Synthesis, characterization and biological properties of new imines derived 5-nitroisatin

5-Nitroisatin and thiocarbohydrazide were mixed under reflux for 5 hours in the presence of ethyl alcohol in the presence of two drops of HCl to obtain 5-nitroisatin–β–thiocarbohydrazide. This synthesized compound was reacted with benzaldehyde and its derivatives to obtain corresponding 9 different imine compounds in 55–93% yield. The structures of these compounds were elucidated by FT-IR, 1H NMR, 13C NMR spectroscopic techniques and elemental analysis method. Physicochemical properties of the synthesized compounds such as solubility, color and melting point were determined. Antimicrobial activities of the synthesized compounds were investigated against various strains. Three Gram positive starins (Bacillus subtilis ATCC 6623, Staphylococcus aureus ATCC 25923, Enterococcus faecalis ATCC 29212), three Gram negative strains (Escherichia coli ATCC 25922, Klebsiella pneumoniae ATCC 70060, Pseudomonas aeruginosa) and two different fungi (Candida albicans ATCC 10231, Aspergillus niger ATCC 16404). As a result of the obtained data, it was determined that compound 7 has excellent antibacterial activity against both gram-positive and gram-negative strains. Among the synthesized structures, compound 7 (N'-(4-hydroxy-3,5-dimethoxybenzylidene)-2-((Z)-5-nitro-2-oxoindolin-3-ylidene)hydrazine-1-thiocarbohydrazide, MIC: 64 µg/mL) exhibited better antibacterial activity than Amoxicillin (MIC: >1024 µg/mL), one of the standard drugs used against the E. faecalis pathogen, while it showed the same activity as Tetracycline. All compounds showed better antibacterial activity than the Amoxicillin standard, except for compound 1 (N'-benzylidene-2-((Z)-5-nitro-2-oxoindolin-3-ylidene)hydrazine-1-thiocarbohydrazide). The in vitro total antioxidant activity determinations were made with phosphomolybdenum method. Total antioxidant activity were followed by the order of 3 > compound 5 > BHT > compound 4 > compound 8 > compound 7 > compound 2 > compound 6 > Troloks > compound 9 > compound 1. Compounds 3 and 5 showed better total antioxidant activity than standard both BHT and Troloks.