Soumis le : 03/11/2016 Nature & Technology http://www.univ-chlef.dz/revuenatec Forme révisée acceptée le : 25/10/2017 Auteur correspondant : tolba.hadjer@hotmail.fr Essential oil of Algerian Eucalyptus citriodora: Chemical composition, antioxidant and antimicrobial activities TOLBA Hadjer a,* , MOGHRANI Houria a , ABOUN Assia b , MAACHI Rachida a a Laboratoire de Génie de la Réaction, Faculté de Génie mécanique et Génie des procédés, USTHB, BP 32 El Alia, 16075 Bab Ezzouar, Alger, Algérie. b laboratoire de bactériologie et Sérologie Vétérinaire, Institut Pasteur, Kouba, Alger, Algérie Abstract This study was carried out to assess the chemical composition, antioxidant and antimicrobial activities of Eucalyptus citriodora essential oil growing in Algeria. The chemical composition of the oil was analyzed by GC and GC/MS and revealed the presence of 22 compounds which accounted for 97.13 % of the oil. The main compounds was Citronellal (69.77 %) followed by Citronellol (10.63 %) and Isopulegol (4.66 %). Antioxidant activity was evaluated by using 1,1-diphenyl-2-picrylhydrazyl (DPPH) assay. The free radical scavenging activity of the oil was found to be inferior (IC 50 values = 0.896 mg/ml) as compared to butylatedhydreoxytoluene (BHT), (IC 50 value = 0.041 mg/ml). The antimicrobial activity of Eucalyptus citriodora essential oil against twelve bacteria and two yeasts was determined via both the disc diffusion method and the Disc volatilization method. Higher antimicrobial activity was observed in the liquid phase. The minimum inhibitory concentration (MIC) was found to vary from 0.6 to 20 μl/ml for bacteria while for yeasts it was equal to 1.25 μl/ml. The most sensitive strains were the Gram positive bacteria Staphylococcus epidermidis and the two yeasts while the most resistant bacterium was Pseudonomas aeruginosa. This is the first report on the antioxidant and antimicrobial properties of the essential oil of Eucalyptus citriodora growing in Algeria. Keywords: Antimicrobial activity; Antioxidant activity; Chemical composition; Essential oil; Eucalyptus citriodora Hook. 1. Introduction Aromatic plants, such as those from Myrtaceae family are known for their wide spread use both traditionally and commercially to increase the shelf-life and safety of foods. They have demonstrated several therapeutic properties, mainly antioxidant, antimicrobial and anti- inflammatory. This usefulness of plants is due to their complex mixture of compounds including aldehyde, and phenolic compounds [1]. In particular, the antimicrobial properties of plant essential oils and their constituents have been widely demonstrated [2]. Eucalyptus, a native from Australia, belongs to Myrtaceae family and includes about 800-900 species and subspecies [3, 4]. Today, Eucalyptus may be found almost everywhere in the world since it is grown in many countries [5] including tropical, subtropical and even sub-temperature countries [6]. Aromatic plants and their essential oils have been used since antiquity in flavor, fragrance, embalmment, preservation of foods, antimicrobial remedies, medecine, perfumery, and pharmaceutical industries [7, 8]. Eucalyptus has been largely studied as a source of essential oil, extracted through steam or hydrodistillation, which has diverse biological activities. Several works have focused on the functional aspects of Eucalyptus essential oil, such as antimicrobial, antifungal, insecticidal, and acaricidal activities [7]. The antimicrobial effects against a wide range of microorganisms have been considered in several studies. The most often considered species include Eucalyptus globulus [9], Eucalyptus camaldulensis, Eucalyptus terticornis, and Eucalyptus citriodora [3, 10, 11]. In the present work, we focused on Eucalyptus citriodora, which is one species of eucalyptus widely used in perfumery, and as an important ingredient of cosmetics, food and pharmaceutics. Its essential oil exhibits various biological properties. These effects are attributed to the monoterpenes, which are the major chemical components of this essential oil. Eucalyptus citriodora has been shown to contain about 70 % of monoterpenoid, Citronellal, which is a monoterpene product from the plant secondary metabolism. different studies have demonstrated that Eucalyptus citriodora essential oil possesses a wide spectrum of biological activities including antimicrobial