Antibacterial potential of purple coneflower extracts and essential oils against some plant-related bacteria

Purple coneflower (Echinacea purpurea) have been always considered for its antimicrobial potentials. To evaluate the effect of coneflower methanol, ethanol, acetone, HCl and aqueous extracts and also flower essential oils, the bioassay and minimal bacteriostatic and bactericidal concentrations testes were carried out on some plant related bacteria including Pectobacterium atrosepticum, Pseudomonas fluorescens, Erwinia amylovora, Rhizobium tumefaciens, Bacillus subtilis and Rhodococcus faciens. Gentamycin® and dimethyl sulfoxide nutritive solvent were considered as positive and negative controls, respectively. For each bacterium, experiment was considered as completely randomized design with 24 treatments and three replications. Each bacterium reacted in different way against coneflower various organs extracts and flower essential oils. On the whole, coneflower essential oils were more inhibitive than extracts. In addition, Gr+ bacteria, especially R. faciens, did not get affected by coneflower extracts, however, essential oils were inhibitive, bacteriostatic and even bactericide. Antibacterials were accumulated in roots and flowers than leaves and stems. Acetone was the least effective solvent in antibacterials extractions. It seems coneflower has high potential for plant microbes’ biocontrol.