Comparative Study on the Antibacterial Activity of Four Medicinal Plants Leaves of Different Ages (original) (raw)

Plants are the richest source of natural antimicrobial agents. The present study was carried out to evaluate the antibacterial effect of four important plants namely, Rauvolfia serpentina, Tagetes erecta, Brassica nigra, Ocimum tenuiflorum. Powdered leaf materials of all selected plants were extracted with methanol. The solvent extracts were evaporated for dryness using rotary evaporator. Dry residue was dissolved in methanol (1:10 w/v) and different volume of tested sample is applied for antibacterial activity. The antibacterial screening of the selected crude methanolic extracts were determined according to Kirby-Bauer's Disc diffusion method on the following bacteria-Staphylococcus aureus, Salmonella typhi, Escherichia coli, Pseudomonas aeruginosa. The experiment showed that R. serpentina exhibited excellent antibacterial activity against tested bacterial organisms as compared to the standard Norfloxacin. Maximum of 21.60 ±0.40 mm zone of inhibition was recorded against gram positive bacteria S. aureus for the leaves aged >30 days (100µl) of R. serpentine and maximum of 18.90 ±0.84 mm was recorded for the leaves of T. erectra aged >30 days (100µg), whereas the least inhibitory zone was found 7.80± 0.45 mm for the leaves aged 5-15 days (15 µl). Again, maximum zone of inhibition 28.12±0.40 mm was found for the positive control, Norfloxacin. This result revealed that due to the increases of ages, antimicrobial activities of leaves also increases. S. typhi showed no sensitivity for any of the tested plant leaves extracts, whereas other gram-negative bacteria showed some degree of susceptibility. E. coli showed excellent susceptibility against R. serpentina. P.aeruginosa showed susceptibility against O.tenuiflorum. Although, it is resistant against the other leaves extracts. B. nigra didn't show any antimicrobial activity. Our results demonstrated that methanol extracts of these plants leaves have age and concentration dependent antibacterial activity against some of the tested organisms. Further studies should be undertaken to elucidate the exact mechanism of action of antimicrobial effect to identify the active ingredients which can be used in drug development program.

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