Essential Oil Composition of Greek (Origanum vulgare ssp. hirtum) and Turkish (O. onites) Oregano: a Tool for Their Distinction
Aiming to find out if any distinction between the Greek (Origanum vulgare ssp. hirtum) and Turkish oregano (O. onites) essential oils exists, the composition of six wild Greek populations of the former and four of the latter taxon were analyzed by means of GC and GC/MS. A PCA analysis showed that Turkish oregano oils had higher amounts of sabinene, myrcene, [gamma]-terpinene, borneol and carvacrol, and Greek oregano oils had higher p-cymene content. The latter were further divided into two subgroups, distinguished respectively by their thymol and carvacrol content. A comparison of our results with the published information showed that p-cymene percentages > 14% and/or thymol > 6% is found only in Greek oregano, while borneol content > 2% is found only in Turkish oregano oils.
Key Word Index
Origanum vulgare ssp. hirtum, Origanum onites, Lamiaceae, Greek oregano, Turkish oregano, essential oil composition, p-cymene, borneol, thymol, carvacrol.
The commercial name Oregano’ refers to a number of species that produce essential oils with a characteristic smell due to the high concentration of carvacrol (1). Among the most popular oregano spices are the commercially known as Greek oregano [Origanum vulgare L. ssp. hirtum (Link) letswaart] and Turkish oregano (O. onites L.). Origanum vulgare ssp. hirtum (section Origanum) occurs mainly in the Balkan Peninsula, Turkey andCyprus,betweenseaIevelandl,500m(2) (Figure 1). Origanum onites [section Majorana (Miller) Bentham] has a rather narrow distribution, restricted in Greece and in west and south Turkey; it grows at altitudes between sea level and 1,400 m (3) (Figure 1). It is reported that the essential oils of the two taxa have antimicrobial (4,5-6), antioxidant (7-8), antifungal (9), cytotoxic (6), insecticidal (10) and nematicidal activities (11).
A large part of the commercially available oregano still derives from the wild growing O. vulgare ssp. hirtum and O. onites populations of East Mediterranean (12). As they are usually finely fragmented when trading, their botanical source is difficult to be determined. The present work is a comparative study of the essential oils of Greek and Turkish oregano. In an attempt to find out if the oil composition can be used for the distinction of the two oregano taxa, our results are further discussed in relation to the literature data.
Plant material: Aerial parts of O, vulgare ssp. hirtum and O. onites plants were collected during late autumn, from three distinct geographic areas of Greece (Figure 1). Origanum vulgare ssp. hirtum: Athos Peninsula: (1) NE of the town of Karyes, 350 m; (2) S of the town of Karyes, 270 m; (3) Town of Karyes, 500 m. Peloponnese: (4) SW of the city of Gythion, s.l. Island of Crete: (5) S of the village Perivolia, 130 m; (6) Village Meskla, 170 m. Origanum onites: Peloponnese: (7) Near the village ToIo, s.l.; (8) Near the village Skala, 100 m. Island of Crete: (9) Near the village Prasies, 330 m; (10) Near the village Eleftherna, 400 m.
The plants were collected during the post-flowering stage. Voucher specimens were deposited in the Herbarium of the Institute of Systematic Botany and Phytogeography, Aristotle University of Thessaloniki (TAU).
Essential oil isolation: The collected plant material was air-dried at room temperature for 10 days. Then it was grossly pulverized and subjected to hydrodistillation for 2 h using a Clevenger-type apparatus. The oil content was estimated on a dried plant material basis.
Oil analyses: The oils, thus isolated, were chromatographed using a Shimadzu GC-14A gas chromatograph equipped with a Supelcowax 10 capillary column (60 m × 0.25 mm). Injector and detector temperatures were 240°C. The carrier gas was helium with a flow rate 20.4 cm/s (0.6 mL/ min). The column temperature program adopted was: 70°C for 10 min, 70°-180°C at 2°C/min, isothermal for 35 min, then from 180°-200°C at 4°C/min, and finally at 200°C for 5 min. Data were recorded on a Shimadzu CR-4AX integrator and analysed using CLASS-UniPac (Shimadzu) software.
GC/M S analyses of the oils were carried out in a Shimadzu GC-MS QP2000 system (quadropolar system with an ionization energy of 70 eV). The same column and running conditions (temperature program and carrier gas) as in the GC analysis were used. The oil components were identified comparing their relative retention times and mass spectra with those of authentic samples, the Wiley Registry of Mass Spectral Data (13) and published data (14-15) using Benchtop/ PBM Version 3.1 (Palisade Corporation) software.
Statistical analysis: Principal component analysis (PCA) (16) was applied to examine the interrelationships between the studied oils using the following variables: sabinene, myrcene, [gamma]-terpinene, p-cymene, borneol, thymol and carvacrol amount in the total essential oil.
Results and Discussion
The oil compositions of the studied O. vulgare ssp. hirtum and O. onites populations are presented in Table I. Thirtyeight compounds were identified, accounting for more than 95% of the total oil. The oils of the two taxa were qualitatively similar; from the compounds identified, only calamenene was not detected in O. unites. On the contrary, a high quantitative oil variation was found, both within and between the two taxa. The major oil component of Greek oregano was either p-cymene (ranging from 17.7-51.3% of the total oil) or thymol (30.3-42.8%) orcarvacrol (57.4-69.6%), while Turkish oregano was always characterized by the preponderance of carvacrol (54.1-71.2%). Apart from the above constituents, high quantitative oil differences between the two taxa were found in the amounts of sabinene, myrcene, [gamma]-terpinene and borneol (difference of their mean values > 1) (Table I).
In order to find out if any ordination of the studied oils exists, a PCA was applied using as variables the amounts of sabinene, myrcene, [gamma]-terpinene, p-cymene, borneol, thymol and carvacrol. In Figure 2, the eigenvalues are presented along the first two components, accounted for the 89.5% of the total variance. The Greek oregano oils were distinguished by higher p-cymene and they were further divided into two subgroups, mainly due to the opposite trend in the participation of thymol and carvacrol. On the other hand, the Turkish oregano oils formed a distinct group, characterized by higher quantities of sabinene, myrcene, [gamma]-terpinene, borneol, and carvacrol.
A literature survey was carried out to confirm that the above compounds could be used for the distinction of the two oregano taxa. In total, the essential oils of 86 O. vulgare ssp. hirtum and 29 O. onites different populations, covering the whole distribution range of both species, have been up-todate studied. The comparison of their oils showed that:
(i) Except for a single report showing the occurrence of linalool-rich (> 90% of the total oil) O. onites plants in S Turkey (12), the oils of the two oregano taxa were characterized by the preponderance of the compounds involved in the phenolic biosynthetic pathway (6-7,9-10,12,17-33).
(ii) Thymol and carvacrol content varied greatly in Greek oregano oils, ranging from 0% to 90.2 % and from 1.7% to 93.8% of the total oil, respectively. Turkish oregano oils were constantly characterized by high carvacrol (> 30%) and low thymol (
(iii) Noticeable differences were found in borneol content of the two taxa (up to 1.6% in Greek and up to 8.2% in Turkish oregano). The ranges of sabinene and myrcene contents were almost similar (Figures 3C, 3D).
Concluding, the above evidence shows that the two oreganos, Greek and Turkish, had a similar oil composition. However, the concentration of certain compounds maybe helpful for their distinction. Thus, a thymol content > 6% and/or a pcymene content > 14% suggest that the oil was obtained from O. vulgare ssp. hirtum. In a thymol and/or p-cymene poor oil ( 2% indicates that the oil was obtained from O. onites.
1. S. Padulosi, Oregano. Promoting the conservation and use of underutilized and neglected crops. IPGRI, Rome (1997).
2. J. H. letswaart, A taxonomic revision of the genus Origanum (Labiatae). Ph.D. Thesis, Leiden University Press, The Hague (1980).
3. J.H. letswaart, OriganumL. In: The flora of Turkey and the East Aegean islands. Edit., P.M. Davis, pp 297-313, Edinburgh University Press, Edinburgh (1982).
4. D. Biondi, P. Cianci, C. Geraci and G. Ruberto, Antimicrobial activity and chemical composition of essential oils from Sicilian aromatic plants. Flav. Fragr. J., 8, 331-337 (1993).
5. D. Vokou, S. Vareltzidou and P. Katinakis, Effects of aromatic plants on potato storage. Agric. Ecosyst. Environ., 47, 223-235 (1993).
6. A. Sivropoulou, E. Papanikolaou, C. Nikolaou, S. Kokkini, T. Lanaras and M. Arsenakis, Antimicrobial and cytotoxic activities of Origanum essential oils. J. Agric. Food Chem., 44, 1202-1205 (1996).
7. V. Lagouri, G. Blekas, M. Tsimidou, S. Kokkini and D. Boskou, Composition and antioxidant activity of essential oils from Oregano plants grown wild in Greece. Z. Lebensm. Unters. Forsch., 197, 20-23 (1993).
8. M. Milos, J. Mastelic and I. Jerkovic, Chemical composition andantioxidant effect of glycosidically bound volatile compounds from Oregano (Origanum vulgare L. ssp. hirtum). Food Chem., 71, 79-83 (2000).
9. K. Adam, A. Sivropoulou, S. Kokkini, T. Lanaras and M. Arsenakis, Antifungal activities of Origanum vulgare ssp. hirtum, Mentha spicata, Lavandu/a angustifolia and Sa/via fruticosa essential oils against human pathogenic fungi. J. Agric. Food Chem., 46, 1739-1745 (1998).
10. I. Karpouchtsis, E. Pardali, E. Feggou, S. Kokkini, Z. Scouras, and P. Mavragani-Tsipidou, lnsecticidal and genotoxic activities of oregano essential oils. J. Agric. Food Chem., 46, 1111-1115 (1998).
11. Y. Oka, S. Nacar, E. Putievsky, U. Ravid, Z. Yaniv and Y. Spiegel, Nematicidal activity of essential oils and their components against the root-knot nematode. Nematology, 90, 710-715 (2000).
12. K.H.C. Baser, T. Ozek, G. Turnen and E. Sezik, Composition of the essential oils of Turkish Origanum species with commercial importance. J. Essent. oil Res., 5, 619-623 (1993).
13. F.W. McLafferty, Wiley Registry of Mass Spectral Data. 5th edition, John Wiley & Sons Inc., New York (1989).
14. A. Cornu and R. Massot, Compilation of Mass SpectraL Data. Heyden, London (1979).
15. W. Jennings, and T. Shibamoto, Qualitative Analysis of Flavour and Fragrance Volatiles by Glass Capillary Gas Chromatography. Academic Press, New York (1980).
16. H.G. Gauch, Ordiflex. A flexible computer program for four ordination techniques: weighted averages, polar orientation, principal component analysis and reciprocal averaging. Ecology and Systematics, Cornell University, Ithaca, New York (1977).
17. H. Y. Rhyu, Gas Chromatographie characterization of oregano and other spices of the Labiatae family. J. Food Sei. 44, 1373-1378 (1979).
18. A. Fleisherand N. Sneer, Oregano spices and Origanum chemotypes. J. Sei. Food Agrie., 33, 441-446 (1982).
19. U. Ravid and E. Putievsky, Carvacrol and thymol chemotypes of east Mediterranean Labiatae herbs. In: Progress in Essential oil Research. Edit. E.-J.Brunke,pp163-167,WalterdeGruyter&Co, Berlin, New York (1986).
20. JJ.C. Scheffer, A. Looman and A. Baerheim Svendsen, The essential oils of three Origanum species grown in Turkey. In: Progress in Essential oil Research. Edit. E.-J. Brunke, pp 151-156, Walterde Gruyter & Co, Berlin, New York (1986).
21. A. Akgul and A. Bayrak, Constituents of essential oils from Origanum species growing wild in Turkey. Planta Med., 53, 114 (1987).
22. A. Fleisher and Z. Fleisher, Identification of biblical hyssop and origin of the traditional use ofOregano-group herbs in the Mediterranean region. Econ. Bot., 42, 232-241 (1988).
23. D. Vokou, S. Kokkini and J.-M. Bessiere, Origanum onites (Lamiaceae) in Greece: Distribution, volatile oil yield and composition. Econ. Bot.,42, 407-412 (1988).
24. N. Arnold, B. Bellomaria, G. Valentini and HJ. Arnold, Comparative study of the essential oils from three species of Origanum growing wild in the eastern Mediterranean region. J. Essent. oil Res., 5,71-77 (1993).
25. S. Kokkini and D. Vokou, The hybrid Origanum intercedens from the island of Nisyros (SE Greece) and its parental taxa; comparative study of essential oils and distribution. Biochem. Syst. Ecol., 21,392-403 (1993).
26. G. Ruberto, D. Biondi, R. MeIi and M. Piattelli, Volatile flavour components of Sicilian Origanum onites L Flav. Fragr. J., 8, 197-200 (1993).
27. E. Sezik, C. Turnen, N. Kirimer, T. Ozekand K.H.C. Baser, Essentialoil composition of four Origanum vulgare subspecies of Anatolian origin. J. Essent. oil Res., 5, 425-431 (1993).
28. D. Vokou, S. Kokkini and J.-M. Bessiere, Geographic variation of Greek Oregano (Origanum vulgare ssp. hirtum) essential oils. Biochem. Syst. Ecol., 21, 287-295 (1993).
29. K.H.C. Baser, T. Ozek, M. Kurkcuoglu and G. Tumen, The essential oil content of Origanum vulgare ssp. hirtum of Turkish origin. J. Essent. oil Res., 6, 31-36(1994).
30. M. Skoula, P. Gotsiou, G. Naxakis and C.B. Johnson, A chemosystematic investigation on the mono- andsesquiterpenoids in the genus Origanum (Labiatae). Phytochemistry, 52, 649-657 (1999).
31. K. Karamanoli, D. Vokou, U. Menkissoglu and H.-I. Constantinidou, Bacteria/colonization of phyllosphere of Mediterranean aromatic plants. J. Chem. Ecol., 26, 2035-2047 (2000).
32. J. Mastelic, M. Milos and I. Jerkovic, Essential oil and glycosidically bound volatiles of Origanum vulgare L. ssp. hirtum (Link) letswaart. Flav. Fragr. J., 15, 190-194(2000).
33. N. Azcan, M. Kara, D.T. Asilbekova, T. Ozekand K.H.C. Baser, Lipidsand essential oil of Origanum onites. Chem. Nat. Compd., 36,132-136 (2000).
34. S. Kokkini, R. Karousou, A. Dardioti, N. Krigas and T. Lanaras, Autumn essential oils of Greek Oregano. Phytochemistry, 44, 883-886 (1997).
35. I. Jerkovic, J. Mastelic and M. Milos, The impact of both the season of collection and drying on the volatile constituents of Origanum vulgare L. ssp. hirtum grown wild in Croatia. Int. J. Food Sei. Technol., 36,649-654 (2001).
Stella Kokkini,* Regina Karousou and Effie Hanlidou
Laboratory of Systematic Botany and Phytogeography, Aristotle University, 540 06 Thessaloniki, Greece
Department of Botany, School of Biology, Aristotle University, 540 06 Thessaloniki, Greece
* Address for correspondence
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Received: December 2001
Revised: March 2002
Accepted: july 2002
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