Latent Role of Gallic Acid in the Antibacterial Potential of Fractions from the Commercially Available Rhizome of Calamus aromaticus

Background: The large scale growing and harvesting of Calamus aromaticus, a medicinally important weed, is rampant in Asia due to its well-known medicinal importance. The gigantic antimicrobial potential of C. aromaticus, however, is not reflected in the absolute sense by the efforts devoted to this purpose so far. Methods: The role of Gallic acid in the determination of antibacterial potency was established by first assessing the biological activity of different solvent extracted samples from the commercially available rhizome of C. aromaticus through disc diffusion assay. The different extracts were then quantified for the presence of Gallic acid using HPLC. Results: Staphylococcus aureus and Citrobacter freundii were more susceptible to crude methanol extract at 2000 μg.disc-1 (31.6% and 32.1% respectively) while Bacillus subtilis, Klebsiella pneumoniae, Pseudomonas aeruginosa, Escherichia coli and Xanthomonas campestris were more susceptible to ethyl acetate fraction at the same concentration (40.6%, 31.5%, 39.8%, 41.7% and 48.3% respectively). S. aureus was most susceptible gram positive bacterium and B. subtilis was comparatively more resistant. Among Gram negative bacteria, P. aeruginosa showed maximum susceptibility while K. pneumoniae revealed more resistivity in comparison to others. HPLC analysis of the extracts confirmed the hypothesis about the role of Gallic acid, with ethyl acetate fraction revealing the highest amount of the phenolic (12.6 mg.g-1). Conclusions: Organic solvents were found to be the solvents of choice for the extraction of Gallic acid and the results also pointed towards the potential of Gallic acid as a broad spectrum antibacterial agent.