Assessment of in vitro antioxidant activity of essential oil of Eucalyptus citriodora (lemon-scented Eucalypt; Myrtaceae) and its major constituents Harminder Pal Singh a, * , Shalinder Kaur a , Kirti Negi a , Savita Kumari b , Varinder Saini a , Daizy R. Batish b , Ravinder Kumar Kohli b a Department of Environment Studies, Panjab University, Chandigarh 160014, India b Department of Botany, Panjab University, Chandigarh 160014, India article info Article history: Received 12 October 2011 Received in revised form 17 March 2012 Accepted 21 March 2012 Keywords: Eucalyptus citriodora Total antioxidant activity DPPH scavenging Inhibition of lipid peroxidation Hydrogen peroxide scavenging abstract We investigated the chemical composition and antioxidant activity of Eucalyptus citriodora (lemon- scented eucalyptus) leaf oil in terms of total antioxidant activity, ferric reducing antioxidant power (FRAP) assay, ferrous ion chelating activity, and scavenging of hydrogen peroxide (H 2 O 2 ) and 2,2- diphenyl-1-picrylhydrazyl (DPPH  ) radicals and inhibition of lipid peroxidation. GCeMS analysis of essential oil revealed the presence of 43 components constituting 99.2% of oil. The oil was mono- terpenoid (94.35% of oil) with citronellal (60.66%), b-citronellol (12.58%) and isopulegol (8.19%) as the major monoterpenoids. Oil and its major monoterpenes exhibited moderate to strong antioxidant activity in terms of TAA, FRAP and Fe þ2 chelating, DPPH  and H 2 O 2 scavenging, and lipid peroxidation inhibition. The study concludes that E. citriodora leaves contain monoterpenoid rich oil exhibiting antioxidant activity. Ó 2012 Elsevier Ltd. All rights reserved. 1. Introduction Eucalyptus is a large genus of family Myrtaceae comprised of about 900 species and subspecies (Brooker & Kleinig, 2004). Though it is a native of Australia, it is found in almost all parts of the world due to human introduction. It is now cultivated in many tropical, sub-tropical and even sub-temperate countries (Batish, Singh, Kohli, & Kaur, 2008). Eucalyptus is generally grown for its wood, which is primarily used in making cellulose pulp and secondly for boards and panels (Brooker & Kleinig, 2004). Euca- lyptus species are well-known for their essential oils that are extracted through steam or hydrodistillation. These have been widely used in the perfumery and fragrance industries, and in fact, these are among the world’s top-traded oils (Batish et al., 2008). Essential oil from Eucalyptus species has been used as an antiseptic, antipyretic and analgesic since ancient times (Brooker & Kleinig, 2004). It has been reported to possess a wide range of biological activities including antimicrobial, fungicidal, insect-repellant, fumigant, pesticidal and acaricidal activity (Batish et al., 2008). Free radicals have deleterious effects on the human body and cause oxidative damage to proteins, carbohydrates, lipids, enzymes, and DNA (Halliwell & Gutteridge, 1989). Living cells possess an excellent scavenging mechanism to avoid free radical-induced injury; however, under the influence of external stresses these mechanisms become inefficient. Therefore, food stuffs are supple- mented with synthetic antioxidants like butylated hydroxytoluene (BHT) and butylated hydroxyanisole (BHA). However, due to toxi- cological concerns linked to their use over a long period and increasing awareness about natural foods, there has been a renewed interest in the use of natural substances as antioxidants (Babich, 1982). In this context, essential oils and their components due to their relatively non-toxic nature, acceptance with consumers, and a wide spectrum of biological activity, have gained much attention as a potential source of antioxidants (Batish et al., 2008). Among essential oils, eucalyptus oils hold a good promise. These have been placed under the GRAS (Generally Regarded as Safe) category by the Food and Drug Authority (FDA) of the USA and classified as non-toxic (USEPA, 1993) and approved as flavoring agent in food (5 mg/kg) and confectionery items (15 mg/kg) in Europe (Council of Europe, 1992). It is therefore worthwhile to evaluate the essential oils from the eucalyptus species for their antioxidant activity with a view of their pharmaceutical application. Eucalyptus citriodora is one species of eucalyptus widely used in perfumery, for cleaning air, and as an important ingredient of cosmetics and room fresheners. Earlier studies have demonstrated that essential oil from E. citriodora possesses antibacterial, anti- fungal, anticandidal, insecticidal, acaricidal, antitrypanosomal and * Corresponding author. Tel.: þ91 172 253 4095. E-mail addresses: hpsingh_01@yahoo.com, hpsingh_01@pu.ac.in (H.P. Singh). Contents lists available at SciVerse ScienceDirect LWT - Food Science and Technology journal homepage: www.elsevier.com/locate/lwt 0023-6438/$ e see front matter Ó 2012 Elsevier Ltd. All rights reserved. doi:10.1016/j.lwt.2012.03.019 LWT - Food Science and Technology 48 (2012) 237e241