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Introduction
The Iranian endemic plant Mentha mozaffarianii Jamzad belongs to the Lamiaceae family and is known locally as "Pooneh-Koohi" [1]. Six species and several subspecies of the genus Mentha are found in Iran, among which just M. mozaffarianii is endemic. It has a limited geographical range in the south of Iran and is just found in Siyahoo, Qotb-Abad, Damtang and Sikhoran in Hormozgan Province [2]. The leaves and seeds have been commonly used in Iranian traditional medicine as antiseptic, analgesic, and to treat painful menstruation, dyspepsia, arthralgia, fever, headache, common cold, and healing wound [1-3]. Literature survey revealed reports just on the essential oil composition of the leaves and the aerial parts of M. mozaffarianii and there was no attempt to study the essential components of M. mozaffarianii seeds up to now. Regarding the significant pleasant odor of the seeds, we were prompted to investigate the essential oil composition of this part of M. mozaffarianii for the first time.
Results and Discussion
The hydrodistillation of M. mozaffarianii seeds gave pale yellow oil with pleasant odor and yield of 2.4% (v/w) based on the fresh weight. Fig. 1 shows the gas chromatogram of M. mozaffarianii seed essential oil.
Table 1 shows the list of compounds whose GC-MS concentration is not less than 0.1% of total peak concentration. According to Table 1, 25 components were identified in the seeds essential oil which presented about 96.8% of the total composition. The major constituents of M. mozaffarianii seed oil were characterized as piperitenone (35.6%), piperitone (27.1%) and 1,8-cineol (10.7%). The studied essential oil comprised one hydrocarbon (0.2%), 17 monoterpenoids (94.4%), six sesquiterpenoids (3.2%) and one phenylpropanoid (0.3%).
Table 1 GC-MS analysis of M. mozaffarianii seed essential oil.
ª Compounds listed in order of elution.
b KI (Kovats index) measured relative to n -alkanes (C9-C28) on the non-polar DB-5 column under condition listed in the Materials and Methods section.
c KI, (Kovats index) from literature.
Piperitenone as the major component of the studied oil is a monoterpene ketone. According to Fujita et al. [4] piperitenone appears first in young leaves of Mentha species and then converts to pulegone or piperitone via two separate pathways in older leaves. The current results showed that most of the first appeared piperitenone was converted to piperitone. High and low amounts of piperitone (27.1%) and pulegone (4.6%) respectively in the seeds oil demonstrate a characteristic metabolic pathway in M. moaffarianii in which piperitenone could highly be metabolized to piperitone rather than pulegone. As literature survey there were just two reports on the essential oil composition of the leaves and aerial parts of M. mozaffarianii [3, 5]. A comparison of the results with the literature showed that the seeds oil composition was so similar to the leaves oil composition reported by Arman et al. [3]. That is because both samples were collected from the same region in Hormozgan Province. Regarding the results reported by Arman et al [3], presence of piperitenone as the main component in the seeds and the leaves oils of M. mozaffarianii is characteristic. However, the piperitenone content in M. mozaffarianii leaves oil was reported as two times more than that in the seeds oil. Higher amounts of piperitenone (59.5%) in the essential oil of M. mozaffarianii leaves could be related to the stage of plant growth. According to Arman et al . M. mozaffarianii was collected at full flowering stage. Since the leaves were young at this stage, piperitenone content was expected in maximum and Arman et al . report also confirmed it. Mature seeds appear at the time the plant gets older. As the current results about half of the piperitenone content has converted to piperitone. Absence of piperitenone epoxide in the seeds oil is considerable. It was reported by Arman et al . [3] as the second major component in the leaves oil of M. mozaffarianii . Rustayian et al . [5] reported 1,8-cineol with a high amount of 53.5% in the essential oil of aerial parts of M. mozaffariani while it contained 10.7% of the seed oil. Differences between M. mozaffarianii seeds oil chemical profile and that of the leaves reported by Rustayian et al . could be mainly related to the factors such as geographic origin and the season where the collection took place.
As piperitenone is found to be one of the main metabolites of the potent hepatotoxin, pulegone in the body [6], M. mozaffarianii could be regarded as a toxic plant and due to its traditional use as a folklore medicine future toxicology investigations are suggested.
This paper presents the essential oil composition of seeds of the endemic species M. mozaffarianii for the first time. Regarding the essential oil major components, further biological studies are suggested to investigate the pharmacological and therapeutic properties of the seeds.
Experimental
Plant material
Fresh seeds of M. mozaffarianii were collected in June 2015 from Bekhan village, Fareghan, Hadji-Abad County (Tangezaq Mountains), Hormozgan Province, Iran: (28°18′33″N, 55°54′06″E, 1700 m). Specimens were identified by R. Asadpour and voucher was deposited in the Herbarium of Pharmaceutical Sciences Branch, Islamic Azad University (IAUPS), Tehran under code number 419-PMP/A. Seeds were powdered and submitted to hydrodistillation in a Clevenger-type apparatus for 3 hours. At the end of distillation the oil was collected, dried with anhydrous Na2SO4, measured, and transferred to a clean glass vial and kept at a temperature of −18 °C for further analyses.
Analysis of the essential oil
Oil sample analyses were performed on a HP-6890 gas chromatograph (GC) equipped with a FID and a DB-5 capillary column, 30 m × 0.25 mm, 0.25 μm film thickness, temperature programmed as follows: 60-240 °C at 4 °C/min. The carrier gas was N2 at a flow of 2.0 ml/min; injector port and detector temperature were 250 °C and 300 °C, respectively. Sample was injected by splitting and the split ratio was 1:10. GC-MS analysis was performed on a Hewlett-Packard 6890 /5972 system with a DB-5 capillary column (30 m × 0.25 mm; 0.25 μm film thickness. The operating conditions were the same conditions as described above but the carrier gas was He. Mass spectra were taken at 70 eV. Scan mass range was from 40-400 m/z at a sampling rate of 1.0 scan/s. Quantitative data were obtained from the electronic integration of the FID peak areas. The components of the oil were identified by their retention time, retention indices, relative to C5-C28 n-alkanes, computer matching with the Wiley 275.L library and as well as by comparison of their mass spectra with data already available in the literature [7, 8]. The percentage of composition of the identified compounds was computed from the GC peaks areas without any correction factors and was calculated relatively. The analyses of the essential oil are the average of three replicates.
