Chemical Composition and Monoterpenoid Enantiomeric Distribution of the Essential Oils from Apharsemon (Commiphora gileadensis)

Background: Commiphora gileadensis (Hebrew: apharsemon) has been used since Biblical times to treat various ailments, and is used today in the traditional medicine of some Middle Eastern cultures. Methods: The essential oils from the stem bark, leaves, and fruits of Commiphora gileadensis—collected at the Ein Gedi Botanical Garden, Israel—were obtained by hydrodistillation and analyzed by gas chromatography–mass spectrometry. In addition, the enantiomeric distributions of the monoterpenoids in the essential oils have been determined by chiral gas chromatography. Results: The essential oils were dominated by monoterpene hydrocarbons, followed by oxygenated monoterpenoids. The major components in C. gileadensis oils were the monoterpenes α-pinene (11.1–18.4%), sabinene (15.8–35.9%), β-pinene (5.8–18.0%), p-cymene (4.8–8.4%), limonene (1.3–6.2%), γ-terpinene (0.7–8.1%), and terpinen-4-ol (5.3–18.5%). The (–)-enantiomers predominated for α-pinene, sabinene, β-pinene, limonene, and terpinen-4-ol. Conclusions: The chemical compositions of the C. gileadensis essential oils from Israel are markedly different from previously reported samples, which were rich in sesquiterpenoids. Likewise, the enantiomeric distribution of monoterpenoids is very different from Boswellia spp. essential oils.

shore of the Dead Sea, unraveled furnace-like structures, jars, and other objects dating from the sixth century B.C.E. that were comparable with those found in perfume-making workshops. This supports the historical references. In the 1990s, C. gileadensis was reintroduced to Israel and is currently cultivated in Ein Gedi, near the Dead Sea [8], renewing a long lost part of Jewish history in the land of Israel.
C. gileadensis has been used historically to treat a wide array of ailments [9][10][11][12][13], and is used today in the traditional medicine practices of some cultures in the Middle East. In Yemen and Oman, the bark exudate is used externally to treat skin disorders such as burns, wounds, and infections [6,14,15]. Among the Arab populations in the Middle East, a decoction of the aerial parts of the plant is administered as a pain reliever, a diuretic, and a laxative [16,17]. In 2010, Iluz et al. [6] investigated the medicinal properties of C. gileadensis and demonstrated that its sap had an inhibitory effect against Bacillus cereus and was capable of blocking lectins of Pseudomonas aeruginosa. This confirms the historical sources that indicated the antiseptic properties of the balsam's sap. In 2012, Amiel et al. [18] further supported this finding by showing that (E)-caryophyllene was a key component in C. gileadensis essential oil, that the balsam's stem extracts acted against cancerous tumor cells, and had apoptosis-inducing properties that acted selectively, eradicating tumor cells, but not healthy cells.
Although C. gileadensis has been an important medicinal plant throughout history, information about the essential oil composition of wild C. gileadensis is lacking. Therefore, in this work, the essential oil compositions attained from the stem bark, leaves, and fruits of wild C. gileadensis collected in Ein Gedi, Israel were determined and compared to the composition of commercially used C. gileadensis oil. In addition, to further characterize the essential oils, the enantiomeric distributions of the monoterpenoids in C. gileadensis essential oils were determined.

Plant Material
Leaves, stems, and fruits of C. gileadensis were collected at the Ein Gedi Botanical Garden. The plant was identified and collected by Nativ Dudai. Plant parts were placed within a Clevenger-type apparatus for 1.5 h and the essential oil was hydro-distilled. The commercial samples were produced by a steam distillation apparatus and supplied by the grower Mr. Guy Erlich from his plantation at Almog (near the Dead Sea), Israel.

Gas Chromatography-Mass Spectrometry
The essential oil compositions of wild and commercial C. gileadensis were analyzed by GC-MS using a Shimadzu GCMS-QP2010 Ultra (Shimadzu Scientific Instruments, Columbia, MD, USA) operated in the electron impact (EI) mode (electron energy = 70 eV) with a scan range of 40-400 amu and a scan rate of 3.0 scans/s, and GC-MS solution software. The GC column was a ZB-5 fused silica capillary column (Phenomenex, Torrance, CA, USA), 30 m length × 0.25 mm inner diameter, with a (5% phenyl)-polymethylsiloxane stationary phase and a film thickness of 0.25 µm. The carrier gas was helium, with a column head pressure of 552 kPa and flow rate of 1.37 mL/min. Injector temperature was 250 • C and the ion source temperature was 200 • C. The GC oven temperature program was set for an initial temperature of 50 • C and increased at a rate of 2 • C/min to 260 • C. A 5% w/v solution of the sample in CH 2 Cl 2 was prepared, and 0.1 µL was injected with a splitting mode of 30:1. Identification of the oil components was based on retention indices determined by reference to a homologous series of n-alkanes, and by comparison of their mass spectral fragmentation patterns with those reported in the literature [19] and stored in our in-house MS library. Percentages were determined based on total ion current integrations of the peak areas, and are uncorrected.

Chiral Gas Chromatography-Mass Spectrometry
Chiral analysis of the essential oils of wild and commercial C. gileadensis was performed on a Shimadzu GCMS-QP2010S (Shimadzu Scientific Instruments, Columbia, MD, USA) operated in the EI mode (electron energy = 70 eV) with a scan range of 40-400 amu and a scan rate of 3.0 scans/s The GC was equipped with a Restek B-Dex 325 capillary column (Restek Corp., Bellefonte, PA, USA) (30 m × 0.25 mm ID × 0.25 µm film). The oven temperature began at 50 • C, and was then gradually raised to 120 • C at a rate of 1.5 • C/min. After reaching 120 • C, the oven temperature was increased to 200 • C at 2 • C/min intervals and kept at this temperature for 5 min. Helium was the carrier gas, and the flow rate was maintained at 1.8 mL/min. Samples were diluted to 3% w/v with CH 2 Cl 2 , and a 0.1 µL sample was injected in a split mode at a split ratio of 1:45. The monoterpenoid enantiomers were identified by comparison of retention times with authentic samples obtained from Sigma-Aldrich (Milwaukee, WI, USA). Relative enantiomer percentages were determined based on peak areas.

Conclusions
The chemical composition of essential oils from the stems, leaves, and fruits of Commiphora gileadensis have been shown to be rich in monoterpenoids, but a dearth of sesquiterpenoids, in contrast to previous reports of C. gileadensis essential oils; there is apparently wide variation in C. gileadensis volatiles. The enantiomeric distribution of monoterpenoids showed little variation Chiral gas chromatography has been used as an analytical technique to detect outliers from authenticated oils and the possible adulteration of commercially important essential oils [37]. Since C. gileadensis has the potential for commercial utilization, this study serves to establish the enantiomeric distributions of the monoterpenoids in authentic unadulterated C. gileadensis essential oils. In addition, this work provides a comparison between C. gileadensis and other members of the Burseraceae (Boswellia spp.).

Conclusions
The chemical composition of essential oils from the stems, leaves, and fruits of Commiphora gileadensis have been shown to be rich in monoterpenoids, but a dearth of sesquiterpenoids, in contrast to previous reports of C. gileadensis essential oils; there is apparently wide variation in C. gileadensis volatiles. The enantiomeric distribution of monoterpenoids showed little variation between the different essential oil samples of C. gileadensis, contrasted markedly from Boswellia spp. essential oils.