Abstract
A validated UV/VIS method for preliminary determination of the chemical stability and stability in close to physiological conditions of a model pyrrole hydrazide and its corresponding derivative, bearing susceptible to hydrolysis hydrazone group was developed. The evaluated substances were subjected to the influence of a variety of pH medias, representing the main physiological values of 37°C and corresponding pH values in the stomach (pH 2.0), blood (pH 7.4) and small intestine (pH 9.0). The chemical stability at strong alkali media of pH 13.0 was also evaluated. The hydrazide was found to be stable at all investigated conditions. The tested hydrazone was determined to be stable at pH of 7.4 and a temperature of 37°C and susceptible to hydrolysis at strong acidic (pH 2.0) and moderate alkali (pH 9.0) media at the same temperature. In addition, a decrease in the absorption at strong alkali media (pH 13.0) was observed, showing the compounds instability under these conditions.
Highlights
Pyrrole and its derivatives play a fundamental role in pharmaceutical and natural chemistry
The investigated hydrazide was synthesized according to a general synthetic procedure, presented elsewhere (Tzankova, 2017)
We considered as the most probable change in compound D_5a to be cleavage of the characteristic hydrazone group -CH=N
Summary
Pyrrole and its derivatives play a fundamental role in pharmaceutical and natural chemistry. In the recent years the synthesis, reactions and biological activities of pyrrole derivatives are of great interest of many researches (Jones, 1990). Pyrrole and its derivatives are found as components of many polymers, dyes and larger aromatic rings (Wurz, 2005; Piliego, 2010; Katritzky, 1989). Some of these compounds are useful intermediates in the synthesis of biologically important naturally occurring alkaloids and synthetic heterocyclic derivatives (O’Hagan, 2000; Chinchilla, 2004)
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