1292 Research Article Received: 2 November 2008 Revised: 1 March 2009 Accepted: 3 March 2009 Published online in Wiley Interscience: 21 April 2009 (www.interscience.wiley.com) DOI 10.1002/jsfa.3585 GC/MS analysis and antimicrobial and antioxidant activities of essential oil of Eucalyptus radiata Houcine Bendaoud, a Jalloul Bouajila, b∗ Ali Rhouma, c Arlette Savagnac d and Mehrez Romdhane a Abstract BACKGROUND: The essential oil from Eucalyptus radiata leaves collected in Tunisia was extracted by steam distillation and analysed by gas chromatography/flame ionisation detection and gas chromatography/mass spectrometry. Its antioxidant and antiradical properties were evaluated by the 1,1-diphenyl-2-picrylhydrazyl (DPPH) and 2,2 ′ -azinobis(3-ethylbenzothiazoline- 6-sulfonic acid) (ABTS) assays. The antimicrobial activity of the oil was examined in vitro against two plant-pathogenic bacteria (four strains each of Agrobacterium tumefaciens and Pseudomonas savastanoi pv. savastanoi) and two plant-pathogenic fungi (Fusarium solani and Rhizoctonia solani). RESULTS: Thirty-five compounds were identified and quantified in the essential oil, the major ones being 1,8-cineole (69.53%), α-pinene (11.94%) and trans-pinocarveol (4.81%). Medium antioxidant activity was found in the ABTS assay (IC 50 = 484.3 ± 17.3 mg L −1 ), whereas no significant free radical-scavenging activity was detected in the DPPH assay (IC 50 > 10 000 mg L −1 ). The antimicrobial assays showed that the oil exhibited a high level of activity against A. tumefaciens and R. solani, with minimum inhibitory concentrations ranging between 750 and 1000 μLL −1 . However, it was less efficient against P. savastanoi pv. savastanoi and F. solani. CONCLUSION: The results indicate that the essential oil of E. radiata, with a high content of terpenic compounds, exhibits significant antimicrobial activity against strains of A. tumefaciens and the fungus R. solani and may therefore be useful for their control. c  2009 Society of Chemical Industry Keywords: Eucalyptus radiata; essential oil; GC/MS; antimicrobial activity; DPPH; ABTS INTRODUCTION Plant pathogens are responsible for important losses in several economically important crops, in particular vegetables and fruits. 1 Although numerous research activities have been undertaken on the detection, molecular characterisation and epidemiology of bacterial diseases, their control is currently considered difficult. The only available methods used to control these bacteria are based on antibiotics and copper compounds. However, antibiotics are not allowed in agricultural practices in several countries because of the possible selection of resistant strains. 2 The use of copper compounds is also restricted and controlled in many countries because of their toxicity and, mainly, their impact on the environment. For the control of plant-pathogenic fungi, several fungicides are now available. However, synthetic fungicides are suspect in the food chain, and resistance by plant pathogens has rendered some of them ineffective. 3 Therefore alternative methods using new agents that are safe to humans and the environment are needed. These considerations emphasise the necessity for the develop- ment of new compounds for the control of plant bacterial diseases. Among these products, essential oils have been shown to have antimicrobial activities and could therefore serve as a source of antimicrobial agents against food and plant pathogens. 4 Essential oils are secondary plant metabolites found in leaves, stems, flowers and fruits. They frequently have different chemical composition depending on the nature of the plant and the season. The antimicrobial activity of the essential oil varies in the same plant owing to the effects of geographical site, harvesting season, ∗ Correspondence to: Jalloul Bouajila, Laboratoire de Synth` ese et de Physic- ochimie de Mol´ ecules d’Int´ erˆ et Biologique, UMR CNRS 5068, Universit´ e Paul-Sabatier, 118 Route de Narbonne, F-31062 Toulouse, France. E-mail: bouajila@cict.fr a Unit´ e de Recherche MACS, Ecole Nationale d’Ing´ enieurs de Gab` es, Route de M´ edenine, 6029 Gab` es, Tunisia b Laboratoire de Synth` ese et de Physicochimie de Mol´ ecules d’Int´ erˆ et Biologique, UMR CNRS 5068, Universit´ e Paul-Sabatier, 118 Route de Narbonne, F-31062 Toulouse, France c Unit´ e de Recherche Protection des Plantes Cultiv´ ees et Environnement, Institut de l’Olivier, Cit´ e Mahraj` ene, BP208, Tunis, Tunisia d UFR SVT, Universit´ e Paul-Sabatier, 118 Route de Narbonne, F-31062 Toulouse, France J Sci Food Agric 2009; 89: 1292–1297 www.soci.org c  2009 Society of Chemical Industry