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Eur J Clin Microbiol Infect Dis (2012) 31:10151025 DOI 10.1007/s10096-011-1400-1
ARTICLE
Antistaphylococcal activity of Inula helenium L. root essential oil: eudesmane sesquiterpene lactones induce cell membrane damage
Z. Stojanovi-Radi & Lj. omi & N. Radulovi &
P. Blagojevi & M. Deni & A. Miltojevi & J. Rajkovi &
T. Mihajilov-Krstev
Received: 6 July 2011 /Accepted: 17 August 2011 /Published online: 8 September 2011 # Springer-Verlag 2011
Abstract The purpose of this study was to investigate the inhibitory/bactericidal activity and cell membrane effects of the hydrodistilled essential oil of Inula helenium L. roots against Staphylococcus aureus. Additionally, detailed chemical investigation was done in order to pinpoint the most active oil constituents and also the parts of these molecules responsible for their antimicrobial effect. The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) were determined using the broth microdilution method. The membrane-active nature of this oil was investigated by measuring the culture turbidity, leakage of phosphates, and 260-nm-absorbing material, together with lysis of the exposed cells. Finally, the effect of the oil on the cells was visualized using scanning electron microscopy (SEM). The chemical composition of the essential oil was
analyzed using gas chromatography-mass spectrometry (GCMS) and preparative medium-pressure liquid chromatography (MPLC). Chemical modification of the oil was performed using catalytic hydrogenation (H2, Pd/C) and reduction with
NaBH4. The MIC and MBC values were 0.01 l mL1 and0.02 l mL1, respectively. Membrane damage was demonstrated through increased permeability (phosphates and nucleic acid leakage), followed by lysis of the exposed cells, captured on SEM images. The most active constituents were alantolactone, isoalantolactone, and diplophyllin. The essential oil showed very potent antistaphylococcal activity, with obvious membrane-damaging effects. Sesquiterpene lactones were found to be the most active principles of the oil, whose eudesmane core olefinic bonds, along with the ,-methylene-lactone ring, are essential structural parts responsible for the exhibited antimicrobial activity.
Introduction
Inula helenium L. (elecampane inula, oman in Serbian), family Compositae, is a perennial plant species native to Europe and East Asia. In Serbia, it is a widespread plant, used in folk medicine mostly for the treatment of respiratory conditions such as asthma, bronchitis and whooping cough, disorders of digestion, urinary infections, and also for skin disorders. Although only a limited number of studies deals with the antimicrobial...