Studies on the relationship between the structure of pyrimidinecarboxylic, pyridazinecarboxylic and pyrazinecarboxylic acids and their antimicrobial and cytotoxic activity

Abstract

Diazinecarboxylic acids (pyridazine-3-carboxylic, pyridazine-4-carboxylic, pyrimidine-2-carboxylic, pyrimidine-4-carboxylic, pyrimidine-5-carboxylic and pyrazine-2-carboxylic acids) were characterized by means of spectroscopic (FT-Raman, FTIR, UV, 1HNMR, 13CNMR) and thermogravimetric analysis as well as antimicrobial and cytotoxic tests. The structures of diazinecarboxylic acids were calculated by the DFT method (B3LYP/6-311G(d, p). For the most stable conformers, the energy of HOMO and LUMO molecular orbitals, the geometric (HOMA, GEO, EN, I6) and magnetic (NICS) aromaticity indices, NBO electronic charge distribution, sEDA and pEDA indexes, Wiberg Bond Order, Wiberg Index and theoretical IR and NMR spectra have been calculated. The energies of protonating and deprotonating acids were also calculated. The effect of the nitrogen heteroatom position in the aromatic ring in relation to the position of the carboxyl group on the electronic charge distribution, thermal stability, antimicrobial and cytotoxicity activities of the examined acids was determined. Antimicrobial activity of tested acids against of Escherichia coli, Bacillus subtilis, Pseudomonas aeruginosaand Candida albicanswas calculated based on MTT colorimetric assay (MCA). The cytotocic effect of diazynecarboxylic acids was examined in A375 melanoma cell line and DLD-1 cell line. A biplot analysis was performed in order to determine the correlations between selected parameters of the tested compounds and relative cell viability of E. coli, B. subtilis, P. aeruginosa, C. albicans, A375 and DLD-1 cell lines. Thermal behaviour of all investigated carboxylic acids was investigated using thermogravimetry (TG) and differential scanning calorimetry (DSC) techniques in flowing air atmosphere. All compounds are stable in room temperature.