Journal article Open Access
Ashok Vishwakarma, Alok Pal Jain, Sandeep Patel
Objective: The objective of the paper is to design, synthesis and characterization of trisubstituted 4,5-dihydropyrazoles and evaluated for their antibacterial activity.
Material and methods: The derivatives have been synthesized by the two steps process, in first step 1-(4-aminophenyl)ethan-1-one (0.002M) (1) react with 4-substituted benzaldehyde (2) to form (E)-1-(4-substituted phenyl)-3-(p-substituted)prop-2-en-1-one . The final compound (4), 1-(4-substitutedphenyl)-3-(4-substitutedphenyl)-5-(p-substituted)-4,5-dihydro-1H-pyrazole was synthesized by the reaction of compound 3 with different (4-fluorophenyl) hydrazine and (4-chlorophenyl) hydrazine. Total Sixteen compounds have been synthesized and characterized by physicochemical and spectral analysis. The final compounds (TDHP-1 to TDHP-16) have been evaluated for antibacterial activity by disk diffusion method.
Result and Discussion: The synthesized compounds have characterized by the IR, 1HNMR and mass spectral analysis. The IR spectrum of the compounds has shown the characteristics peak (cm-1) at 3012 (C–H), 2912 (C–H), 1675 (C=C), 1595 (C-C), 1462 (C=N), 1308 (C-H), 1512 (N=O), 1334 (N-O), 745 (C-Cl), 1018 (C-Br); 1102 (C-F). The 1HNMR spectra of synthesized compounds depicted the peak at δ7.23-8.62 (m, 4H, CH=CH-CH=CH), 7.03-8.80 (m, 3H, Ar-H), 3.08, 2.47 (d, 2H, CH2), 3.42 (d, 1H, C-5, CH), 11.431 (s, 1H, NH). The Data of antibacterial activity against the gram-positive bacterial strains (Bacillus subtilis and Staphylococcus aureus) suggested that among substituted pyrazoline derivatives (TDHP-1 to TDHP-16), compound TDHP-2, TDHP-3, TDHP-4, TDHP-5, TDHP-6, TDHP-7, TDHP-8 have shown best activity against gram positive bacteria and The Data of antibacterial activity against the gram-negative bacterial strains (Salmonella typhimurium and Pseudomonas aeruginosa) suggested that among substituted pyrazoline derivatives (TDHP-1 to TDHP-16), compound TDHP-1, TDHP-2, TDHP-3, TDHP-4, TDHP-5 TDHP-6, TDHP-7, TDHP-8 have shown best activity against gram negative bacteria.
Conclusion: In general, trisubstituted 4,5-dihydropyrazoles derivatives having amine termination has shown the better anti-microbial activity as compared to standard drug. There is a need in drug design strategy to achieve more anti-microbial potency in different bacterial strain on novel future synthetic heterocyclic compounds.
Keywords: Antimicrobial activity, disk diffusion method, antibacterial, pyrazole, gram positive