Abstract
Three Schiff bases L1, L2 and L3 were synthesized by condensing salicylaldehyde with 4-aminoantipyrine, ethylendiamine and 2-aminophenol respectively and subsequently characterized by various physicochemical investigations. All the three compounds were screened for their In-vitro antibacterial activity against two gram positive bacteria, Staphylococcus aureus (S.A), Staphylococcus epidermidis (S.E) and two gram negative bacteria Klebsiella pneumoniae (K.P) and Pseudomonas aeruginosa (P.A) by agar diffusion method. On comparing the results obtained with the activity of commercially available antibiotics such as Ciprofloxacin and Chloramphenicol, the newly synthesized compounds showed comparable antibacterial activities. The solvent methanol exhibit activity against all bacterial species with IZs ranging from 8 ± 0.25 to 17 ± 0.29 mm while the standard antibiotics Ciprofloxacin and Chloramphenicol exhibited an activities with IZs varying from 21.3 ± 0.31 to 28.3 ± 0.32 and 26.3 ± 0.24 mm to 32.3 ± 0.23 mm, respectively. However, the newly synthesized Schiff bases L1, L2 and L3 showed IZs ranging from 7.4 ± 0.23 to 32.5 ± 0.14, 3 ± 0.57 to 12 ± 0.28 and 10 ± 0.20 to 32 ± 0.36 respectively. Among the Schiff bases, L3 showed the activity (32 ± 0.36) against S.E and P.A which is higher than the activity of standard antibiotics Ciprofloxacin and Chloramphenicol against the same bacterial strains. The results obtained revealed that all the synthesized Schiff bases exhibit appreciable antibacterial activity against all the bacteria species which potentially makes them, to apply as wide range antibacterial drugs, after further in-vivo cytotoxicity investigations. Their activity can also be further modified by changing the functionality of precursors for Schiff base condensation.
Highlights
Schiff bases are the class of compounds, which are obtained by condensing primary amines and carbonyl compounds [1]
The peak observed at 1425 cm−1 corresponds to N-CH3 stretching vibration while the aromatic νC-H asymmetric and symmetric stretching bands are observed at 3085 cm−1 and 3075 cm−1 respectively
The antibacterial activities of these compounds were examined using different cultures of bacteria and the results revealed that all the Schiff bases of current study showed appreciable activity
Summary
Schiff bases are the class of compounds, which are obtained by condensing primary amines and carbonyl compounds [1]. They are known as an imine or azomethine, is an analogue of a ketone or aldehyde in which the carbonyl group (-C=O) is changed to imine or azomethine (-HC=N-) functionality on reacting with a primary amine (Scheme 1). Since the discovery of Schiff base [2], it has drawn much attention due to the easy tailoring possibility of the compounds by incorporating different substituents in both amino and aldehydic precursors, which may bring about the variation in the fundamental properties of the synthesized products. Increasing importance of Schiff bases as biochemical and analytical reagents are well documented [8]
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