Synthesis, characterization and antibacterial evaluation of some sulfonamide Schiff base derivatives

New series of Schiff base compounds obtained from sulfa drugs have been synthesized by the reaction of sulfonamide compounds (sulfadiazine, sulfapyridine, sulfamethazine, or sulfamerazine) with corresponding aromatic aldehydes (3-pyridinecarboxaldehyde or 4-pyridinecarboxaldehyde). The synthesized compounds were characterized by FT-IR, ESI-Mass, and 1H-NMR spectroscopy to confirm the chemical structures of synthesized compounds. The purity of all synthesized compounds were verified using pre-coated TLC (MERCK) plates using dichloromethane: methanol (9:1) solvent system. The chromatographic plates were viewed under ultraviolet(UV) light at 254 nm The sulfonamide Schiff base compounds were tested for antibacterial evaluation against two pathogenic Gram-positive bacteria (Staphylococcus aureus, Streptococcus spp.) and two pathogenic Gram-negative bacteria (Escherichia coli and Klebsiella pneumonia). The antibacterial activity of synthesized compounds was evaluated by assessing the inhibitory concentration by measuring their inhibition zone versus certain kinds of standard antibiotics with concentrations (500, 750, and 1000) μg /ml. Most synthesized compounds at high concentration were moderately active against all tested bacteria ,compound SH7 showed best antibacterial activity for both (Gram-positive and Gram-negative) bacteria while SH8 compound exhibited moderate antibacterial activity against Gram-positive bacteria and weak activity (<10 mm) against Gram-negative bacteria and all synthesized compounds were less antibacterial activity for all tested bacterial strains than standard drugs.