Essential Oil Composition of Five Sideritis Species Endemic to Turkey

1Balikesir University, Science & Arts Faculty, Chemistry Department, 10145, Balıkesir 2Balikesir University, Altinoluk Vocational School, Medicinal and Aromatical Plants Programme, 10870, Balıkesir 3Bezmialem Vakif University, Faculty of Pharmacy, Department of Basic Pharmaceutical Sciences 34093, Istanbul, Turkey 4Balıkesir University, Necatibey Education Faculty, Department of Science & Mathematic Educations, 10100, Balıkesir, Turkey

Although there are some studies on the essential oil composition of the five species [6], locality, climatic and seasonal conditions are affect the chemical constituents of the plants.For these reasons, in this study, we decided to re-examine the essential oil contents of Sideritis phrygia Bornm.(SP), Sideritis pisidica Boiss.& Heldr.(SPi), Sideritis brevibracteata P. H. Davis (SB), Sideritis bilgerana P. H. Davis (SBi) and Sideritis hispida P. H. Davis (SH) which were collected in July 2014.

Plant material
The aerial parts of five Sideritis species were collected during the full-flowering season in July 2014 from different location in Turkey (Table 1).The species were identified by Prof. Dr. Tuncay Dirmenci from Balıkesir University.The voucher specimens were deposited at the Herbarium of Faculty of Education, Balıkesir University, Balıkesir, Turkey.

Isolation of essential oil
The air-dried aerial parts of the plants were chopped into small pieces and subjected to hydrodistillation with water for 4 h, using a Clevenger-type apparatus to produce the essential oil.The obtained essential oils were stored in amber vials at 4 o C further analyses.The oil yields of species were given in the Table 1.

GC-MS conditions
GC-MS was conducted on Thermo Electron Trace 2000 GC model gas chromatography and Thermo Scientific TSQ GC-MS/MS.A Phenomenex DB5 fused silica column (30 m x 0.32 mm, with 0.25 µm film thickness) was used with helium as a carrier gas at 1mL/minute flow rate (138 kPa).Detailed procedures of GC-MS conditions and indentification of compounds were reported previously in the literature [13].

Results
The chemical content of essential oils of the studied species were given in Table 2.The essential oil contents of five Sideritis species were classified into seven groups as hydrocarbons and derivatives, monoterpene hydrocarbons, oxygenated monoterpenes, sesquiterpene hydrocarbons, oxygenated sesquiterpenes, diterpene alcohols and phenolic compounds (Table 2).
In the essential oil of SP, thirty four compounds were identified representing the 93.5% of the total oil.Monoterpene hydrocarbons were the dominant group (39.5%) in the essential oil of SP.Limonene (10.6%) and p-cymene (10.1%) were main monoterpen compounds.Oxygenated sesquiterpenes were represented with 20.5% and caryophyllene oxide (11.4%) was determined as dominant compound.While diterpenes were not detected, sesquiterpene hydrocarbons were detected in scarce amounts (6.2%).
α-cadinol, α-cadinene, βcaryophyllene In previous studies, main compounds of essential oil of Sideritis species belonging to section of Empedoclia were classified by Kırımer et al. [6] in to three groups as monoterpenes rich, sesquiterpenes rich and diterpenes rich [6].According to the main constituents classified most of them were belong to monoterpene rich group and especially presence of α-and/or β-pinene was observed in particular.
Results of the comparison our study and previous study were given in Table 3.According to the previous studies, while SPi and SBi were determined as monoterpene rich (α-pinene and βpinene were major compound), in our study they were found sesquiterpene rich (β-caryophyllene).
Similarly previous studies, we found SP, SB and SH oil as sesquiterpene rich.

Discussion and Conclusion
The The major compound in the essential oil of SPi and SB was found to be β-caryophyllene (32.8% and 43.1%, respectively) while in the essential oil of SBi and SH was α-cadinol (28.1% and 41.1%, respectively).Additionally caryophyllene oxide (11.4%) was determined as main compound of the essential oil of SP.These results indicate that chemical constituents in the essential oils and the amounts of the major compounds showed difference, according to the geographical location, season, climatological variations, plant variety and experimental conditions investigated parts of the plants [17][18][19][20].

Table 1 .
List of the Sideritis species with locality, collection time and oil yields (%)

Table 2 .
Essential oil composition (%) of the studied Sideritis species

Table 3 .
The main compounds of the studied species