The chemical components of the leaf oil of
Litsea
acutivena
Ha
yata
collected from Pù Huong Natural Reserve, Nghe
An Province
, Vietnam, were identified by co-chromatography with authentic samples, gas chromatography/mass spectrometry (GC/MS) and linear retention indices. The significant compounds of L. acutivena were
α
-phellandrene (30.4%) and α-
p
inene (14.2%).
The constituents of essential oil of L. acutivena from Vietnam are being reported for the first time.
The volatile compositions of some Vietnamese species of Litsea have reported recently. In our previous report [1] , we have identified limonene (17.5%), β-caryophyllene (14.2%), bicyclogermacrene (13.1%), bicycloelemene (12.4%) and α-phellandrene (8.0%) as the major constituents of the leaf oil of L. helferi. Likewise, the oil of L. ferruginea contained large amounts of sabinene (34.5%), α-pinene (10.1%), γ-terpinene (7.8%), limonene (6.9%) and terpinen-4-ol (6.6 %) while linalool (23.4%), α-pinene (26.1%) and β-pinene (11.7%) were the compounds occurring in large proportions in the leaf oil of L. verticillata. Moreover, (E)-β-ocimene (57.4%), was the significant compound in the leaf oil of L. glutinosa. In addition, (Z)-citral (32.9% - 66.1%), sabinene (1.4% - 14.2%), limonene (7.0% - 13.6%) and linalool (1.9% - 9.5%) were the main compounds in the leaf, stem, fruits and roots oils of L. cubeba [1] .
Phytochemical studies on L. acutivena revealed the characterization of dehydroxymethylailanthoidol, litseakolide D-G [2] , acutilactone [3] and 4-nonacosyl-dihydrofuran-2-one [3] . In a previous report [4] , the main volatile compounds of the leaf oil of L. acutivena were found to be γ-patchoulene (11.0%), δ-cadinene (6.3%), trans-muurola-3,5-diene (5.9%) and β-selinene (5.3%). However, the components occurring in higher quantity from the twig oil were characterised to be t-cadinol (13.1%), β-selinene (9.6%), trans-β-ocimene (6.2%) and α-cadinol (7.7%).
In continuation of our extensive research on the analysis of essential oils from Vietnamese flora [1] [5] [6] , this paper reports the volatile constituents of L. acutivena leaf oil.
2. Materials and Methods2.1. Plants Collection
The leaves of L. acutivena were collected from Pù Huống Natural Reserve, Nghệ An Province (19˚20'N 104˚50'E), Vietnam, in August 2014. Botanical identification was achieved by Dr. Nguyen Lam. A voucher specimen NTL384 was deposited at the Botany Museum, Vinh University, Vietnam.
2.2. Preparation of Plant Sample
Prior to hydrodisitillation, the leaves of L. acutivena were air-dried (17˚C, without washing with water) under laboratory shade for two weeks to reduce the moisture contents. In addition, sediments and other unwanted materials were separated from the samples. Afterwards, samples were pulverized to coarse powder using a locally made grinder.
2.3. Hydrodistillation of Essential Oil
A total of 500 g of the pulverized plant samples were used for the experiment at different time. Known weight of samples was separately and carefully introduced into a 5 L flask and distilled water was added until it covers the sample completely. Essential oils were obtained by hydrodistillation which was carried out in an all glass Clevenger-type distillation unit designed according to Vietnamese Pharmacopoeia [7] as described previously [1] [5] [6] . All experiments were done in triplicate. The distillation time was 3 h and conducted at normal pressure. The volatile oils distilled over water and were collected by running through the tap 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 described previously [1] [5] [6] .
2.4. Analysis of Essential Oil
The gas chromatography (GC) analysis of the essential oil was actualised using an Agilent Technologies HP 6890 Plus Gas chromatograph containing Flame Ionization Detector, fused with HP-5MS column (dimensions: 30 m × 0.25 mm; film thickness 0.25 μm). He (1 mL/min) was used as carrier gas. The inlet pressure was 6.1 kPa. The injector and detector temperatures were maintained at 250˚C and 260˚C respectively. The analysis was done by column temperature programmed starting from 40˚C (2 min hold) and ending at 220˚C (10 min hold) at 4˚C/min. The volume of the sample injected was 1.0 μL and injection was done at the split ratio of 10:1. Each analysis was performed in triplicate. The relative amounts of individual components were calculated based on the GC peak area (FID response).
For the experiment on gas-chromatograph-mass spectrometry analysis, a HP 6890N Plus gas chromatograph interfaced with a mass spectrometer HP 5973 MSD was used. The column employed was HP-5 MS (fused capillary, dimension: 30 m × 0.25 mm; film thickness 0.25 mm). The condition for the gas chromatograph was as described above. The conditions used for the Mass Spectrometry were ionization voltage of 70 eV, with mission current 40 mA. The acquisitions scan mass range of 35 - 350 amu at a sampling rate of 1.0 scan/s was maintained throughout the experiment.
2.5. Identification of Constituents of Essential Oil
The identification of constituents from the GC/MS spectra of L. acutivena was performed on the basis of retention indices (RI) determined with reference to a homologous series of n-alkanes (C4-C40), under identical experimental conditions. In some cases, co-injection with known compounds or standards (Sigma-Aldrich, St. Louis, MO, USA) under the same GC conditions was employed. The mass spectral (MS) fragmentation patterns were checked with those of other essential oils of known composition (NIST 08 Libraries) [8] and with those in the literature as described previously [1] [5] [6] .
3. Results and Discussion
The average yield of the essential oil was 0.16% ± 0.01% (v/w) calculated on a dry weight basis. Both oil samples were light yellow in colouration. All compounds are listed in order of their elution from the HP-5MS column (Table 1). From the results presented (Table 1) the 22 leaf oil constituents of L. acutivena were primarily monoterpenoids. Monoterpene hydrocarbons (62.0%) occurred in higher amounts with quantitative amounts of sesquiterpene hydrocarbons (17.9%) and oxygenated sesquiterpenes (11.3%). Among the monoterpenes, a-phellandrene (30.4%) and α-pinene (14.2%) were the major compounds. Previously, sesquiterpene compound predominated in the the leaf of L. acutivena from Taiwan [4] . Conversely, com pounds such as γ-patchoulene and trans-muurola-3,5-diene described from Taiwanese oil were not identified in the Vietnamese sample. In addition, the quantity of α-phellandrene and α-pinene in the Taiwanese oils [4] are lower when compared with data obtained in the present study.
Compounds identified in the essential oil of L. acutivena
Sr. No.
Compoundsa
RIb
RIc
Percent compositiond
1
α-Pinene
939
932
14.2
2
β-Pinene
980
978
7.3
3
Myrcene
990
988
1.2
4
a-Phellandrene
1006
1004
30.4
5
p-Cymene
1024
1020
3.4
6
β-phellandrene
1028
1026
1.8
7
Limonene
1032
1030
1.7
8
(Z)-β-Ocimene
1043
1034
1.1
9
γ-Terpinene
1061
1056
0.9
10
Linalool
1100
1100
4.8
11
(Z)-Citral
1318
1318
1.1
12
b-Caryophyllene
1419
1417
3.8
13
Aromadendrene
1440
1439
1.2
14
allo-Aromadendrene oxide
1456
1458
0.9
15
a-Patchoulene
1457
1460
2.4
16
Guaia-1(10),11-diene
1490
1490
5.7
17
(E,E)-α-Farnesene
1508
1505
4.8
18
Ledol
1569
1570
1.4
19
α-Guaiol
1600
1600
1.5
20
β-Acorenol
1637
1640
1.7
21
7(11)-Selinen-4α-ol
1693
1694
4.1
22
Zerumbone
1756
1760
1.7
Total
97.1
Monoterpene hydrocarbons (Sr. No. 1 - 9)
62
Oxygenated monoterpenes (Sr. No. 10 and 11)
5.9
Sesquiterpene hydrocarbons (Sr. No. 12 - 17)
17.9
Oxygenated sesquiterpenes (Sr. No. 18 - 22)
11.3
aElution order on HP-5MS column; bRetention indices on HP-5MS column; cLiterature retention indices (NIST, 2011); dStandard deviation (SD±) were insignificant and were excluded from the Table; Sr. No. serial Number.
Monoterpene compounds were the main classes of compounds occurring in higher quantity in Vietnamese oil sample as against the sesquiterpenoids found in Taiwnaese oil [4] . These results demonstrate significant regional variation in the chemical composition of L. acutivena.
The chemical composition of essential oils of Litsea plants can be classified according to class of compounds they contained. Recent information showed that the compositions of the oils of L. ferruginea, L. verticillata, L. cubeba and L. glutinosa [1] were dominated by monoterpene compounds like the oils of L. acutivena in the present study. The monoterpenes neral and geranial [9] and γ-terpinene [10] were the main constituents of essential oils of L. cubeba from China and several other parts of the world [1] . Likewise the monoterpene 1,8-cineole was present in L. pungens [10] while L. akoensis leaf oil limonene, thymol and p-cymene with β-phellandrene and trans-β-ocimene present in the twig oil [11] . It could be seen that the main monoterpene components of the individual species differed from each other. The leaf oils of L. helferi had abundance of sesquiterpene compounds including β-caryophyllene, bicyclogermacrene and bicycloelemene [1] while γ-patchoulene, δ-cadinene and trans-muurola-3,5-diene occurred in higher amounts in L. acutivena [4] . The main sesquiterpene compounds identified in L. glutinosa [12] were β-caryophyllene and bicyclogermacrene with α-humulene and δ-cadinene making up the major components of L. nakaii [13] . Previously the sesquiterpenes β-eudesmol, γ-eudesmol and δ-selinene were identified in L. kostermansii [14] while L. acuminata [15] contained β-caryophyllene, τ-cadinol, α-cadinol and α-humulene. The main components of the leaf oil of L. linii were β-eudesmol, t-cadinol and α-humulene [16] . However, L. mushaensis leaf oil contained higher amounts of β-selinene, α-selinene and β-caryophyllene [16] . As usual, the identities of the major sesquiterpene components of the individual species differed from one another. Also, mixture of monoterpene and sesquiterpene compounds (trans-β-ocimene and β-selinene) characterized the essential oil of the twig of L. mushaensis [16] . The compositions of essential oil of L. coreana leaf was domainted mainly by mixture of sesquiterpene compounds and fatty acids namely n-decanal, (2E, 6E)-farnesol, β-eudesmol and ethyl n-dodecanoate [17] . It can be postulated that both intra and inter species variation could be observed in the essential oils of Litsea plants.
4. Conclusion
The paper reported the compounds identified in the essential oils of L. acutivena grown in Vietnam. The significant compounds of the oil were α-phellandrene and α-pinene. In addition, a comparative analysis of the composition of the essential oils was performed with results from the same species reported elsewhere and other species reported from Vietnam as well as Litsea plants grown in other parts of the world. The results indicated differing compositional pattern with the same species and other species.
Acknowledgements
This research is funded by Vietnam National Foundation for Science and Technology Development (NAFOSTED) under grant number: 106.03-2018.02.
Conflicts of Interest
The authors declare no conflicts of interest regarding the publication of this paper.
Cite this paper
Dai, D.N., Lam, N.T.T., Dung, N.A., Huong, L.T., Chau, D.T.M. and Ogunwande, I.A. (2019) Composition of Essential Oils from Litsea acutivena Hayata. American Journal of Plant Sciences, 10, 615-621. https://doi.org/10.4236/ajps.2019.104044
ReferencesSon, L.C., Dai, D.N., Thang, T.D., Huyen, D.D. and Ogunwande, I.A. (2014) Analysis of Essential Oils from Five Vietnamese species of Litsea (Lauraceae). Journal of Essential Oil-Bearing Plants, 17, 960-971.
https://doi.org/10.1080/0972060X.2014.935068Cheng, H.I., Lin, W.Y., Duh, C.Y., Lee, K.H., Tsai, I.L. and Chen, I.S. (2001) New Cytotoxic Butanolides from Litsea acutivena. Journal of Natural Product, 64, 1502-1505. https://doi.org/10.1021/np0102298Tsai, I.L., Cheng, M.J., Hung, H.W., Cheng, H.I. and Chen, I.S. (2007) Chemical Constituents from the Leaves of Litsea acutivena. Journal of Chinese Chemical Society, 54, 503-506. https://doi.org/10.1002/jccs.200700071Ho, C.L., Liao, P.C., Wang, E.I. and Su, Y.C. (2011) Composition and Antimicrobial Activity of the Leaf and Twig oils of Litsea acutivena from Taiwan. Natural Product Communications, 6, 1755-1758. https://doi.org/10.1177/1934578X1100601145Chinh, H.V., Luong, N.X., Thin, B.D., Dai, D.N., Hoi, T.M. and Ogunwande, I.A. (2017) Essential Oils of the Leaves of Cinnamomum glaucescens (Nees) Drury and Cinnamomum verum Presl from Vietnam. American Journal of Plant Sciences, 8, 2712-2721. https://doi.org/10.4236/ajps.2017.811182Hoi, T.M., Dai, D.N., Ha, C.T.T., Anh, H.V. and Ogunwande, I.A. (2019) Essential oil Constituents from the Leaves of Anoectochilus setacues, Codonopsis javanica and Aristiochia kwangsiensis from Vietnam. Records of Natural Product, 13, 281-286. https://doi.org/10.25135/rnp.103.18.08.124(1997) Vietnamese Pharmacopoeia. Medical Publishing House, Hanoi.NIST (2011) Chemistry Web Book. Data from NIST Standard Reference DatabaseVietnamese Pharmacopoeia.Si, L., Chen, Y., Han, X., Zhan, Z., Tian, S., Cui, Q. and Wang, Y. (2012) Chemical Composition of Essential Oils of Litsea cubeba Harvested from Its Distribution Areas in China. Molecules, 17, 7057-7066.
https://doi.org/10.3390/molecules17067057Zhili, J., Yasmin, A., Rod, B., Xing, Z. and Isman, M.B. (2009) Comparative Toxicity of Essential Oils of Litsea pungens and Litsea cubeba and Blends of Their Major Constituents against the Cabbage Looper, Trichoplusia ni. Journal of Agriculture and Food Chemistry, 57, 4833-4837. https://doi.org/10.1021/jf900274rHo, C.L., Lin, C.Y., Wang, E.I. and Su, Y.C. (2011) Composition, Antioxidant and Antimicrobial Activities of Leaf and Twig Essential Oils of Litsea akoensis from Taiwan. Natural Product Communications, 6, 901-904.
https://doi.org/10.1177/1934578X1100600634Hien, N.T., Thang, T.D., Do, N.D. and Tran, H.T. (2010) Chemical Composition of the Leaf Oil of Litsea glutinosa (Lour.) C. B. Rob. from Ha Tinh Province. Journal of Science Natural Science and Technology Vinh National University, 26, 161-164.Ho, C.L., Wang, E.I., Lee, P.Y. and Su, Y.C. (2009) Composition and Antimicrobial Activity of the Leaf Essential Oil of Litsea nakaii from Taiwan. Natural Product Communications, 4, 865-868. https://doi.org/10.1177/1934578X0900400626Ho, C.L., Wang, E.I., Hsu, K.P., Lee, P.Y. and Su, Y.C. (2009) Composition and Antimicrobial Activity of the Leaf Essential Oil of Litsea kostermansii from Taiwan. Natural Product Communications, 4, 1123-1126.Su, Y.C. and Ho, C.L. (2013) Composition and Two Activities of the Leaf Essential Oil of Litsea acuminata (Blume) Kurata from Taiwan. Records of Natural Product, 7, 27-34.Ho, C.L., Liao, P.C., Tseng, Y.H., Wang, E.I.C. and Su, Y.C. (2009) Composition and Antimicrobial Activity of the Leaf and Twig Oils of Litsea mushaensis and L. linii from Taiwan. Natural Product Communications, 5, 1783-1788.Ho, C.L., Hsu, K.P., Tseng, Y.H., Liao, P.C., Wang, E.I., Jeyashoke, N., et al. (2010) Composition and Antifungal Activities of the Leaf Essential Oil of Litsea coreana from Taiwan. Natural Product Communication, 5, 1677-1680.
https://doi.org/10.1177/1934578X1000501033