The essential oil of Senecio graveolens ( Compositae): chemical composition and antimicrobial activity tests

The chemical composition of the essential oil obtained from Senecio graveolens ( Compositae) was analyzed by GLC–MS and the components identified were: isovaleraldehyde, α-pinene, α-phellandrene, α-terpinene, p-cymene, sabinene, γ-terpinene, 1-methyl-4-isopropenylbenzene, terpinolene, terpinen-4-ol, piperitenone, α- and β-eudesmol. The investigation by the agar-well diffusion method of the antimicrobial activity of the essential oil proved that it has antibacterial effects on Micrococcus luteus ATCC 9341, oxacillin-sensitive and oxacillin-resistant Staphylococcus aureus, as well as antifungal effects on clinically isolated Candida albicans. The minimal inhibitory concentration (MIC) values for M. luteus, oxacillin-sensitive S. aureus and C. albicans were 8.73, 10.91 and 2.13×10 −2 mg/ml, respectively. The antimicrobial activity related to known antibiotics was calculated. These results would be compatible with a potential concentration-dependent selectivity of antifungal effect of S. graveolens essential oil. Minimal bactericidal concentration (MBC) is above 87.3 mg/ml. Thus the MBC/MIC ratio would be clearly higher than 1 (above 8), indicating a bacteriostatic effect of the essential oil.