1. 6th International Congress of Aromatic and Medicinal Plants (CIPAM), 29 May – 1 June 2016, Coimbra, Portugal
Essential Oil Content and Composition of Some Oregano Species (Origanum spp.) Cultured in Denizli District of Turkey, Turkish Oregano Production Center in the World 
Hasan BAYDAR
Suleyman Demirel University Faculty of Agriculture
Department of Field Crops
Isparta –Turkey
Olcay ARABACI
Adnan Menderes University Faculty of Agriculture Department of Field Crops Aydın –Turkey
Objective
The main purpose of this research is to determine the essential oil yield and composition of Origanum onites L. (Turkish oregano), O. vulgare subsp. hirtum (Link) Iestwaart (Greek or Istanbul oregano) and O. sipyleum L. (Anatolian oregano) cultured in Denizli district which is the main oregono production center in the world.
Introduction
Turkey supplies more than 50% of the world’s exported oregano (Origanum types). Denizli province is the primary oregano cultivation center in the country in both production and exporting (Figure 1). Although the main oregano species cultivated in the province is Turkish oregano (O. onites) (Picture 1), recently O. vulgare subsp. hirtum and O. sipyleum have also started to cultivate in limited field areas in Denizli district. Anatolian oregano is an endemic species of the Western Anatolia, Turkey.
After “Turkish Tobacco Law” was enacted in 2002, Turkish oregano was tried as an alternative product in Denizli province, southwestern part of Turkey. In this process, Turkish oregano production areas increased in parallel with decreases in the tobacco cultivation lands in the city. In the last 15 years, Denizli has become the only city that produces over 90% of Turkey’s oregano production. In 2015 in Denizli, 11,000 tones of dried oregano produced on approximately 9,500 ha field land (Picture 2). Besides, oregano processing and oregano oil production facilities were built in Gözler (a town that is the main production center of Denizli province) Agricultural Development Cooperative in 2004 with the contributions of Denizli Special Provincial Administration. Oregano leaf produced in the region is exported to many countries including EU and USA.
Agricultural Practices
In Denizli, oregano seeds are breaded into seedbed, prepared in 15 October-15 December similar to tobacco production. Approximately 1.5 g seeds are put into 1 m2 seedbed. Top of the seedbeds are covered with a plastic covers with 50 cm height. Approximately 100 m2 seedbeds are needed for 1 ha oregano plantation. From the seeds planted in autumn, enormous seedlings are produced in spring. At the end of March or the beginning of April, oregano is with dibble or manually planted with cm row spacing and cm row top spacing (150,000 seedling is needed for 1 ha land).
As oregano is planted on dry lands, watering is not made which is why the land is mowed once a year. Oregano harvesting starts on the last week of June, when plants are flowering, and lasts until the midst of July. Oregano harvesting is made manually with the help of reaping hook or with harvest machines (Picture 3). But as some other kinds of grasses are harvested during the machine process, products aren’t very qualified. Mowed oregano (water ratio is % in ground surface organs during mowing) are dried on the fields as bunches and moved into the places where they will be threshed. When they are dried for one week, their leaves and sticks are separated either with the cylinders or by putting them into threshing machines. Wire sieves with different aperture sizes are used for leaf/stick separation (Picture 4). Threshing machines cause low quality as sticks are mixed with oregano and leaves are crumpled too much. Separated oregano leaves are dried until their moisture decrease below 12%, and can be preserved in cool, dry and dark storages for one year without any significant change in quality. Dry oregano sticks can not be used in distillation as they contain very little essential oil.
Conclusion
According to the results of chemical soil analysis, oregano soils in the region were generally medium-textured and non-salinity, but high alkaline and excessively calcareous, and with low levels of organic matter. The leaf percentage of the dry herb was 16.2% in O. spyleum, 19.3% in O. onites and 39.3% in O. vulgare (Table 1). Essential oil content of oregano should be at least 2% according to ASTA standards. When this level is taken into consideration, essential oil contents of Turkish, Greek/Istanbul and Anatolian oreganos grown in non-irrigated, loamy and alkali soils of Denizli district were higher than the limit specified. The highest oil yield in dry leaf was 2.3% in O. vulgare subsp. hirtum, and the highest oil yields in dry flower was 4.5% in O. onites (Table 2). The main compound in the essential oil of the all oregano species examined in this study was carvacrol. Carvacrol percentages in the leaf and flower essential oils were and 87.83% in O. onites, and 81.96% in O. vulgare subsp. hirtum, and 85.71% in O. sipyleum, respectively. Essential oils distilled from the dried flowering tops contained more carvacrol than that of the essential oils distilled from the dried leaves (Table 3).
Picture 1. Turkish oregano (Origanum onites L.)
Materials and Methods
In this research, essential oil content and composition of Origanum onites L. (Turkish oregano), Origanum vulgare subsp. hirtum (Link) Iestwaart (Greek or Istanbul oregano) and O. sipyleum L. (Anatolian oregano) cultured in Denizli district at about 1200 m altitude during flowering period on July, 2011 were mowed from 15 cm upper during oregano flowering season. After they were dried in room conditions, leaves, flowers and sticks were separated and their dry herb representation ratios (%) were calculated. Additionally, their % essential oil contents (v/w) were determined by distilling them in Clevenger type water distillation apparatus for 3 hours. Essential oil ingredients of leaf/flower oils were detected by GC/MS (Detector: QP-5050, Column: CP-Wax 52 CB (50 m x 0.32 mm, 0.25 µm).
Climatic data
According to the registrations of Denizli Provincial Directorate of Meteorology, annual average temperature is 13.1 oC, annual average high temperature is 19.4 oC, annual average low temperature is 6.6 oC, average lowest temperature in January is -1.8 oC, average highest temperature in July is 31.0 oC, autumn early frost date is 27 September -0.6 oC, spring late frost date is 11 April -3.0 oC, number of cloudy days is 186, number of overcast days is 47, annual average rainfall is mm and most rainy month is December.
Picture 2. Oregano fields in Denizli province of Turkey
Table 1. Parts in dry herb of oregano species
Species
Parts in Dry Herb
Leaf (%)
Flower (%)
Stem (%)
Origanum onites
19.3
52.2
28.5
Origanum vulgare
39.3
12.1
48.6
Origanum sipyleum
16.2
21.7
62.1
Table 2. Essential oil yields of oregano species
Species
Essential Oil Yield
Leaf (%)
Flower (%)
Origanum onites
2.1
4.5
Origanum vulgare
2.3
4.4
Origanum sipyleum
0.4
2.5
Picture 4. Threshing and sieving oregano by a peasant in Gözler town, the main production center in Denizli province
Figure 1. Denizli province located in the southwestern part of Turkey
Table 3. Essential oil compounds from oregano species cultured in Denizli province of Turkey
Compounds
Retention
time
Origanum onites
Origanum vulgare hirtum
Origanum sipyleum
Leaf
Flower
α-pinene
6.4
1.80
1.21
2.09
2.20
2.52
1.43
β-myrcene
11.0
0.73
1.20
3.10
2.65
1.52
1.93
α-terpinene
12.0
0.49
1.10
0.76
2.35
0.00
γ-terpinene
15.1
2.42
5.48
7.81
7.71
19.12
4.64
p-cymene
16.5
3.79
4.73
2.43
1.53
4.41
β-terpineol
27.9
0.38
0.44
0.57
Linalool
32.3
0.63
t-caryophyllene
35.9
0.51
0.29
0.37
0.92
3.23
Thymol methyl ether
36.2
2.31
1.37
6.45
1.85
Borneol
42.0
0.30
0.82
Thymol
67.4
2.82
0.20
Carvacrol
68.7
84.03
87.83
78.23
81.96
60.74
85.71
Picture 3. Oregano harvest in Denizli province of Turkey