Investigation on antimicrobial effects of essential oil of purple coneflower (Echinacea purpurea L.) and identification of its chemical compounds

Purple coneflower (Echinaceae purpurea L.) is a perennial herbaceous with astringent properties، disinfectant، antimicrobial and anti intoxication activity. The main objective of this study was to evaluate the antimicrobial activity of shoot essential oil of purple coneflower against some microorganisms including gram positive، gram negative bacteria، filamentous fungi and yeasts.

In this experimental and laboratory investigation، plant samples were collected in full blooming stage. Shoot essential oil was extracted by hydro-distillation technique using Clevenger apparatus. The chemical constitutes of this oil was analyzed by GC and GC/MS method. Anti microbial properties of the essential oil were determined using micro broth dilution and well disk diffusion methods. At the end، data were analyzed by the SPSS version 15 software، using the T-test and Duncan s'' test.

Twenty nine components were identified by GC and GC/MS in the essential oil of purple coneflower representing 96. 21% of total oil. The major components were Germacrene D (53. 30%)، -Cymene (9. 78%)، β-Caryophyllene (7. 52%)، α-Humulene (5. 22%)، β-Bisabolene (4. 43%) and α-Pinene (4. 23%)، respectively. This oil exhibited strong antifungal activity against filamentous fungi and yeast with average of inhibition zone (AIZ) 39. 63. Microorganisms differ in their resistance to purple coneflower oil. All of the bacteria including gram positive and gram negative bacteria are more resistant than fungi; and gram negative bacteria are more resistant than gram positive bacteria. Pseudomonas aeruginosa and Salmonella typhimurium were more resistant than others.

The results of this study showed that coneflower essential oil with significant antimicrobial effects and can be used instead of synthetic antibiotics that microbial resistance towards them is increasing.