Essential oil composition of four Psiadia species from Reunion Island: A chemotaxonomic study

  • Published on
    04-Sep-2016

  • View
    216

  • Download
    4

Transcript

  • Essential oil composition of fourPsiadia species from ReunionIsland: A chemotaxonomic

    study

    Anne Gauvin *, Jacqueline Smadja

    Laboratoire de Chimie des Substances Naturelles et des Sciences des Aliments,

    Faculte des Sciences et Technologies, Universite de la Reunion,

    15 Avenue Rene Cassin, BP 7151, St Denis Messag Cedex 9,

    La Reunion 97 715, France

    Received 5 May 2004; accepted 24 December 2004

    Abstract

    The essential oils of four wild species of Psiadia (Psiadia anchusifolia, Psiadia argentea,Psiadia boivinii, Psiadia salaziana; Asteraceae) endemic to Reunion Island were obtained byhydrodistillation and subjected to detailed GC/MS analysis in order to determine possiblesimilarities among them and also the dierences in their chemical compositions depending on

    the stage of the life cycle (vegetative and owering). A total of 57 compounds were identiedincluding two unusual components 7,7-dimethyl-2-methylenebicyclo[3.3.1]heptan-6-ol acetate(1) and 6,6,8,9-tetramethyltricyclo[3.3.3.0]-undec-7-en-2-ol (2) which, until now, have been

    found only in species of the genus Psiadia. For P. anchusifolia, P. argentea and P. salaziana,the qualitative and quantitative composition of the oils appeared to be constant in the dierent

    Biochemical Systematics and Ecology 33 (2005) 705e714

    www.elsevier.com/locate/biochemsyseco* Corresponding author. Tel.: C33 262 262 938197; fax: C33 262 262 938183.E-mail address: gauvin@univ-reunion.fr (A. Gauvin).

    0305-1978/$ - see front matter 2005 Elsevier Ltd. All rights reserved.doi:10.1016/j.bse.2004.12.013

  • stages of their development. In contrast, considerable dierences were found to exist in thecomposition of essential oils of P. boivinii.

    2005 Elsevier Ltd. All rights reserved.

    Keywords: Psiadia anchusifolia; Psiadia argentea; Psiadia boivinii; Psiadia salaziana; Asteraceae; Essential

    oil composition; 7,7-Dimethyl-2-methylenebicyclo[3.3.1]heptan-6-ol acetate; 6,6,8,9-Tetramethyltricyclo-

    [3.3.3.0]-undec-7-en-2-ol; Chemotaxonomy

    1. Introduction

    The genus Psiadia Jacq. (Asteraceae) includes more than 60 species (Bosser et al.,1993; Scott, 1991). One species can be found in Sri Lanka and Southern India;several species are native to Arabia, East and South Africa, with a single species, nowextinct, formerly found in St Helena. This genus is also particularly well representedin Madagascar with 28 species and in the Mascarene Islands (Reunion, Mauritius,Roderick) with 26 species.

    Psiadia species are of particular interest as some of them are commonly used intraditional pharmacopoeia. Therefore, many papers about the secondary metabolitesof Psiadia species can be found in the literature (Abou-Zaid et al., 1991; Al-Yahyaet al., 1987; Canonica et al., 1967, 1969a,b; El-Domiaty et al., 1993; El-Feraly et al.,1990; Fortin et al., 2001; Jakobsen et al., 2001; Juma et al., 2001; Midiwo et al., 1997;Mossa et al., 1992; Robin et al., 1998; Wang et al., 1989a,b, 1992). The volatileconstituents of a few species have also been examined, for example, Psiadia altissima(Ramanoelina et al., 1994), Psiadia arabica (Mekkawi et al., 1984; Mossa et al.,1983), Psiadia arguta (Gurib-Fakim et al., 2000), Psiadia lithospermifolia(Gurib-Fakim et al., 1995), Psiadia salviifolia (Dennis, 1973), and Psiadia viscosa(Gurib-Fakim et al., 1995).

    As part of our research on the aromatic Psiadia of the Mascarenes (Gurib-Fakimet al., 2000; Gauvin et al., 2004), we report on the chemical composition of thevolatile oils obtained from Psiadia anchusifolia, Psiadia argentea, Psiadia boivinii,and Psiadia salaziana collected during the owering and vegetative phases inReunion Island, for comparison and for chemotaxonomic purposes. As far as weknow, the volatile constituents of these four Psiadia species endemic to ReunionIsland, have not been previously investigated.

    2. Material and methods

    2.1. Plant material

    The plant materials, collection places, dates and plant life-cycle stages (vegetative;owering) are given in Table 1. The plants were identied by Pr. DominiqueStrasberg and voucher specimens have been deposited in the herbarium of Reunion

    706 A. Gauvin, J. Smadja / Biochemical Systematics and Ecology 33 (2005) 705e714Island (REU).

  • 2.2. Sampling and essential oil extraction

    Sampling of the four species of Psiadia was done by a randomised collection of10e15 individuals. For each development stage (vegetative, owering), the essentialoils were isolated two times from 2! 500 g of the fresh leaves or the fresh aerialparts of the plants by hydrodistillation for 4 h using a modied Clevenger apparatus.The oils were taken up in dichloromethane, dried over anhydrous sodium sulphateand kept at 4 C. Yields of essential oil are reported in Table 1.

    2.3. Gas chromatographyemass spectrometry analyses

    GCeMS analyses were carried out using a HewlettePackard chromatograph type6890 series coupled to an HP 6890 mass selective detector. The MS detector was usedin the EI mode with an ionization voltage of 70 eV. Two capillary columns were usedunder the following conditions: (i) HP-5MS (30 m! 0.25 mm i.d., lm thickness:0.25 mm); oven temperature programme 60 C rising at 4 C/min to 200 C, held for30 min; ion source temperature, 280 C; injector temperature, 250 C; split ratio,1:20; carrier gas, helium; ow rate, 1.1 mL/min. (ii) Supelcowax (60 m! 0.20 mmi.d., lm thickness: 0.20 mm); oven temperature programme 60 C rising at 4 C/minto 230 C, held for 30 min; ion source temperature, 280 C; injector temperature,250 C; split ratio, 1:20; carrier gas, helium; ow rate, 0.7 mL/min.

    2.4. Identication and quantication

    Retention indices of all the constituents were determined on both phases byKovats method using n-alkanes as standards. Constituents of the volatile oil were

    Table 1

    Plant material, collection places, dates, life-cycle stages and oil yields of Psiadia species

    Species Voucher

    number

    Part Collection places

    (altitudes)

    Date Life-cycle

    stages

    Oil

    yield (%)

    P. anchusifolia DIV18 Leaves Reunion Island:

    volcano area

    (2300 m)

    April 2000 Vegetative 0.089

    November 2001 Flowering 0.088

    P. argentea DIV19 Aerial

    parts

    Reunion Island:

    volcano area

    (2300 m)

    April 2000 Vegetative 0.020

    November 2001 Flowering 0.015

    P. boivinii DIV17 Leaves Reunion Island:

    forest of

    Belouve-Bebour

    (1500 m)

    April 2000 Vegetative 0.002

    November 2001 Flowering 0.008

    P. salaziana DIV16 Leaves Reunion Island:

    volcano area

    (2300 m)

    April 2000 Vegetative 0.120

    November 2001 Flowering 0.065

    707A. Gauvin, J. Smadja / Biochemical Systematics and Ecology 33 (2005) 705e714

  • identied by comparison of their retention indices and their massspectral fragmentation pattern with those reported in the literature (Adams,2001) and stored on MS Library (NBS75K). The quantication of the com-ponents was performed on the basis of their GC peak areas on the Supelcowaxcolumn.

    3. Results and discussion

    The taxonomy of the genus Psiadia is rather complex. Thus, in the Mascarenes,the taxonomic scheme established by Scott (1991) is built on the segregation of thegenus into ve groups mostly based on morphological characters. The four taxainvestigated here are endemic to Reunion Island and belong to two dierentgroups.

    P. anchusifolia and P. boivinii belong to the group of shrubs or small trees, denselyhairy; the hairs are often brownish. The inorescences are much branched, bearinglarger heads containing numerous orets; the phyllaries are lanceolated and rathersti; the female orests are sparsely hispid with very short ray; the achenes arecompressed.

    P. argentea and P. salaziana belong to the group of subshrubs. The leavesare small, sessile and often densely hairy; the heads are large and subspherical,solitary or in groups of three; the phyllaries are generally herbaceous andlanceolated; the female orest possesses a short or no ray; the achenes arecompressed.

    The essential oils of these four species of Psiadia were obtained by hydro-distillation during the vegetative (April) and owering (November) phases. The oilyields are reported in Table 1 and were found to be low especially for P. boivinii.Moreover, the yields were about the same in April and November, except forP. salaziana which gave a slightly higher percentage of essential oil during thevegetative phase.

    The identied volatile components are listed according to their chemicalstructures in Table 2. The table also includes their retention indices and the per-centage composition. Altogether, 57 compounds were identied amounting to58.5e82.9% of the total oils.

    For P. anchusifolia, P. argentea and P. salaziana, the qualitative and quantitativecomposition of the oils appeared to be not dependent on the stage of plantdevelopment. Moreover, the oils of these three species were characterized by a largepresence of terpenoids mainly oxygenated mono- (12.8e45.8%) and sesquiterpenes(28.4e39.3%). The main similarities in their composition are also related to the highpercentages of the two unusual components: compound 1 (12.0e41.4%) among theoxygenated monoterpene fraction, compound 2 (19.2e39.3%) among the oxygen-ated sesquiterpene fraction. These two major components were detected and isolatedfor the rst time from P. anchusifolia (Gauvin et al., 2004) and were identied as

    708 A. Gauvin, J. Smadja / Biochemical Systematics and Ecology 33 (2005) 705e714

  • 7,7-dimethyl-2-methylenebicyclo[3.3.1]heptan-6-ol acetate for 1 and 6,6,8,9-tetrame-thyltricyclo[3.3.3.0]-undec-7-en-2-ol for 2. This is the second report on theoccurrence of these rare terpenoids in nature.

    In contrast, the essential oils of P. boivinii showed a dierent composition patterndepending on the stage of plant development. During the vegetative stage, theessential oil was dominated by oxygenated sesquiterpenes (28.8%) and sesquiterpenehydrocarbons (14.4%). The rest being mainly oxygenated monoterpenes (10.9%).Like P. anchusifolia, P. argentea and P. salaziana, the two major constituents of thisoil were the oxygenated sesquiterpene 2 (19.6%) and the oxygenated monoterpene 1(5.2%). The chemical composition of the essential oil of P. boivinii collected duringowering, was quite distinguishable. The oil was characterized by a great prevalenceof mono- (29.8%) and sesquiterpene (24.5%) hydrocarbons, b-pinene (10.6%),(E )-b-ocimene (10.0%), germacrene D (8.5%) and b-elemene (5.6%) being the maincomponents. It is worth mentioning that the oil was not completely devoid ofterpenoids 1 and 2 as they were detected in low concentrations (4.9 and 2.0%,respectively).

    The occurrence of the unusual terpenoids 1 and 2 in P. anchusifolia, P. argentea,P. boivinii and P. salaziana supposes that the four species have the same biosynthe-tic pathway and it may also suggest that both 1 and 2 could be used asa chemotaxonomic tool for the characterization of some Psiadia species. However,chemical variations related to environmental conditions are frequently encounteredin aromatic plants. Further investigations are therefore needed to prove that theoccurrence of terpenoids 1 and 2 in the four species depends more on the geneticsimilarities between the plants than the environmental conditions. To complete thischemotaxonomic study, it would also be interesting to nd other species of Psiadiawith compounds 1 and 2 in their essential oil composition.

    O

    O

    OH

    1 2

    709A. Gauvin, J. Smadja / Biochemical Systematics and Ecology 33 (2005) 705e714

  • P. boivinii P. salaziana

    April November April November

    0.5 0.2 e e

    3.0 0.4 t t

    0.5 e e e4.0 0.6 t t

    e e e e

    e e e ee e e e

    e e e e

    e 1.2 e e

    e 10.6 0.5 1.1

    e 1.7 3.6 5.2e e e e

    t 4.8 0.4 0.3

    e e t te 0.5 t t

    e 10.0 0.5 0.7

    t 1.0 t t

    t 29.8 5.0 7.3

    1.2 t e e

    1.0 t e e

    3.2 1.0 t t

    0.3 e 1.5 1.3

    5.2 4.9 21.2 18.6

    710

    A.Gauvin

    ,J.Smadja/Biochem

    icalSystem

    atics

    andEcology33(2005)705e

    714Table 2

    Volatile constituents identied in the essential oils of Psiadia species from Reunion Island

    Compounds RIa %b

    Supelcowax HP-5MS P. anchusifolia P. argentea

    April November April November

    Hydrocarbons

    Alcohols

    n-Hexanol 1311 e e e e e

    3-Hexen-1-ol 1345 e 0.4 1.2 e e

    2-Hexen-1-ol 1364 e e e e eTotal 0.4 1.2 e e

    Aldehydes

    Hexenal 1061 e e e 0.7 e

    n-Octanal 1266 e e e t en-Nonanal 1366 1095 e e 1.3 0.7

    Total e e 2.0 0.7

    Terpenoids

    Monoterpene hydrocarbons

    a-Pinene 1016 e e e e e

    b-Pinene 1092 970 0.2 0.2 e 0.3

    Myrcene 1136 987 0.3 t e 0.9a-Phellandrene 1148 e t e e e

    Limonene 1184 1024 t t e t

    b-Phellandrene 1196 1024 t t e e(Z )-b-ocimene 1211 1032 0.2 e e e

    (E )-b-ocimene 1228 1042 1.8 t e e

    p-Cymene 1251 1023 t t e t

    Total 2.5 0.2 e 1.2Oxygenated monoterpenes

    cis-Linalool oxide 1410 1065 e e t t

    trans-Linalool oxide 1438 1080 e e t e

    Linalool 1500 1091 t t 0.3 0.3

    cis-Chrysanthenyl acetate 1540 1256 0.8 0.8 2.3 4.1

    1 1646 1313 12.0 14.1 18.2 41.4

  • e e e e

    t e e e

    10.9 5.9 22.7 19.9

    0.7 0.5 1.2 1.0

    2.9 1.8 1.4 1.5

    e 1.5 0.5 0.40.6 m 0.5 0.4

    e e e e

    3.4 5.6 1.1 0.7

    0.5 0.6 2.3 1.9

    e 1.0 1.5 1.0

    e e 1.8 1.3

    2.1 0.5 e e

    e e 0.6 1.1e 8.5 3.1 2.6

    0.6 1.1 0.5 0.8

    1.4 0.3 e em 0.4 0.3 0.4

    t 2.2 0.5 1.6

    1.3 0.2 t 0.4

    0.5 0.3 t 0.4

    0.4 t e e

    t t e e

    14.4 24.5 15.3 15.5

    e 0.6 1.2 0.6

    e 0.6 3.8 2.4

    e e 0.8 0.60.4 e t t

    0.7 0.3 0.6 m

    e e 0.7 m

    19.6 2.0 26.6 28.5

    1.9 1.0 1.3 1.1

    (continued on next page)

    711

    A.Gauvin

    ,J.Smadja/Biochem

    icalSystem

    atics

    andEcology33(2005)705e

    714trans-Myrtanol acetate 1719 1375 e e t t

    Cuminaldehyde 1762 1237 e e e e

    Total 12.8 14.9 20.8 45.8

    Sesquiterpene hydrocarbons

    a-Copaene 1483 1368 t 0.6 t t

    b-Maalienec 1515 1372 0.9 1.5 1.0 0.5

    b-Cubebene 1518 1382 t 0.2 e ea-Isocomene 1525 1378 t 0.4 t t

    a-trans-Bergamotene 1564 1429 t t e e

    b-Elemene 1569 1386 0.9 1.2 1.0 1.0

    b-Copaenec 1580 1422 t m t t

    b-Caryophyllene 1583 e 0.6 m e e

    a-Humulene 1655 1444 0.9 1.0 e e

    g-Muurolene 1668 1466 e e t e

    d-Selinene 1671 1483 2.7 2.7 e eGermacrene D 1695 1476 4.0 3.3 e e

    a-Muurolene 1703 1491 0.3 0.6 e e

    b-Selinene 1706 1476 e e t ta-Selinene 1711 1487 0.5 1.0 e e

    d-Cadinene 1733 1514 0.5 1.0 t e

    g-Cadinene 1739 1505 e e t e

    trans-Calamene 1807 1512 e e m ta-Calacorene 1890 1533 e e m t

    b-Calacorene 1931 1554 e e t t

    Total 11.3 13.5 2.0 1.5

    Oxygenated sesquiterpenes

    Epicubebol 1854 1487 0.7 0.8 t e

    Cubebol 1903 1510 2.4 1.7 e e

    Caryophyllene oxide 1964 1583 e e 2.3 0.7Nerolidold 1977 e 0.6 0.2 e e

    Humulene epoxide II 2018 1601 e e 1.0 0.3

    Elemol 2031 1549 2.6 1.4 t 0.2

    2 2109 1580 20.5 19.2 39.3 28.3

    T-muurolol 2147 1635 0.7 0.6 m 0.3

  • Table 2 (continued)

    folia P. argentea P. boivinii P. salaziana

    November April November April November April November

    6.3 e e e e 1.6 2.8

    5.6 e e 0.6 e 1.2 2.40.6 0.6 0.7 2.7 1.4 1.2 1.3

    1.6 e e 0.8 - 0.7 0.5

    0.6 e e 1.7 0.4 t t

    38.6 43.2 30.5 28.4 6.3 39.7 40.2

    e e e 0.4 0.4 e e

    e t t e e e ee t t 0.4 0.4 e e

    68.4 68.0 79.7 58.1 67.5 82.7 82.9

    x capillary column and on the HP-5MS column.

    column; m: mixture; t: trace (!0.1%).

    712

    A.Gauvin

    ,J.Smadja/Biochem

    icalSystem

    atics

    andEcology33(2005)705e

    714Compounds RIa %b

    Supelcowax HP-5MS P. anchusi

    April

    Bulnesol 2171 1665 7.0

    a-Eudesmol 2188 1649 4.6

    a-Cadinol 2191 1650 0.9

    b-Eudesmol 2196 e 1.2

    Selin-11-en-4-a-ol 2217 e 0.6

    Total 41.8

    Miscellaneous compounds

    (E )-b-damascone 1786 1406 e

    b-Ionone 1907 1478 eTotal e

    % Identication 68.8

    a Retention indices relative to C8eC22 n-alkanes on the Supelcowab Relative percentage obtained from peak area on the Supelcowaxc Tentatively identied.d Correct isomer non-identied.

  • Acknowledgements

    Financial support from the Conseil Regional of Reunion Island is gratefullyacknowledged.

    References

    Abou-Zaid, M.M., El-Karemy, Z., El-Negoumy, S.I., Altosaar, I., Saleh, N.A.M., 1991. The avonoids of

    Psiadia punctulata. Bull. Chem. Soc. Ethiop. 5, 37e40.

    Adams, R.P., 2001. Identication of Essential Oils by Gas Chromatography/Quadrupole Mass

    Spectroscopy. Allured Publishing Corporation, Carol Stream, Illinois, USA.

    Al-Yahya, M.A., Hifnawy, M.S., Mossa, J.S., El-Feraly, F.S., McPhail, D.R., McPhail, A.T., 1987. X-ray

    structure of psiadiarabin, a avone from Psiadia arabica. Phytochemistry 26, 2648e2649.

    Bosser, J., Gueho, J., Jerey, C., 1993. In: Antoine, R., Bosser, J., Ferguson, I.K. (Eds.), Flore des

    Mascareignes. La Reunion, Maurice, Rodrigues, 109. Composees. ORSTOM, Paris, pp. 80e103.Canonica, L., Rindone, B., Scolastico, C., Ferrari, G., Casagrande, C., 1967. Structure and

    stereochemistry of psiadiol, a new diterpenoid. Tetrahedron Lett. 28, 2639e2643.

    Canonica, L., Rindone, B., Scolastico, C., Ferrari, G., Casagrande, C., 1969a. Gazz. Chim. Ital. 99, 260.

    Canonica, L., Rindone, B., Scolastico, C., Ferrari, G., Casagrande, C., 1969b. Gazz. Chim. Ital. 99, 276.

    Dennis, R., 1973. Essential oil of Psiadia salviifolia. Phytochemistry 12, 2705e2708.

    El-Domiaty, M.M., El-Feraly, F.S., Mossa, J.S., McPhail, A.T., 1993. Diterpenes from Psiadia arabica.

    Phytochemistry 34, 467e471.El-Feraly, F.S., Mossa, J.S., Al-Yahya, M.A., Hifnawy, M.S., Hafez, M.M., Huord, C.D., 1990. Two

    avones from Psiadia arabica. Phytochemistry 29, 3372e3373.

    Fortin, H., Tomasi, S., Jaccard, P., Robin, V., Boustie, J., 2001. A prenyloxycoumarin from Psiadia

    dentata. Chem. Pharm. Bull. 49, 619e621.Gauvin, A., Susperregui, A., Barth, P., Remy, L., Deleris, G., Smadja, J., 2004. An acetylated

    monoterpene and a sesquiterpene alcohol from Psiadia anchusifolia. Phytochemistry 65, 897e901.

    Gurib-Fakim, A., Bourrel, C., Kodja, H., Govinden, J., 1995. Chemical composition of the essential oils

    of Psiadia lithospermifolia (Lam.) Cordem. and P. viscosa (Lam.) A.J. Scott of the Asteraceae family.

    J. Essent. Oil Res. 7, 533e535.

    Gurib-Fakim, A., Gauvin, A., Smadja, J., Govinden-Soulange, J., Kodja, H., 2000. Composition of the

    essential oil of the endemic Psiadia arguta Pers. (Voigt) from Mauritius. J. Essent. Oil Res. 12, 556e558.

    Jakobsen, T.H., Marcussen, H.V., Adsersen, A., Strasberg, D., Smitt, U.W., Jaroszewski, J.W., 2001.

    3-Methoxyavones and a novel coumarin from Psiadia dentata. Biochem. Syst. Ecol. 29, 963e965.

    Juma, B.F., Yenesew, A., Midiwo, J.O., Waterman, P.G., 2001. Flavones and phenylpropenoids in the

    surface exudate of Psiadia punctulata. Phytochemistry 57, 571e574.

    Mekkawi, A.G., Mossa, J.S., Hifnawy, M.S., Karawya, M.S., 1984. Essential oil of Psiadia arabica Jaub.

    et Spach. Pharmazie 39, 419e420.

    Midiwo, J.O., Owuor, F.A.O., Juma, B.F., Waterman, P.G., 1997. Diterpenes from the leaf exudate of

    Psiadia punctulata. Phytochemistry 45, 117e120.

    Mossa, J.S., Mekkawi, A.G., Hifnawy, M.S., Karawya, M.S., 1983. Essential oil of Psiadia arabica Jaub.

    Et. sp. In: IX International Congress of Essentials Oils. Essential Oil Technical Paper, Book 4,

    Singapore pp. 45e47.

    Mossa, J.S., El-Domiaty, M.M., Al-Meshal, I.A., El-Feraly, F.S., Huord, C.D., McPhail, D.R.,

    McPhail, A.T., 1992. A avone and diterpene from Psiadia arabica. Phytochemistry 31, 2863e2868.

    Ramanoelina, P.A.R., Rasoarahona, J.R.E., Masotti, V., Viano, J., Gaydou, E.M., Bianchini, J.P., 1994.

    Chemical composition of the leaf oil of Psiadia altissima (Compositeae). J. Essent. Oil Res. 6, 565e570.

    Robin, V., Boustie, J., Amoros, M., Girre, L., 1998. In-vitro antiviral activity of seven Psiadia species,

    Asteraceae: isolation of two antipoliovirus avonoids from Psiadia dentata. Pharm. Pharmacol.

    713A. Gauvin, J. Smadja / Biochemical Systematics and Ecology 33 (2005) 705e714Commun. 4, 61e64.

  • Scott, A.J., 1991. Notes on Compositae-Astereae for the Flore des Mascareignes. Kew Bull. 2, 339e353.

    Wang, Y., Hamburger, M., Gueho, J., Hostettmann, K., 1989a. Antimicrobial avonoids from Psiadia

    trinervia and their methylated and acetylated derivatives. Phytochemistry 28, 2323e2327.Wang, Y., Hamburger, M., Hostettmann, K., 1989b. Antifungal methylated avonols from Psiadia

    trinervia. Planta Med. 55, 109.

    Wang, Y., Hamburger, M., Gueho, J., Hostettmann, K., 1992. Cyclohexanecarboxylic-acid derivatives

    from Psiadia trinervia. Helv. Chim. Acta 75, 269e275.

    714 A. Gauvin, J. Smadja / Biochemical Systematics and Ecology 33 (2005) 705e714

    Essential oil composition of four Psiadia species from Reunion Island: A chemotaxonomic studyIntroductionMaterial and methodsPlant materialSampling and essential oil extractionGas chromatography-mass spectrometry analysesIdentification and quantification

    Results and discussionAcknowledgementsReferences

Recommended

View more >