SQU Journal for Science, 2016, 21(1), 7-15 © 2016 Sultan Qaboos University 7 Comparison of Chemical Composition and Antioxidant Activity of Four Essential Oils Extracted from Different Parts of Juniperus excelsa Saleh N. Al-Busafi*, Salim H. Al-Saidi, Amani I. Al-Riyami and Nawal S. Al-Manthary Department of Chemistry, College of Science, Sultan Qaboos University, P.O. Box: 36, PC 123, Al-Khod, Muscat, Sultanate of Oman.*Email: saleh1@squ.edu.om. ABSTRACT: The chemical contents and compositions of four essential oils extracted from leaves, branches, fruits and gum-resin of Juniperus excelsa from Jabal Al-Akhdhar in the Sultanate of Oman were studied using infra-red (IR) spectroscopy and gas chromatography-mass spectrometry (GC-MS). IR analysis revealed the presence of C-H, O-H, C=C and C=O functionality bonds with varied intensities. The GC-MS study showed the occurrence of 35 different monoterpenes of which 11 (31.43%) monoterpenes were shared by the four oils. α-Pinene was detected in branches and gum-resin oils as a major compound with different proportions (80.50% in gum oil and 79.03% in branches oil). The major component in leaf and fruit oils was the monoterpene limonene with proportions of 50.46% and 42.51%, respectively. Sesquiterpenes exist in leaf, branch and fruit essential oils but not in gum-resin oil. The essential oil of the leaves showed stronger antioxidant and radical scavenging activities than the other oils. Keywords: Juniperus excelsa; Essential oil; GC-MS analysis; Monoterpenes; Antioxidant; DPPH radical scavenging. مقاروت المحتوى الكَمَائٌ ودراست القذرة علي تثبَط التأكسذ ألربعت سٍوث عطزٍت مستخلصت مه أجشاء مختلفت مه شجزة العلعالن ، سالم السعَذً، أماوٌ الزٍامٌ، ووال المىذرًصالح البوصافٌ (Juniperus excelsa)حن دراست الوحخْٓ الكيويائي ألربؼت سيْث ػطزيت هسخخلصت هي أّراق ّأغصاى ّثوار ّلباى شجزة الؼلؼالى :الملخص الغاس الوزحبظ بجِاس كشف الكخلت. لقذ كشف لٌا الوٌخشزة في الجبل األخضز في سلطٌت ػواى باسخخذام طيف األشؼت ححج الحوزاء ّ كزّهاحْجزافيا بٌسب هخفاّحَ. بيٌوا C-H, O-H, C=C, C=Oجِاس طيف األشؼت ححج الحوزاء ػي ّجْد الزّابظ الكيويائيت الخاليت في هزكباث الشيْث الؼطزيت: هزّكب 11ث في الشيْث الؼطزيت األربؼت هٌِا هزكب كيويائي هخخلف هي ًْع الوًْْحيزبيٌا 53كشف جِاس الكزّهاحْجزافيا الغاسيت ػي ّجْد %79.03في سيج لباى الؼلؼالى ّ 5008.بيٌيي يْجذ في سيج األغصاى ّاللباى كجشء اساسي بكوياث هخخلفت: % -( هشخزك. هزّكب الفا31.43%) . يوخاس سيج لباى %42.5يج الثوار بٌسبت ّفي س% 50.46 في سيج أغصاى الٌباث بيٌوا يْجذ هزّكب الليوًْيي بكثزة في سيج األّراق بٌسبت لؼلؼالى الؼلؼالى بؼذم ّجْد هزّكباث السيسكْيخزبيي بيٌوا حْجذ ُذٍ الوزكباث بٌسب هخفاّحت في الشيْث الثالثت األخزٓ. يظِز سيج أّراق شجزة ا ًشاط أكبز ػلٔ كبح الخأكسذ هقارًت هغ الشيْث األخزٓ. .الؼلؼالى، سيْث طيارة، الكزّهاحْجزافيا الغاسيت، الوًْْحيزبيٌاث، حثبيج الخأكسذشجزة :الكلماث المفتاحَت 1. Introduction he Juniper tree (Juniperus excelsa) grows at an altitude of about 2,300 m on Jabal Al-Akhdar (Sultanate of Oman) in an open dry mountain forest under suitable conditions [1]. In addition, J. excelsa can be found throughout the eastern Mediterranean from northeastern Greece and southern Bulgaria across Turkey to Syria [2], and in the mountains of Iran, Pakistan, Saudi Arabia, and Yemen [3]. Traditionally, J. excelsa is used in folk medicine to treat different ailments such as abdominal rigidity, asthma, fever, headache, diabetes and leucorrhoea [4,6]. In other parts of the world, the plant is considered useful as an antihypertensive, diuretic, appetizer, carminative, stimulant, anticonvulsant, flavoring agent, and as a remedy for tuberculosis [7,8]. Bioactivity studies performed on J. excelsa have revealed antibacterial [9], antifungal [10], and bronchodilatory activities [11]. Sandracopimaric acid, a diterpene isolated from J. excelsa was found to exhibit significant antibacterial activity against Bacillus subtilis, Staphylococcus aureus and Streptococcus durans [12]. T mailto:saleh1@squ.edu.om mailto:saleh1@squ.edu.om SALEH N. AL-BUSAFI ET AL. 8 Moreover, hexane extract of the berries of J. excelsa exhibited potent activity against a human colon cancer cell line [13]. Chemical compositions of essential oil of J. excelsa leaves and fruits have revealed diverse ratios of monoterpenes and sesquiterpenes from one region to another. In this regard, chemical analysis of the essential oil of the leaves of J. excelsa from the Crimea revealed the presence of -pinene (56.2%), limonene (10.4%), -3-carene (3.1%), camphene (2.9%), -pinene (1.2%), -terpinene (1.9%) and terpinolene (0.8%) [14]. The essential oil (EO) extracted from the leaves of J. excelsa from Jammu (India) was reported to contain sabinene (36.1%) and cedrol (26.8%) as the major components [15]. Chemical analysis of the leaf oil of J. excelsa from Greece revealed the presence of cedrol (28.1%), -pinene (22.5%) and limonene (22.7%) as the major components [16]. The essential oil extracted from the J. excelsa fruits of Iran origin showed -pinene (89.5%), myrcene (2.6%), germacrene (2.2%), and limonene (1.3%) with other minor components [17]. Essential oil of the leaves of J. excelsa from Oman has been found to possess limonene (49.6%), germacrene (9.6%), -3-carene (5.9%), α- pinene (4.81%) and γ-cadinene (3.76%) [18]. In addition, the juniper tree produces gum-resin that appears on the surface of the branches. The chemical compositions of the essential oil extracted from the gum-resin of J. excelsa have not yet been described in the literature. In this study we analyzed the chemical contents and compositions of the essential oil of the gum-resin of J. excelsa along with essential oils of the leaves, branches and fruits using IR spectroscopy and GC-MS spectrometry. Additionally, the four extracted materials were subjected to antioxidant and radical scavenging activity tests. 2. Materials and Methods 2.1 Plant materials Gum resin, leaves, branches and fruits of J. excelsa were collected in October 2013 at Jabal Al-Akhdhar, Sultanate of Oman. The plant was botanically identified by Dr. Amina Al-Farsi at the Botanical section of the Life Science Unit, College of Science, Sultan Qaboos University. 2.2 Extraction of volatile oil Fresh 70.2 g, 152.0 g, 212.0 g and 230.4 g samples of gum-resin, leaves, branches and fruits, respectively, of J. excelsa were subjected to hydro distillation using Clevenger’s apparatus until complete exhaustion to yield 3.1 g (4.4%), 0.41 g (0.27%), 0.68 g (0.32%) and 1.2 g (0.52%) of essential oils respectively. The obtained oils were collected, dried over magnesium sulphate and kept at 4 0 C until analysis. The isolation percentage was calculated based upon the weight of the fresh materials used. IR spectra were obtained using the neat liquid method with a Nicolet model Magna 560 spectrometer; absorption bands are recorded in wave number (cm -1 ). 2.3 Gas chromatography-mass spectrometry The GC-MS analyses were carried out with a Shimadzu GC-MS-QP/5050A apparatus equipped with a quadrupole mass spectrometer and a J&W Scientific DB-5MS (5% phenyl / 95% dimethylpolysiloxane) fused-silica capillary column (30 m x 0.25 mm I.D. x 0.25 mm film thickness). The oven temperature was programmed to increase from 31˚C to 271˚C at 3 ˚C /min. Injector and interface temperatures were kept at 275 ˚C and 300 ˚C respectively. Helium was used as carrier gas with a linear velocity of 44.6 cm/s, column flow rate of 1.5 mL/min and total flow rate of 36 ml/min. The split ratio was 1:21. Mass spectra were continuously recorded over the mass range 35 to 501 amu. The MS operating parameters were as follows: ionization voltage 70 eV and scan rate 500 amu/s. The oil constituents were identified by comparison of their Kovat’s relative retention indices (RIs), determined relative to the retention times (tR) of a homologous series of n-alkanes (C8 – C30), with those reported in the literature. Additionally, the mass spectra obtained were compared to those recorded in the computer MS library (Wiley 229,000 database). The percentage composition was determined by using the single area percentage method without considering corrections for response factors. 2.4 Evaluation of total antioxidant activity by the phosphomolybdenum method The antioxidant activity of the essential oils was evaluated by the phosphomolybdenum method according to the procedure of Prieto et al. [19]. An aliquot of 0.3 ml of sample solution (1 mM in methanol) was combined in a 4 ml vial with 3 ml of reagent solution (0.6 M sulfuric acid, 28 mM sodium phosphate and 4 mM ammonium molybdate). The vials were capped and incubated in a water bath at 95 °C for 90 min. After the samples had cooled to room temperature, the absorbance of the mixture was measured at 695 nm against a blank. Triplicate measurements were made and the antioxidant activity was expressed as ascorbic acid (AA) equivalent using the following linear equation established using ascorbic acid as standard: [A = 0.0013 C + 0.049; R 2 = 0.974] where A is the absorbance at 695 nm and C the concentration of ascorbic acid (mg/L). The values are presented as the means of triplicate analysis. COMPARISON OF CHEMICAL COMPOSITION AND ANTIOXIDANT ACTIVITY 9 2.5 Free radical scavenging activity (DPPH, 2,2-diphenyl-1-picrylhydrazyl) The free radical scavenging activity of the essential oils was determined by the DPPH free radical method [20]. A 2.0 ml methanolic solution of DPPH (0.1 mM) was mixed with 0.1 ml of oil solution (0.1 mg/ml) in methanol and, after standing for 60 min, the absorbance of the mixture was measured at 517 nm against methanol as the blank. Triplicate measurements were made and the radical scavenging activity was calculated by the percentage of DPPH that was scavenged using the following formula: % Reduction = [(AB – AA)/AB] x 100, where AB is the absorption of blank sample and AA is the absorption of tested oil solution. 3. Results and Discussion The essential oils of different parts of J. excelsa were obtained by conventional hydrodistillation of the crushed fresh materials. The essential oil of the gum-resin of J. excelsa (4.4%) was a colorless oil which solidified with time to a white solid. This behavior can be attributed to the high percentage of oxygenated monoterpenes compared with other essential oils (Table 2). The essential oil of the leaves of J. excelsa (0.27%) was colorless oil which stayed liquid on standing. The essential oils of the branches of J. excelsa (0.32%) and of the fruits (0.52%) were light yellow. 3.1 IR analysis IR analysis of the essential oils of different parts of J. excelsa revealed the presence of four characteristic symmetrical stretching bands for O-H, C-H, C=O and C=C bonds (Table 1). The stretching frequency of the C-H bond ranged from 2916 cm -1 in fruits and leaves to 2965 cm -1 in gum-resin. The O-H stretching band varied from strong frequencies as in the essential oils of branches and fruits, at 3430 cm -1 and 3524 cm -1 respectively, to moderate and weak frequencies as in the essential oils of gum-resin and leaves. The C=O stretching frequency ranged from 1700 cm -1 in fruit oil to 1753 cm -1 in branch oil. Such frequency ranges indicate the presence of saturated carbonyl compounds. Table 1: IR data of essential oils of different parts of J. excelsa [s: strong; m: medium; w: weak] Functional group Wavenumber (cm -1 ) Gum-resin Leaves Branches Fruits O-H 3439 (m) 3418 (w) 3430 (s) 3524 (s) C-H 2965 (s) 2916 (s) 2941 (s) 2916 (s) C=O 1731 (m) 1740 (w) 1753 (w) 1700 (w) C=C 1685 (w) 1645 (s) 1654 (s) 1644 (s) 3.2 GC-MS analysis Twenty-five components, comprising 97%, were detected in the essential oil of J. excelsa gum-resin using GC- MS (Table 2, Figures 1 & 2). The major compound in the J. excelsa gum oil was α-pinene (80.50%); other compounds that were identified in minute proportions were E-pinocarveol (2.85%), limonene (2.46%) and E-verbenol (2.09%). Among the identified components, twelve compounds, comprising 48%, were monoterpene hydrocarbons and thirteen compounds, comprising 52%, were oxygenated monoterpenes. The oil was characterized by the absence of sesquiterpenes. The essential oil of the branches of J. excelsa contained 39 compounds. The major component in the branch oil was α-pinene (79.03%), followed by limonene (2.20%), myrcene (1.53%), and β-pinene (1.20%). Amid the revealed compounds, twelve, comprising 31%, were monoterpene hydrocarbons and ten, comprising 26%, were oxygenated monoterpenes. The essential oil of the branches of J. excelsa was distinguished by the presence of seventeen sesquiterpenes (44%). Thirty-seven compounds, comprising 98%, were identified in the EO of the leaves of J. excelsa. Limonene (50.46%) and α-pinene (31.67%) were the major compounds. Other compounds found to exist in minor proportions were myrcene (2.53%) and 3-carene (1.87%). Twelve compounds, comprising 32%, were monoterpene hydrocarbons and ten compounds, comprising 27%, were oxygenated monoterpenes. Fifteen sesquiterpenes, comprising 41%, of the oil were identified. The EO of the fruits of J. excelsa contained thirty-four components, comprising 98% of the oil. The major compounds were limonene (42.51%) and α-pinene (35.09%) followed by myrcene (3.09%), β-eudesmol (2.16%), -3-carene (2.14%) and α-humulene (2.11%). Twelve compounds, comprising 35%, were identified as monoterpene hydrocarbons and five compounds comprising 15% were oxygenated monoterpenes. The oil was characterized by the presence of seventeen sesquiterpenes comprising 50% of the oil. SALEH N. AL-BUSAFI ET AL. 10 Table 2. Chemical composition of essential oils of different parts of Juniperus excelsa Compounds RI Percentage in Gum-resin Branches Leaves Fruits Tricyclene 928 0.77 0.36 0.29 0.09 α-Thujiene 932 0.19 0.22 _ _ α-Pinene 942 80.50 79.03 31.67 35.09 α-Fenchene 951 0.36 0.31 0.23 0.20 Camphene 955 0.57 0.45 0.32 0.22 Thuja-2,4(10)-diene 960 0.96 0.27 0.12 _ Sabinene 977 0.22 0.41 0.05 0.04 β-pinene 982 1.03 1.20 0.96 1.73 Myrcene 994 0.14 1.53 2.53 3.09 -Phellandrene 1005 _ _ 0.13 _ -3-Carene 1011 _ 0.15 1.87 2.14 α-Terpinene 1019 _ _ _ 0.05 p-Cymene 1027 0.46 0.26 _ 0.42 Limonene 1033 2.46 2.20 50.46 42.51 Z--Ocimene 1040 0.10 _ _ _ -Terpinene 1062 _ _ 0.11 0.25 α-Terpinolene 1088 0.25 0.79 0.24 0.94 α-Pinene oxide 1097 0.33 _ _ _ Linalool 1098 0.13 _ _ _ α-Campholenal 1127 1.31 0.30 0.15 _ trans-Pinocarveol 1141 2.85 0.92 0.36 _ Camphor 1143 _ _ _ 0.09 trans-Verbenol 1144 2.09 0.34 _ _ trans-Pinocamphone 1161 0.38 _ _ _ Pinocarvone 1168 _ 0.13 _ _ α-Phellandren-8-ol 1170 _ 0.28 _ _ Terpinene-4-ol 1179 0.11 0.31 0.25 0.08 p-Cymen-8-ol 1188 0.55 0.39 _ _ cis-Piperitol 1194 _ 0.86 0.28 0.15 Myrtenal 1197 0.47 _ _ _ Verbenone 1204 0.44 _ 0.13 _ trans-Carveol 1229 0.26 _ 0.50 _ cis-Carveol 1230 _ _ 0.14 _ Carvone 1242 _ _ 0.35 _ Bornyl acetate 1285 0.49 1.20 0.56 0.08 -Elemene 1339 _ 0.11 _ _ α-Copaene 1376 _ _ 0.49 _ -Bourbonene 1384 _ _ 0.16 _ -Elemene 1393 _ 0.18 0.29 0.12 β-Caroyophyllene 1418 _ 0.78 0.61 1.79 -Elemene 1430 _ 0.87 0.18 0.51 α-Humulene 1452 _ 0.10 0.50 2.11  -Gurjunene 1473 _ _ 0.17 _ Germacrene D 1480 _ 0.26 _ 0.79 -Selinene 1485 _ 0.39 0.73 0.11 α-Selinene 1493 _ 0.33 _ 0.23 α-Muurolene 1499 _ 0.16 0.30 0.08 α-Amorphene 1506 _ _ 0.32 0.08 -Cadinene 1512 _ 0.19 _ 0.34 -Cadinene 1516 _ 0.78 0.85 0.53 cis-Calamenene 1521 _ 0.26 0.94 0.21 Elemol 1547 _ 0.28 0.15 0.22 Germacrene B 1556 _ 1.19 0.23 0.68 Caryophylene oxide 1573 _ 0.53 0.33 0.50 α-Cedrol 1604 _ 0.84 _ _ COMPARISON OF CHEMICAL COMPOSITION AND ANTIOXIDANT ACTIVITY 11 -Cadinol 1636 _ _ _ 0.09 β-Eudesmol 1651 _ _ _ 2.16 α-Cadinol 1652 _ 0.19 _ _ Total identified (%) 97% 99% 98% 98% GC-MS analysis of the four oils of J. excelsa show some similarities and differences in their monoterpene and sesquiterpenes chemical composition. The essential oil of the gum-resin contains the lowest number of components (25 compounds) whilst the essential oil of the branches contains the highest number of components (39). Each one of the four oils contains twelve monoterpene hydrocarbons but they differ in the number of oxygenated monoterpenes. The four essential oils share 11 monoterpenes and differ in 24 monoterpenes. The identity of the major component also differs among the four oils; while the essential oils of the gum and branches contain α-pinene as the major compound (80.50% and 79.03% respectively) the oils of leaves and fruits contain limonene as the major component (50.46% and 42.51% respectively). In terms of composition of sesquiterpenes, the essential oils of leaves, branches and fruits contain varied proportions of sesquiterpenes while that of gum-resin contains no sesquiterpenes. Tricyclene Thujene Pinene Fenchene Camphene Thuja-2,4(10)-diene Sabinene Pinene Myrcene Phellandrene Carene Terpinene pCymene Limonene Z-Ocimene Terpinene Terpinolene Pinene O Linalool HO CHO Campholenal trans-Pinocarveol OH O Pinocarvone Phellandren-8-ol OH Terpinene-4-ol OH pCymene OH OH cis-Piperitol HO Myrtenal Verbenone O trans-Carveol HO cis-Carveol HO Carvone O Bornyl acetate O O Camphor O trans-Verbenol OH trans-Pinocamphone O Figure 1. Monoterpenes from the essential oils of the J. excelsa. SALEH N. AL-BUSAFI ET AL. 12 Elemene Elemene Elemene H H H Bourbonene H H Copaene H H Caroyophyllene Humulene H Gurjunene Germacrene D Selinene Selinene H H Murrolene H H Amorphene H H Cadinene H Cadinene cis-Calamenene OH Elemol Germacrene B H H Caryophylene oxide O Cedrol H OH Cadinol HO Eudesmol OH HH Cadinol HO Figure 2. Sesquiterpenes from the essential oils of the J. excelsa. 3.3 Total antioxidant activity The antioxidant activity of the essential oils of different parts of J. excelsa was evaluated by using the phosphomolybdenum method which is based on the reduction of Mo(VI) by the sample analyte and the subsequent formation of green phosphate Mo(V) complex with a maximum absorption at 695 nm. Total antioxidant activity of the four essential oils, expressed as ascorbic acid equivalent (mg of AA per g of the oil), was obtained from the calibration curve of ascorbic acid (AA) as shown in Figure 1. The essential oil of J. excelsa leaves showed higher total antioxidant activity compared to the other three oils scoring 385.0 mg ascorbic acid (AA) equivalents followed by the EO of gum- resin with total antioxidant activity of 277.0 mg (Figure 3). The EO of the fruits showed the lowest activity with 108.0 mg AA. COMPARISON OF CHEMICAL COMPOSITION AND ANTIOXIDANT ACTIVITY 13 Figure 3. Antioxidant activity of J. excelsa essential oil. 3.4 DPPH radical scavenging activities Another standard method to quantify antioxidant activity of essential oils is to measure their hydrogen donating ability to a DPPH radical. In this study, essential oils of different parts of J. excelsa were investigated for their radical scavenging activity and compared with that of ascorbic acid (AA) (Figure 4). The scavenging activity of the four essential oils, as well as that of ascorbic acid, increases as the concentration increases. The four oils, however, showed lower activity than ascorbic acid. Figure 5 exhibits the IC50 values which describe the concentration of antioxidant required to inhibit 50% of DPPH radicals. The smaller the IC50 value, the stronger the antioxidant activity obtained. The data obtained showed that the radical scavenging of the four essential oils decreased in the following order: leaves (IC50 = 20.47) > fruits (IC50 = 30.27) > resin-gum (IC50 = 36.77) > branches (IC50 = 40.46). Figure 4. DPPH radical inhibition activity of J. excelsa essential oils compared with ascorbic acid (AA) activity. a: Ascrorbic acid; b: J.excelsa leaves oil; c: J. excelsa branches oil; d: J. excelsa fruits oil; e: J.excelsa gum oil. 0 50 100 150 200 250 300 350 400 450 Leafs Gum Branches Fruits A n ti o x id a n t a c ti v it y 0 10 20 30 40 50 60 70 80 90 0 20 40 60 80 100 120 D P P H s ca ve n g in g Concentration a b c d e SALEH N. AL-BUSAFI ET AL. 14 Figure 5. IC50 values of ascorbic acid (AA) and J. excelsa essential oils. 4. Conclusion The chemical content and compositions of four essential oils extracted from resin-gum, leaves, branches and fruits of J. excelsa from Jabal Al-Akhdhar (Sultanate of Oman) were analyzed by the GC-MS method. The analysis showed some variations as well as similarities in their chemical contents and compositions. Out of a total of 35 different monoterpenes existing in the four essential oils, 11 monoterpenes are shared by the four oils. The essential oil of the resin-gum of J. excelsa is characterized by the absence of sesquiterpenespinene was found to be the major compound in the essential oil of resin-gum and branches with 80.50% and 79.03%, respectively, while limonene is the major compound in the essential oil of leaves and fruits with 50.46% and 42.51%, respectively. The essential oil of the leaves of J. excelsa shows stronger antioxidant activity and radical scavenging activity than other essential oils, but all four oils show lower antioxidant and radical inhibition activities when compared to ascorbic acid (AA). 5. Acknowledgment We acknowledge, with thanks, financial support from the Sultan Qaboos University. 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