Comparative evaluation of the antimicrobial activities of essential oils of Artemisia afra, Pteronia incana and Rosmarinus officinalis on selected bacteria and yeast strains

Essential oils are frequently used for flavour and fragrance in the perfume, pharmaceutical, cosmetic and food industries. The antimicrobial activities of the essential oils of Artemisia afra, Pteronia incana and Rosmarinus officinalis were tested against 41 microbial strains. The test organisms were selected on the basis of their significance as food spoilage and/or poisoning, common human and plant pathogens. The agar diffusion assay was performed using nutrient agar and antibiotic medium. All the oils tested displayed some antimicrobial activities. However, the efficiency differed and depended both on the type and concentration of the oil, as well as the test microbial strain. Artemisia afra and R. officinalis showed similar and higher antimicrobial activity than P. incana. Due to their broad antimicrobial activities, the essential oils of the above plants growing in Eastern Cape may have preservative potential for the food and cosmetic industries.