Antimicrobial Activity of Novel C2-Substituted 1,4-Dihydropyridine Analogues

The antimicrobial activity of 3-methyl-5-isopropyl (or ethyl) 6-methyl-4-nitro-phenyl-1,4-dihydropyridine-3,5-dicarboxylate derivatives was evaluated. Prokaryotes (bacteria) appeared to be more sensitive to their antimicrobial activity than were eukaryotes (filamentous fungi). The best antibacterial activity was shown by derivative 33, which was able to inhibit the growth of Mycobacterium smegmatis (MIC33 = 9 μg.ml⁻¹), Staphylococcus aureus (MIC₃₃ = 25 μg.ml⁻¹), and Escherichia coli (MIC33 = 100 μg.ml⁻¹). In addition, derivative 4 demonstrated its antibacterial power on the acid-fast bacterial species M. smegmatis and on Gram-positive S. aureus. Focusing on the structure-activity relationship, it appears that the increase in the substituent bulk at the C2 position improved the antibacterial activity of the set of compounds studied. Derivatives 33 and 4, carrying 2-cyano-3-oxo-3-phenylprop-1-en-1-yl and allyliminomethyl groups, respectively, showed significantly higher inhibition activities on all tested microorganisms in comparison with the rest of the derivatives. This enhancement was also in good correlation with different log P values (lipophilicity parameter).