Green Synthesis and Antibacterial Activity of a 3-Nitroaniline-3-Nitrobenzaldehyde Schiff Base

Abstract

3-nitroaniline and 3-nitrobenzaldehyde were refluxed in ethanol for 2 hours in an acidic medium to afford pale-yellow crystals of a Schiff base at 58% yield. The melting point and retention factor (Rf) of the product were checked, giving a value of 151 – 152°C and 0.54 respectively. The IR spectrum showed the following bands (cm-1); 1637 (imino, C=N), 1577 (Aromatic C=C stretch), 3074 and 3096 (Aromatic C – H stretch), 1346 and 1525 (Aromatic NO2 stretch) and 896 (Aromatic NO2 scissors). In addition, the 1HNMR spectrum showed a singlet at 8.44 ppm which represented the 1 H of the imino group, and a 8H multiplet between 7.18 – 8.41 ppm representing the aromatic protons. Furthermore, an antibacterial screening was done using the Schiff base on four (4) bacteria strains; Pseudomonas aeruginosa, Staphylococcus aureus, Serratia marcescens, and Escherichia coli. The result from the screening portrayed that the highest zone of inhibition (ZOI) recorded for all bacteria was at a concentration of 200 mg/ml of the test compound, while the lowest was at a concentration of 50 mg/ml. This gave a ZOI of 12 mm, 10 mm, 13 mm, and 11mm for P. aureginosa, S. aureus, S. marcescens, and E. coli respectively. The results generally showed an increase in ZOI with increased concentration of the product. The best result observed was that obtained for S. marcescens which showed ZOIs of 7 mm, 10 mm, 12 mm, and 13 mm for concentrations of 50, 100, 150, and 200 mg/ml respectively.