Synthesis and Biological Evaluation of Novel 2,4-Disubstituted Thiazoles for Antimicrobial and Antioxidant Activities

Abstract

Thiazole derivatives represent an important class for the development of new drugs because of their various biological activities. In this study the synthesis and biological evaluation of some new 2,4-disubstituted thiazoles obtained from 3-aryl-1H-pyrazole-4-carbaldehyde thiosemicarbazones and substituted phenacyl bromides are reported. The main purpose was to synthesize new thiazole derivatives with improved antimicrobial and antioxidant activity. Fourteen compounds (P25-P38) were synthesized by a typical reflux approach and its spectroscopic analyses viz., FT-IR, NMR, and mass spectrometry were confirmed. Antimicrobial activity was screened against different bacterial and fungal strains by well-plate method and antioxidant ability was evaluated by DPPH, nitric oxide, hydroxyl radical and superoxide anion scavenging methods. compounds P29 and P38 showing the best antimicrobial activities against all tested strains equivalent to streptomycin and fluconazole. Moreover, the majority of the synthetic derivatives revealed good antioxidant activities (DPPH scavenging efficacy >80%). Acute toxicity studies showed that the compounds were safe even upto 2000 mg/kg. Structure-activity relationship study revealed that the 2, 4-dichloro substitution on the pyrazole ring benefited the activity. The results indicate that new 2,4-disubstituted thiazoles may be considered as promising scaffolds for designing new antimicrobial and antioxidant agents with low toxicity.