Cinnamomum glaucescens (Nees) Hand.-Mazz is an evergreen tree where the buds are enclosed in overlapping scales. The leaves are about 7 - 10 cm long placed on stalks which is about 1 - 2 cm long. The inflorescences are covered with brown hairs. The fruits are 3 cm long   . The major compounds present in the fruit oil of C. glaucescens  were 1,8-cineole (13%) and methyl cinnamate (14%), while 1,8-cineole (56%) and α-terpineol (10%) were found in the pericarp oil. In another report, methyl (E)-cinnamate (40.5%) and 1,8-cineole (24.5%) were also identified in the fruit oil of C. glaucescens  . 1,8-Cineole (43.6%) and elemicin (92.9%) were described in the fruit  and leaf  oils respectively. The nematicidal, termiticidal, mosquito larvicidal  , insecticidal, antifungal, antiaflatoxin, antioxidant  and antibacterial  activities of essential oils of C. glaucescens have been reported.
Cinnamomum verum J.S. Presl is an evergreen tree that grows up to 18 m tall. The fruits are black when ripe and surrounded by the enlarged perianth at the base  . The various ethanol extracts of C. verum were reported to possessed high analgesic  , antifungal     , anti-tuberculosis  , antioxidant    and antihyperglycaemic  properties. 2-Methoxycinnamaldehyde, a component of C. verum was described as a potential anticancer agent   . The chemical constituents characterized from the methanolic extracts  of C. verum were trans-cinnamaldehyde (20.28%), (E)-3-(2-methoxyphenyl)-2-propenoic acid (40.41%) and 4-vinyl benzoic acid (10.54%).
Various authors have described different main compounds (chemotypes) of essential oils of C. verum. These include eugenol type     , safrole type  , cinnamaldehyde and isomers type   -  , (E)-cinnamaldehyde/ eugenol/linalool type  , cinnamyl acetate type  and benzyl benzoate type  . The essential oils of C. verum were reported to displayed antibacterial      , nematicidal  , antifungal, anti-elastase and anti-keratinase  and anti-rot  activities. Cinnamaldehyde, one of major compounds of C. verum oil exhibited antibacterial  and anthelmintic  properties. The biofungicides action  and the efficacy of C. verum essential oil as an acaricidal agent against Rhipicephalus microplus larvae was reported  . The oil had a protective effect on experimental Streptococcosis iniae infection in tilapia  . Moreover, the oil showed mosquito knock-down and adulticidal activities against Culex quinquefasciatus  .
In the present paper, the results of our studied on the phytochemicals in the essential oils of Vietnamese species of C. verum and C. glaucescens were reported. Previously, the phytochemical constituents of some other plants have been characterized and reported  .
2. Materials and Methods
2.1. Plant Samples
The leaf samples of C. glaucescens and C. verum were collected from Bến En National park, Thanh Hóa Province, Vietnam, in August 2013. Voucher specimens HVC 377 and HVC 04 respectively were deposited at the HN, Vietnam. The drying of the plant samples was accomplished by exposure to air under laboratorys shade for two weeks.
2.2. Hydrodistillation of Essential Oils
Aliquots of 500 g air-dried and pulverized samples individually subjected to hydrodistillation process which was carried out in an all glass Clevenger-type distillation unit designed according to the established specification  . The distillation time was 3 h and conducted at normal pressure. The volatile oils distilled over water and were collected in the receiver arm of the apparatus into clean and previously weighed sample bottles. The oils were kept under refrigeration (4˚C) until the moment of analyses as previously described  .
2.3. Gas Chromatography (GC) Analysis
The GC analysis was carried out on HP 6890 Plus Gas chromatograph (Agilent Technologies) equipped with a flame ionization detector (FID). The column used was HP-5MS column with the dimension 30 m × 0.25 mm (film thickness 0.25 mm). Temperature programming parameters: column oven―40˚C, injection pot―250˚C, detector―300˚C. Time programming: 40˚C for 2 min, temperature raised to 220˚C (10 min hold) at 4˚C/min. Carrier gas used was H2 (flow rate of 1 mL/min), split ratio 10:1, volume injected―1.0 mL. Inlet pressure was 6.1 kPa. Retention indices (RI) value of each component was determined relative to the retention times of a homologous n-alkane series (C4-C32) with linear interpolation on the HP-5MS column. Relative percentage amounts were computed from GC peak areas without FID response factor correction as previously described  .
2.4. Gas Chromatography/Mass Spectrometry (GC/MS) Analysis
The GC/MS experiment was performed on Mass spectrometer (HP 5973 MSD) combined with HP 6890N Plus GC. The system was fitted with HP-5 MS capillary column of 30 m × 0.25 mm having film thickness of 0.25 mm. All operating conditions were similar to that of GC except that He (1 mL/min) was the carrier gas. The Mass Spectrometer was operated on the following conditions: ionization voltage (70 eV), emission current (40 mA) and acquisitions scan (mass range of 35 - 350 amu). The sampling rate was 1.0 scan/s as previously described  .
2.5. Identification of Constituents of Essential Oils
The compounds present in the oil samples were identified by comparing the individual relative retention indices with standards obtained from pure compounds. In addition, comparison was made with values from literature under the similar experimental conditions  and as previously described  .
3. Results and Discussion
The percentage yields of essentials oils obtained from the extraction processes were 0.42% (v/w, C. glaucescens) and 0.45% (v/w, C. verum). The colours of the essential oils were determined as light yellow. The compounds that were identified in the samples could be seen in Table 1 with detailed analysis of their retention indices and percentage compositions. Monoterpene hydrocarbons (25.9%) and oxygenated monoterpenes (64.3%) were determined as the dominant class of compounds of C. glaucescens oil. the main constituents of the oil were geraniol
Table 1. Volatile compounds present in the essential oils of C. galucescens and C. verum.
aCompounds order of elution from HP-5MS column; RI (cal.) Calculated retention indices of each compounds on HP-5MS column; RI (Lit.) Literature retention indices; -not identified.
(36.2%) and terpinen-4-ol (19.7%). α-Pinene (6.0%), sabinene (6.0%) and limonene (5.2%). Sesquiterpne compounds were present in amount < 1%. Except for α-terpineol, all other known compounds such as 1,8-cineole and methyl cinnamate   , α-terpineol  , (E)-cinnamate  and elemicin  that were previously identified in the essential oil of C. glaucescens were not present in the present oil sample. On the other hand, the present oil sample contained large quantities of geraniol and terpinen-4-ol which were not identified in previously studied oil samples of C. glaucescens.
In the present study, sesquiterpene hydrocarbons (30.0%), oxygenated monoterpenes (29.5%), oxygenated sesquiterpenes (18.8%) and monoterpene hydrocarbons (12.5%) were the classes of compounds present in C. verum. The major constituents of the oil were mainly linalool (22.0%) and bicyclogermacrene (11.2%). Additionally, β-bisabolene (7.7%), caryophyllene oxide (5.6%) and g-cadinene (4.0%) were also present in the oil in significant amount.
A comparative analysis of the present oil of C. verum and previous studies            indicated great variations in their chemical compositions. Several of the compounds that were present in the previously investigated oil samples were not identified in the present oil sample and vice versa. For example, the present oil of C. verum contained lower quantity of eugenol and benzyl benzoate when compared with previous results     . In addition, compounds such as (E)-cinnamaldehyde        and cinnamyl acetate  that were described previously as main compounds of C. veum oil, were not obtained in the oil sample. However, the amount of linalool in the present C. veum oil was in agreement with previously investigated oil sample  . A noteworthy observation is that bicyclogermacrene, a main compound in the present C. veum oil was not described to be a significant compound in previously investigated samples of C. verum oils.
Several reports describing the chemical compositions of essential oils from some Vietnamese species of Cinnamomum have been published. In summary, each of the essential oils possessed compounds that were different from the other oil samples. The main compounds in the essential oil of C. sericans  were spathulenol (14.5%) and caryophyllene oxide (9.3%), while ρ-cymene (15.6%), limonene (13.9%) and α-phellandrene (9.2%) were found C. durifolium  . However, bicyclogermacrene (33.9%) and β-caryophyllene (25.5%) make up the composition of C. magnificum  . The essential oil of C. iners  consisted mainly of β-caryophyllene (35.9%) and caryophyllene oxide (12.6%). The leaf oil of C. curvifolium contained high contents of benzyl cinnamate and benzyl benzoate  . Interestingly, a-selinene ((24.5%) and β-caryophyllene (23.0%) were the major volatiles of C. rigidifloim  .
From the chemotaxonomy point of view, C. verum in the present study contained linalool which was also found to be the dominant compound of essential oils of C. damhaensis and C. cambodianum from Vietnam  . However, the essential oils of most Cinnamomum species from Vietnam possessed low content of (E)-cinnamaldehyde   when compared with other samples analyzed from other parts of the world.
The paper reported the compounds identified in the essential oils of C. verum and C. glaucescens grown in Vietnam. The significant compounds of C. glaucescens were geraniol and terpinen-4-ol whil, C. verum comprised of linalool and bicyclogermacrene. In addition, a comparative analysis of the composition of the essential oils was performed with results from other species reported from Vietnam as well as Cinnamomum plants grown in other parts of the world. More studied will be required in order to be able to delineate the various chemotypes of essential oils of Cinnamomum plants in various parts of the world.
Authors are grateful to Mrs. Musilimat Ogunwande for the typesetting of the manuscript.
 Adhikary, S.R., Tuladhar, B. S., Sheak, A., van Beek, T.A., Posthumus, M.A. and Lelyveld, G.P. (1992) Investigation of Nepalese Essential Oils. I. The Oil of Cinnamomum glaucescens (Sugandha Kokila). Journal of Essential Oil Research, 4, 151-159.
 Satyal, P., Paudel, P., Poudel, A., Dosoky, N.S., Pokharel, K.K. and Setzer, W.N. (2013) Bioactivities and Compositional Analyses of Cinnamomum Essential Oils from Nepal: C. camphora, C. tamala and C. glaucescens. Natural Product Communications, 12, 1777-1784.
 Prakash, B., Priyanka, S., Shilpee, Y., Singh, S.C. and Dubey, N.K. (2013) Safety Profile Assessment and Efficacy of Chemically Characterized Cinnamomum glaucescens Essential Oil against Storage Fungi, Insect, Aflatoxin Secretion and as Antioxidant. Food and Chemical Toxicology, 53, 160-167.
 Baruah, A. and Nath, S.C. (2006) Leaf Essential Oils of Cinnamomum glanduliferum (Wall) Meissn and Cinnamomum glaucescens (Nees) Meissn. Journal of Essential Oil Research, 18, 200-202.
 Rajendra, G., Jyoti B., Shiksha, A., Esha, P., Udaya, L.P., Ranjana, P., Rajan, S. and Tritha, M.S. (2013) Antibacterial and Cytotoxic Activities of High Altitude Essential Oils from Nepalese Himalaya. Journal of Medicinal Plant Research, 7, 738-743.
 Minakshi, P. and Chandrai, D.R. (2015) Evaluation of Ethanol and Aqueous Extracts of Cinnamomum verum Leaf Galls for Potential Antioxidant and Analgesic activity. Indian Journal of Pharmaceutical Science, 77, 243-247.
 Monir, D., Mahbubeh, S. and Zahra, R. (2016) Effects of Aqueous Extract of Cinnamomum verum on Growth of Bread Spoilage Fungi. International Journal of Medical Research & Health Sciences, 5, 162-171.
 Mariappan, P.M., Gokulshankar, S., Babu, K., Sudha, J. and Navin, K.S. (2013) Chemical Characterisation and Antifungal Activity of Methanolic Extract of Cinnamomum verum J. Presl Bark against Malassezia spp. Pharmacognosy Journal, 5, 197-204.
 Moharm, B.A., Jantan, I., Jacinta, S. and Jamia, A.J. (2005) Antifungal Activity of the Bark and Leaf Oils of Cinnamomum verum J.S. Presl. Alone and in Combination against Various Fungi. Journal Sains Kesihatan Malaysia, 3, 1-12.
 Shashikant, V., Jaishankar, S., Jinesh, M., Nikita, P., Mubina, M., Suvarna, J.P. and Abhay, C. (2016) Assessment of Anti-Tuberculosis Activity of Extracts of Cinnamomum verum and Solanun surattense along with Isoniazid. European Respiratory Journal, 48, PA2691.
 Ofentse, M., Kabo, W., Tebogo, E.K., Shetonde, O.M. and Bokolo, M.K. (2015) Cinnamomum verum: Ethylacetate and Methanol Extracts Antioxidant and Antimicrobial Activity. Journal of Medicinal Plants Studies, 3, 28-32.
 Kirkham, S., Akilen, R., Sharma, S. and Tsiami, A. (2009) The Potential of Cinnamon to Reduce Blood Glucose Levels in Patients with Type 2 Diabetes and Insulin Resistance. Diabetes, Obesity and Metabolism, 11, 1100-1113.
 Tsai. K.D., Jonathan, C., Liu, Y.H., Chen, T.W., Wong, H.Y., Yang, S.M., Chou, K.S. and Cherng, J.M. (2016) Cinnamomum verum Component 2-Methoxycinnamaldehyde: A Novel Antiproliferative Drug Inducing Cell Death through Targeting Both Topoisomerase I and II in Human Colorectal Adenocarcinoma COLO 205 Cells. Food & Nutrition Research, 60, 31607.
 Wong, H.Y., Tsai. K.D., Liu, Y.H., Yang, S.M., Chen, T.W., Jonathan, C., Chou, K.S., Chang, C.M., Yao, B.T. and Cherng, J.M. (2016) Cinnamomum verum Component 2-Methoxycinnamaldehyde: A Novel Anticancer Agent with Both Anti-Topoisomerase I and II Activities in Human Lung Adenocarcinoma A549 Cells in Vitro and in Vivo. Phytotherapy Research, 30, 331-340.
 Patel, K., Sadaquat, A., Subramanium, S. and Dufour, J.P. (2007) Composition of the Leaf Essential Oil of Cinnamomum verum (Lauraceae) from Fiji Islands. Journal of Essential Oil Bearing Plants, 10, 374-377.
 Li, Y., Dexin, K., Lin, X.M., Xie, Z.H., Bai, M., Huang, S., Nian, H. and Hong, W. (2016) Quality Evaluation for Essential Oils of Cinnamomum verum Leaves at Different Growth Stages Based on GC-MS, FTIR and Microscopy. Food Analytical Methods, 9, 202-212.
 Siti, Y.M.S., Jamal, J.A., Husain, K. and Manshoor, N. (2013) Characterisation of Leaf Essential Oils of Three Cinnamomum Species from Malaysia by Gas Chromatography and Multivariate Data Analysis. Pharmacognosy Journal, 5, 22-29.
 Koketsu, M., Gonçalves, S.L., de Oliveira, G.R.L., Lopes, D. and Morsbach, N. (1997) The Bark and Leaf Essential Oils of Cinnamon (Cinnamomum verum Presl) Grown at Parana, Brazil. Food Science and Technology, 17, 281-285.
 Yap, P.S., Krishnan, T., Chan, K.G. and Lim, S.H. (2015) Antibacterial Mode of Action of Cinnamomum verum Bark Essential Oil, Alone and in Combination with Piperacillin, against a Multi-Drug-Resistant Escherichia coli Strain. Journal of Microbiology and Biotechnology, 25, 1299-1306.
 Okhee, C., Cho, S.K., Junheon, K., Chung, G.P. and Jinwoo, K. (2016) In Vitro Antibacterial Activity and Major Bioactive Components of Cinnamomum verum Essential Oils against Cariogenic Bacteria, Streptococcus mutans and Streptococcus sobrinus. Asian Pacific Journal of Tropical Biomedicine, 6, 308-314.
 Vazirian, M., Alehabib, S., Jamalifar, H., Fazeli, M.R., Najarian, T.A. and Khanavi, M. (2015) Antimicrobial Effect of Cinnamon (Cinnamomum verum J. Presl) Bark Essential Oil in Cream-Filled Cakes and Pastries. Research Journal of Pharmacognosy, 2, 11-16.
 Nagy, G., Hochbaum, T., Sárosi, S. and Ladányi, M. (2014) In Vitro and in Planta Activity of Some Essential Oils against Venturia inaequalis (Cooke) G. Winter. Notulae Botanicae Horti Agrobotanici Cluj-Napoca, 42, 109-114.
 Rattanachaikunsopon, P. and Phumkhachorn, P. (2010) Potential of Cinnamon (Cinnamomum verum) Oil to Control Streptococcus iniae Infection in Tilapia (Oreochromis niloticus). Fisheries Science, 76, 287-293.
 Park, I.K., Park, J.U., Kim, K.H., Choi, K.S., Choi, I.H., Kim, C.S. and Shin, C.S. (2005) Nematicidal Activity of Plant Essential Oils and Components from Garlic (Allium sativum) and Cinnamon (Cinnamomum verum) Oils against the Pine Wood Nematode (Bursaphelenchus xylophilus). Nematology, 7, 767-774.
 Monteiro, I.N., dos Santos, M.O., Costa-Junior, L.M., da Silva, L.A., de Aguiar Andrade, E.H., Maia, J.G.S. and Filho, V.E.M. (2017) Chemical Composition and Acaricide Activity of an Essential Oil from a Rare Chemotype of Cinnamomum verum Presl on Rhipicephalus microplus (Acari: Ixodidae). Veterinary Parasitology.
 Bouhdid, S., Abrini, J., Amensour, M., Zhiri, A., Espuny, M.J. and Manresa, A. (2010) Functional and Ultrastructural Changes in Pseudomonas aeruginosa and Staphylococcus aureus Cells Induced by Cinnamomum verum Essential Oil. Journal of Applied Microbiology, 109, 1139-1149.
 Al-Mariri, A., Saour, G. and Hamoud, R. (2012) In Vitro Antibacterial Effects of Five Volatile Oil Extracts against Intramacrophage Brucella Abortus 544. Iran Journal of Medical Science, 37, 119-125.
 Naveed, R., Hussain, I., Mahmood, M.S. and Akhtar, M. (2013) In Vitro and In Vivo Evaluation of Antimicrobial Activities of Essential Oils Extracted from Some Indigenous Spices. Pakistan Veterinary Journal, 33, 413-417.
 Anoosheh, S., Mona, S. and Akram, T. (2016) Evaluation of Antimicrobial Effect of Cinnamomum verum Methanolic Extract and Essential Oil: A Study on Bio-Preservative in Ketchup Sauce. Journal of chemical Health Risks, 6, 113-114.
 Sajjad, M., Khan, A. and Ahmad, I. (2011) In Vitro Antifungal, Anti-Elastase and Anti-Keratinase Activity of Essential Oils of Cinnamomum-, Syzygium- and Cymbopogon-Species against Aspergillus fumigates and Trichophyton rubrum. Phytomedicine, 19, 48-55.
 Okhee, C., Su, K.C. and Jinwoo, K. (2016) Biological Evaluation of 32 Different Essential Oils against Acidovorax citrulli, with a Focus on Cinnamomum verum Essential Oil. African Journal of Biotechnology, 15, 68-76.
 Williams, A.R., Ramsay, A., Hansen, T.V.A, Ropiak, H.M., Mejer, H., Nejsum, P., Mueller-Harvey, I. and Thamsborg, S.M. (2015) Anthelmintic Activity of Trans-Cinnamaldehyde and A- and B-Type Proanthocyanidins Derived from Cinnamon (Cinnamomum verum). Scientific Reports, 5, 14791.
 Ramar, M., Ignacimuthu, S. and Paulraj, M.G. (2014) Mosquito Knock-Down and Adulticidal Activities of Essential Oils by Vaporizer, Impregnated Filter Paper and Aerosol Methods. International Journal of Mosquito Research, 1, 26-32.
 Son, L.C., Dai, D.N., Thai, T.H., Huyen, D.D., Thang, T.D. and Ogunwande, I.A. (2013) The Leaf Essential Oils of Four Vietnamese Species of Cinnamomum (Lauraceae). Journal of Essential Oil Research, 25, 267-271.
 Son, L.C., Dai, D.N., Thai, T.H., Huyen, D.D., Thang, T.D. and Ogunwande, I.A. (2014) Study on Cinnamomum Oils: Compositional Pattern of Seven Species Grown in Vietnam. Journal of Oleo Science, 63, 1035-1043.