The isonicotinoyl hydrazide derivatives were prepared by the reaction between the corresponding substituted benzaldehyde

(10 mmol) with isoniazid (10 mmol) in ethanol (30 mL). After refluxing for 4–5 h, the resulting mixture was concentrated.18 The residue was purified by washing with cold ethanol which afforded the pure derivatives. Benzylideneisonicotinohydrazide Selleckchem 3 Methyladenine (A1): UV–Visible (λmax, nm): 257, 350; FT-IR (υ cm−1, KBr): 1554 (C]N), 1678 (C]O), 3064 (NH); 1H NMR (DMSO-d6, δ ppm): 12.1 (NH), 8.3 (N]CH), 7.4–8.8 (Aromatic protons); 13C NMR (DMSO-d6, δ ppm): 162.5 (C]O), 150.2 (C]N), 109.7–153.7 (Aromatic carbon). (2,3-Dimethoxybenzylidene)isonicotinohydrazide (A2): UV–Visible (λmax, nm): 257, 352; FT–IR (υ cm−1, KBr): 1568 (C]N), 1664 (C]O), 3064 (NH); 1H NMR (DMSO-d6, δ ppm): 12.1 (NH), 8.3 (N]CH), 3.8

(OCH3), 7.2–8.8 (Aromatic SAHA HDAC protons); 13C NMR (DMSO-d6, δ ppm): 161.0 (C]O), 150.6 (C]N), 60.6 & 66.4 (OCH3), 118.9–157.4 (Aromatic carbon). The benzohydrazide derivatives were prepared by the reaction between the corresponding substituted benzaldehyde (10 mmol) with benzhydrazide (10 mmol) in ethanol (30 mL). After refluxing for 4–5 h, the resulting mixture was concentrated. The residue was purified by washing with cold ethanol which afforded the pure derivatives. Benzylidene-benzohydrazide (C1): UV–Visible (λmax, nm): 257, 331; FT-IR (υ cm−1, KBr): 1544 (C]N), 1641 (C]O), 3043 (NH); 1H NMR (DMSO-d6, δ ppm): 11.2 (NH), 8.3 (N]CH), 7.2–8.8 (Aromatic protons); 13C NMR (DMSO-d6, δ ppm): 163.5 (C]O), 145.3 (C]N), 111.7–151.3 (Aromatic carbon). (2,3-dimethoxybenzylidene)benzohydrazide found (C2): UV–Visible (λmax, nm): 255, 353; FT-IR (υ cm−1, KBr): 1560 (C]N), 1651 (C]O), 3023 (NH); 1H NMR(DMSO-d6, δ ppm): 11.5 (NH),

8.3 (N]CH), 3.8 (OCH3), 6.9–8.6 (Aromatic protons); 13C NMR (DMSO-d6, δ ppm): 164.3 (C]O), 144.3 (C]N), 55.7 & 61.6 (OCH3), 114.0–148.5 (Aromatic carbon). The antibacterial activities of synthesized hydrazones were evaluated by the agar well diffusion method. Muller Hinton agar medium (MHA) (20 mL) was poured into each petri plate and plates were swabbed with 100 μL inocula of the test microorganisms and kept for 15 min for adsorption. Using sterile cork borer of 8 mm diameter, wells were bored into the seeded agar plates and these were loaded with a 100 μL solution of each compound in dimethyl sulphoxide (DMSO) with concentration of 4.0 mg/mL. All the plates were incubated at 37 °C for 24 h. Antibacterial activity of each synthesized compounds were evaluated by measuring the zone of inhibition against the test organisms with zone reader. DMSO was used as a solvent, whereas Tetracycline was used as standard (Table 5). This procedure was performed in three replicate plates for each organism. MIC of the various synthesized hydrazones was tested against bacterial strains through a macro dilution tube method as recommended by NCCLS (Table 6).