Antimicrobial potential of lemon and onion extracts against gram-positive and -negative bacteria

Abstract

Antimicrobial potentials have been widely analyzed with different sources; however, plant-based antimicrobial compounds are greatly welcome due to their greener characteristics. This study revealed the importance of antimicrobial compounds from the herbal extracts of lemon and onion. The extracts were tested against gram-negative (Escherichia coli) and gram-positive (Bacillus subtitlis) bacteria. Disc-diffusion and well-diffusion on an agar plate and tributary methods were followed to demonstrate the antimicrobial potentials of the above herbal extracts. Further, different volumes of ampicillin at the concentration of 1 mg/ml were used to compare the genuine bacterial inhibition (3 µL with 1.5 cm zone). Lemon behaved excellently in a way by displaying better bacterial inhibition against both E. coli (3 µL with 1.2 cm zone) and B. Subtilis (3 µL with 0.6 cm zone), whereas onion extract was not at the level of lemon extract; however, it still displayed a good inhibition. The turbidity assay confirms the inhibition efficiency of lemon and onion against both E. coli and B. subtilis. In the liquid medium lemon shows higher inhibition (2 & 3 folds) on bacteria than that of ampicillin and onion. Cell count and UV-vis spectroscopy analysis at 600 nm also conform to the efficacy of lemon inhibition against E. coli and B. subtilis. This experiment confirms that lemon extract is an excellent and better substitute for commercially available ampicillin for bacterial inhibition.