Antimicrobial activity of three medicinal plants against acne-inducing bacteria Propionibacterium acnes

Abstract

The antimicrobial activities of three medicinal plants (Senna alata L., Azadirachta indica A. Juss, and Aloe vera (L.) Burm.f.) against pimples causing bacterium Propionibacterium acnes was studied using disc diffusion method. Extracts from each plant were used on the bacterium at three different dosage concentrations (0.1 mL, 0.15 mL and 0.2 mL). Their Zone of inhibition was measured in millimeter (mm) and compared against a known synthetic standard (Gentamycin). Results indicate that the plants differ significantly in their activity against the studied microorganism. S. alata had the highest inhibitory effect of all the plants used (26.00 mm, 30.67 mm and 36.00 mm, for 0.1 mL, 0.15 mL and 0.2 mL dosage concentration, respectively). This was followed by A. indica with 9.33 mm, 15.67 mm and 16.67 mm zone of inhibition for 0.1 mL, 0.15 mL and 0.2 mL dosage concentration, respectively. A. vera had no effect (0.0 mm zone of inhibition) at 0.1 mL and 0.15 mL dosage concentrations, but at 2.0 mL dosage concentration, 4.0 mm zone of inhibition was achieved. Gentamycin showed zones of inhibition of 17.33 mm, 26.67 mm and 22.67 mm, for 0.1 mL, 0.15 mL and 0.2 mL dosage concentration, respectively. A comparison of all result obtained from the three plant extracts and gentamycin shows that S. alata have a significantly higher (p > 0.05) inhibitory effect against the pimples causing bacterium; Propionibacterium acnes than all the other treatments. The trend follows S. alata > Gentamycin > A. indica > A. vera, respectively, in terms of their inhibitory effect. Therefore, S. alata is more active and is the most appropriate plant to be used for treating of acne vulgaris among the three plant species selected for this experiment.