Biological activity of new schiff base compounds derived from substituted 3-aminopyrazoles, the role of pyrazole on bioactivity

Abstract

A series of new Schiff base compounds derived from substituted 3-aminopyrazoles and dialdehydes were synthesized and characterized by 1H, 13C nuclear magnetic resonance, Fourier-transform infrared, ultraviolet-visible, gas chromatography-mass spectrometry and high resolution mass spectrometry. The antimicrobial activity of the ligands was screened against the bacterial Gram-negative species Escherichia coli, Pseudomonas aeruginosa and the Gram-positive species Staphylococcus aureus, using gentamycin as a control. Minimal inhibitory concentration was determined by the microdilution method. The anticancer activity was evaluated against HCT116 colorectal cancer cells, with etoposide as a control, using MTS-PMS assay and expressed as IC50 values. The pharmacological studies showed that in general ligands exhibited broad-spectrum antibacterial activity, which decreased in the following order Escherichia coli>Staphylococcus aureus>Pseudomonas aeruginosa. Bis(imino)pyridine Schiff bases (2a-e) have excellent activity towards Staphylococcus aureus; compounds 2a and 2d (3.125 μg/ml) are several times more potent than the control drug, whilst bis(imino)benzene compounds (3a-e) showed significant pathogenic activity toward Pseudomonas aeruginosa with MIC values of 6.25 μg/ml for 3c and 3e. Compound 2c showed higher cytotoxicity (0.40 μM) than etoposide. The results suggest that pyrazole ring as well as the substitution pattern on the heterocyclic moiety have effect on bioactivity.