Please cite this article in press as: Stefanaki, A., et al., The Oregano plants of Chios Island (Greece): Essential oils of Origanum onites L. growing wild in different habitats. Ind. Crops Prod. (2015), http://dx.doi.org/10.1016/j.indcrop.2015.11.086 ARTICLE IN PRESS G Model INDCRO-8566; No. of Pages 7 Industrial Crops and Products xxx (2015) xxx–xxx Contents lists available at ScienceDirect Industrial Crops and Products journal homepage: www.elsevier.com/locate/indcrop The Oregano plants of Chios Island (Greece): Essential oils of Origanum onites L. growing wild in different habitats Anastasia Stefanaki a,∗ , Catherine M. Cook b , Thomas Lanaras c , Stella Kokkini a a Laboratory of Systematic Botany and Phytogeography, School of Biology, Aristotle University of Thessaloniki, 541 24 Thessaloniki, Greece b Hellenic Agricultural Organisation “Demeter”, General Directive of Agricultural Research, Institute of Plant Breeding and Phytogenetic Resources, P.O. Box 60458, GR-570 01 Thermi, Greece c Department of Botany, School of Biology, Aristotle University of Thessaloniki, 541 24 Thessaloniki, Greece a r t i c l e i n f o Article history: Received 14 July 2015 Received in revised form 24 November 2015 Accepted 30 November 2015 Available online xxx Keywords: Lamiaceae Essential oils Carvacrol Origanum onites Habitat type Origanum vulgare subsp. hirtum a b s t r a c t Oregano herbs have wide culinary uses and industrial applications due to the high antioxidant and other activity of their main essential oil compound, carvacrol. Among the oregano herbs, Ori- ganum onites (known as “Turkish oregano”, “Island oregano” or “Cretan oregano”) is a narrowly distributed East Mediterranean species occurring mainly in Turkey and Greece, which comprises one of the major herbs of the oregano trade worldwide. We examine the essential oils of O. onites plants collected from 42 localities scattered along the total range of the species on Chios, a Greek island bordering with the Turkish mainland. We focus on the essential oil yield and five oil compounds, namely carvacrol, thymol, borneol and the biosynthetic precursors of the first two, i.e., p-cymene and -terpinene, in relation to the habitat type, geological substrate, altitude, bioclimatic area and geographical location, where the collected plants were growing on the island. We also discuss our results in relation to the essential oil based distinction between O. onites and another com- mercially important East Mediterranean oregano herb, namely Origanum vulgare subsp. hirtum (known as “Greek oregano”). The determined essential oil yield (3.0–7.0 mL/100 g of dry leaves and inflorescences) and carvacrol content (69.0–92.6%) of the examined O. onites plants from Chios are among the highest reported for this species. The essential oil yield and the content of the five compounds were not found to vary in relation to the different environmental factors examined. These findings let us conclude that the wild oregano of Chios is a valuable natural resource with a high potential for industrial use, due to its high essential oil yield and carvacrol content, that are not influenced by environmental conditions. Moreover, based on our results and recent literature we conclude that O. onites can be distinguished from O. vulgare subsp. hirtum based on the relative content of carvacrol, thymol, borneol and p-cymene – primarily borneol – in the two taxa’s essential oils, a useful means of distinction when the botanical identity of fragmented commercial oregano products is questioned. © 2015 Elsevier B.V. All rights reserved. 1. Introduction The name “oregano”, attributed to several plant taxa of different families and genera, corresponds to the characteristic odor origi- nating from the high amounts of the phenol carvacrol in these taxa’s essential oils (Kokkini et al., 2003; Lawrence, 1984). Apart from their established culinary use as food flavorings, oregano herbs ∗ Corresponding author. E-mail address: anastasia.stefanaki@gmail.com (A. Stefanaki). have applications in the pharmaceutical and food industry due to the antioxidant, antimicrobial, antimycotic, insecticidal and other activities of their essential oil resulting from their phenolic content, primarily carvacrol (Baser, 2008; Burt, 2004; Kokkini et al., 2003; Zheng and Wang, 2001). Known and used for centuries, oregano has gained popularity in the last decades, with its worldwide pro- duction reaching about 10000 t (Kintzios, 2002). As is the case with many aromatic plants, a substantial amount of the traded oregano herbs is derived from the wild and is often sold in a fragmented (crushed or even ground) form (Kintzios, 2002). Thus the quality of an oregano product may vary depending on the http://dx.doi.org/10.1016/j.indcrop.2015.11.086 0926-6690/© 2015 Elsevier B.V. All rights reserved.