Chemical composition, antimicrobial activities and synergistic effects of essential oil from Senecio anteuphorbium, a Moroccan endemic plant

Over the past years, the emergence of multidrug-resistant pathogens has become a pressing public health problem. It is an important cause of morbidity and mortality worldwide and puts a considerably financial burden on the health care system. The development of new antimicrobials is becoming increasingly difficult, time-consuming and expensive. Hence, new approaches are urgently needed to replenish our arsenal of antimicrobial agents. Plant tissues contain a wild variety of antimicrobial constituents discovered and used to reverse drugs resistance and restore their efficiency. For this, essential oil (EO) extracted from aerial parts of Senecio anteuphorbium (L) Haw, a Moroccan endemic plant, was studied for the first time for its: (i) Qualitative and quantitative chemical profile, (ii) antimicrobial activities, (iii) and synergistic interactions with two conventional antifungals and ciprofloxacin. The data of the chemical composition showed that S. anteuphorbium EO was characterized by the abundance of γ-selinene (27.2%), cyperene (21.7%), γ-cadinene (11.4%) and α-cyperone (8.1%). Regarding antimicrobial assays, results demonstrated that S. anteuphorbium EO displayed moderate antimicrobial activities with MIC values in the range of 0.51 mg/mL and 1.02 mg/mL for yeasts and between 2.3 mg/mL and 4.6 mg/mL for bacteria. However, the combination of the studied EO with fluconazole and ciprofloxacin showed a significant decrease in their individual MICs. In fact, at sub-inhibitory concentrations S. anteuophorbium EO contributed to the decrease of fluconazole MICs of Candida strains by 4- to 64- fold and by 2- to 16- fold regarding ciprofloxacin MICs. The overall data suggest that the topical or systemic use of S. anteuphorbium EO in combinational treatments may be a promising strategy to combat infectious diseases and further studies should be performed in order to well determine the main mechanism of these synergistic associations.