Facile Synthesis, Antimicrobial Studies and Structure - Activity Relationship Studies of Some Novel Pyrazole Analogs

Background: The pyrazole moiety hold a unique position in heterocyclic chemistry. Novel pyrazole scaffolds with more potency can be very effective against resistant strains of various microorganisms. Objective: To carry out the synthesis, characterization and antimicrobial screening of novel 3, 5 dimethyl pyrazole analogs. Method: A series of novel pyrazole scaffolds were synthesized by treating 3, 5 dimethyl pyrazole with various propionamide under nitrogen atmosphere. Compounds were evaluated for their in vitro antibacterial activity in comparison to ciprofloxacin and norfloxacin, against both Gram-positive (S.aureus, B.subtilis) and Gram-negative (E.coli, P.aeruginosa, S.typhi, K.pneumonia) bacteria. They were also screened for their antifungal activity against C.albicans and A.niger using fluconazole as a standard drug. Results: The structures of synthesized pyrazole analogs were successfully elucidated using their 1H NMR, Mass, IR, elemental analysis data. Compounds 28 and 29 showed a relatively good inhibitory profile against both Gram-positive and Gram-negative bacteria. Compound 21, 28 and 29 were found to be more active against both Gram-positive bacteria and compound 26, 28, 29, and 38 exhibited good inhibitory activity against all Gram-negative bacteria. Antifungal screening results showed that compounds 20, 22, 25, 26, 27, 30, 31, 32, 33, 36 and 37 were equally potent when compared to fluconazole. Thus, from the results of anti-microbial screening data, it was evident that the presence of a halogen group at different positions of the aromatic ring was responsible for their potency. Conclusion: These newly synthesized pyrazole analogs are better scaffolds to be developed as broad spectrum chemotherapeutic agents.