Synthesis of Heterocyclic Mesoionic Betaines Derivatives containing a Pyrimidine Ring for screening of their Biological Activities

In the present study, a series of mesoionic pyrimidinium betaines obtained by condensation of α- -aminopyridine or N, N’- disubstituted amidines with substituted malonic esters was tested for in vitro antimicrobial activity against two bacteria: Gram-positive Staphylococcus aureus, Gram-negative Escherichia coli and three fungi: Aspergillus carbonarius, Fusarium culmorus and Mucor ramannianus to assess their potential use as antimicrobial agents using a well diffusion. These betaines are bicyclics 3, 4 monocyclic 6 and fatty betaine type of amphoteric surfactant 7. The synthesized compounds were found to exhibit moderate to high antifungal against the tested fungi. On the other hand, it was observed that most of the tested compounds revealed moderate antibacterial activity against Staphylococcus aureus while fatty chain betaine type amphoteric surfactant exhibited the best antibacterial activity. Whereas all compounds were found inactive against Gram-negative Escherichia coli. Investigation of antimicrobial activity of the synthesized compounds demonstrated that the meso-ionic nature of pyrimidinium betaines, the presence of the pyrimidine ring biologically active in their structure, the long hydrocarbon chain in fatty betaine and extended delocalization of electrons probably influenced the extent of antimicrobial activity and contributed to the remarkable inhibitory activity of these compounds. Based on these results, it can be assumed that pyrimidinium betaines could be useful in the development of new antimicrobial medicines and may be potential sources of new drugs effective against various infectious diseases.