compounds are different in the position of the substituent on the benzene ring in the side chain as well as in the aromatic ring in position 4 with alkyl- (methylto butyl-) carbamate. The physico-chemical characteristics, for example, lipophilicity, surface activity, adsorbability, acidobasic properties etc., are very important for the explanation of the relationship between structure and biological activity of the drug. These parameters serve as the base of quantitative structure-activity study. The goal of this work is to establish the spectral characteristics of studied compounds in UV-area, pKa values, the parameters of lipophilicity (the values of Rf and RM from thin layer chromatography, retention time t´R and capacity factor k´ from liquid chromatography and experimental partition coefficients log P´ values), surface tension, critical micelle concentrations, the adsorbability of compounds expressed by percent of adsorbed compound on active charcoal β% as well as by Freundlich adsorption isotherms. The obtained values are correlated with the parameters characterising the size of molecule, for example, the number of carbon atoms on carbamate functional group.

Abstract

In this manuscript was investigated behaviour of drug valsartan by micellar media of anionic surfactant sodium dodecyl sulphate. As the method was used electrical conductivity for the determination of critical micelle concentration at different temperatures (T = 293.15 - 313.15 K), as well as calculated thermodynamic parameters like standard Gibbs free energy, enthalpy and entropy of micellization. According to contribution of Gibbs free energy is the process of micellization primarily controlled by entropy. Solubilization of valsartan was studied in surfactant system at 298.15 K and physiological conditions pH 7.4 using UV-spectrophotometry at different concentration range (0.001 - 0.07 mol/l) of sodium dodecyl sulphate. The solubilization of drug was observed with increasing concentration of surfactant in aqueous solution.

Abstract

The aim of this work is the study of stability and kinetics of hydrolysis of the chosen compounds, derivatives of 2-hydroxy-3-[2-(4-methoxyphenyl)ethylamino]propyl-4- [(alkoxycarbonyl)amino]benzoates and 2-hydroxy-3-[2-(2-methoxyphenyl)ethylamino] propyl-4-[(alkoxycarbonyl)amino]benzoates with potential ultra-short beta-adrenolytic activity. The studied compounds are different in the position of the substituent on the benzene ring in the side chain as well as in the aromatic ring in position 4 with alkyl- (methyl- to butyl-) carbamate. Thin layer chromatography and UV-area spectrophotometry are used in order to establish the stability of these potential pharmaceuticals. The stability studies of the compounds were examined in acidic and alkaline media, in buffers and due oxidation at room and at elevated temperature chromatographically, and Rf values of incipient products and degradation products were detected. Kinetics of acid and base hydrolysis in various solutions at temperatures 80 °C and 100 °C were examined through UV-area spectrophotometry. Kinetic parameters such as rate constant k, half-life period t1/2 and usable life t90 were determined.