Microwave-assisted Synthesis, Characterization, Antimicrobial and Antioxidant Activities of 1-Benzyl-3-[(4-Methylphenyl)Imino]-Indolin-2-One and Its Co(II) Complex

Aims: To develop a simple, efficient microwave-assisted synthetic method to prepare 1-Benzyl-3-[(4-methylphenyl)imino]-indolin-2-one and its Co(II) complex, characterize and ascertain their biological significance.

Place and Duration of Study: School of Chemistry, Cardiff University, Wales, United Kingdom (November, 2007); Department of Chemistry & Industrial Chemistry, Department of Biological Sciences and Department of Biochemistry, Bowen University, Iwo, Nigeria (September 2015 and June 2018).

Methodology: N-benzylisatin and 4-methylaniline were microwave irradiated in acetic acid to give 1-Benzyl-3-[(4-methylphenyl)imino]-indolin-2-one (C22H18N2O, L; 58 %). L was microwave irradiated with CoCl2.6H2O in ethanol to yield its Co(II) complex. L was characterized using 1H-NMR, 13C-NMR, IR and Electronic spectra analyses, exact mass and melting point. IR and Electronic Spectra analyses with melting point confirmed the Co(II) complex was formed. The in-vitro antimicrobial activities of L were evaluated against three gram-positive bacteria (Staphylococcus aureus, Bacillus subtilis and Haemolytic Staphylococcus aureus), three gram-negative bacteria (Pseudomonas aeruginosa, Escherichia coli and Klebsiella sp.) and three fungi (Aspergillus niger, Trichoderma viride and Penicillium citrinum). The IC50 of L and its Co(II) complex were carried out against DPPH, H2O2 and NO radicals, as well as their reducing power abilities.

Results: Antimicrobial studies revealed L was active against Pseudomonas aeruginosa with a high zone of inhibition (thrice that of tetracycline) and Penicillium citrinum. The IC50 of L against DPPH, H2O2 and NO radicals were 0.561 ± 0.02, 0.3 ± 0.01 and 0.53 ± 0.01 μg/ml respectively, while they were 0.200 ± 0.01, 0.9 ± 0.02 and 0.26± 0.03 μg/ml for Co(II) complex. Their reducing power abilities at IC50 were 0.53 μg/ml (for L) and 0.6 ± 0.03 μg/ml (the complex).

Conclusion: L was synthesized within 15 min and its Co(II) complex within 5 min. L showed good free radical scavenging activities and reducing power when compared with ascorbic acid, while its Co(II) complex even performed better.