Assessment of antibacterial activity of smaller chain tripeptides and tetrapeptides

Our objective is to investigate the smaller chain tripeptides and tetrapeptides with the efforts mainly directed towards the identification of compounds presenting a high bactericidal activity. In this connection, 5 peptides, Met-Arg-Tyr (MRY), Met-Val-Tyr (MVY), Met-Ile-Cys-Tyr (MICY), Phe-Trp-Lys-Tyr (FWKY) and Met-Trp-Lys-Tyr (MWKY) were synthesized by solid phase peptide synthesis. The column eluted pure synthesized compounds were tested for in-vitro antibacterial disc diffusion assay using 2 g positive S. aureus, B.subtilis and 1 g negative E.coli bacterial strains at different concentrations predicted by pH and inhibitory concentration findings. 2 of the tetrapeptides, Phe-Trp-Lys-Tyr (FWKY) and Met-Trp-Lys-Tyr (MWKY) were found to be highly efficient against all the gram positive and microbial strains tested. Maximum activity was observed at a concentration of 300 µg/ml (499.17 µM) for the tetrapeptide Phe-Trp-Lys-Tyr (FWKY) against B. subtilis and at a concentration of 450 µg/ml (748.75 µM) against E. coli with the corresponding zonal inhibition diameter readings (17 mm; 16 mm). The tetrapeptide Met-Trp-Lys-Tyr (MWKY) was found to have high potency against S. aureus at a concentration of 450 µg/ml (769.23 µM) with the corresponding zonal inhibition diameter as 13 mm. The experimental results are analysed statistically by t-test at 5% and 1% level of significance. Our tetrapeptides have shown antibacterial action against both gram positive and gram negative strains and are considered safer as par with commercial antibiotics available today. Further clinical studies will make sure to position our potent small chain tetrapeptides in the arsenal of new broad spectrum anti-gram positive and anti-gram negative agent.