Antibacterial, antioxidant activities and cytotoxicity of plants against Propionibacterium acnes

The use of plants to treat skin ailments has strong support in the current trend of drug discovery. Propionibacterium acnes, an anaerobic pathogen, plays an important role in the occurrence of acne. The present study was conducted to evaluate the antimicrobial and antioxidant activities against P. acnes and cytotoxic effects of 48 medicinal plants grown in South Africa. The broth dilution and DPPH radical scavenging methods were used to determine antibacterial and antioxidant activities, respectively. Cytotoxicity was determined on mouse melanocytes (B16-F10). The ethanolic bark extract of Acacia galpinii Burtt Davy. (Leguminosae) exhibited the lowest minimum inhibitory concentration of 62.5 μg/mL. Excellent antioxidant activity was shown by Aspalathus linearis (Burm.f.) R.Dahlgren (Leguminosae), Combretum apiculatum Sond. (Combretaceae), Harpephyllum caffrum Bernh. ex Krauss (Anacardiaceae) and Sclerocarya birrea Hochst. (Anacardiaceae), with 50% radical scavenging activity (EC50) at concentrations ranging from 1.6 μg/mL to 3.5 μg/mL. Greyia sutherlandii Hook. & Harv. (Greyiaceae) also exhibited good antioxidant activity with an EC50 value of 7.9±0.23 μg/mL. A. linearis, G. sutherlandii and S. birrea showed low toxicity with 50% viability of cells (EC50) at concentrations of 125.09±0.71 μg/mL, 107.85±1.53 μg/mL and 92.07±0.09 μg/mL, respectively. The extracts of A. linearis, G. sutherlandii and S. birrea showed good antibacterial and antioxidant activities and low toxicity. Therefore, these plants can be considered as possible anti-acne agents and warrant further investigation.