Research Article
Ambika Poudel
Ambika Poudel
Aromatic Plant
Research Center, 230 N 1200 E, Suite 100, Lehi, UT 84043, USA
Prabodh Satyal
Prabodh Satyal
Aromatic Plant
Research Center, 230 N 1200 E, Suite 100, Lehi, UT 84043, USA
Kathy Swor
Kathy Swor
Independent Researcher, 1432 W.
Heartland Dr, Kuna, ID 83634, USA
William N. Setzer
William N. Setzer
Corresponding Author
Aromatic Plant Research Center, 230 N 1200 E, Suite 100, Lehi, UT
84043, USA
And
Department of Chemistry, University of Alabama in Huntsville,
Huntsville, AL 35899, USA
E-mail: wsetzer@chemistry.uah.edu; Tel.: +1-256-468-2862
Abstract
Chaenactis
douglasii and Dieteria canescens are two members of
the Asteraceae found in western North America and utilized by Native Americans
as herbal medicines. The purpose of this investigation was to examine
previously unstudied/understudied volatile phytochemistry of members of the
Asteraceae from southwestern Idaho as well as to extend our understanding of
the properties of Native American aromatic medicinal plants. The essential oils
from the fresh aerial parts were obtained by hydrodistillation and analyzed by
gas chromatographic methods. The colorless essential oil of C. douglasii
was obtained in 0.024% yield, while D. canescens gave a pale-yellow
essential oil in 0.418% yield. Tiglic acid (35.9%) dominated the essential oil
of C. douglasii, followed by thymol (8.4%), δ-cadinene
(5.0%), and 8α-acetoxyelemol (4.7%). There was also a large
concentration of an unidentified component (RI = 1998, 8.7%). The major
components in D. canescens essential oil were δ-cadinene
(28.3%), epi-cubebol (24.4%), 1-epi-cubenol (10.9%), and cubenol
(7.7%). (–)-β-Pinene, (–)-germacrene D, (+)-δ-cadinene, and (+)-(E)-nerolidol
were the exclusive enantiomers found in C. douglasii essential oil,
while (+)-α-pinene (75.7%) was the major enantiomer for α-pinene. In D.
canescens essential oil, the (–)-enantiomers were predominant for α- and
β-pinene (90.3% and 90.4%, respectively), cis- and trans-sabinene
hydrate (86.9% and 85.0%, respectively), terpinen-4-ol (66.8%), α-terpineol
(64.8%), and germacrene D (100%), while the (+)-enantiomer was the major for
limonene (95.8%) and δ-cadinene (100%). A perusal of the literature reveals there
to be no obvious trends in enantiomeric distributions of terpenoids in the
Asteraceae.
Abstract Keywords
Douglas’
dustymaiden, hoary tansyaster, Asteraceae, enantiomeric distribution, gas chromatography,
chiral
1. Introduction
Numerous members of the Asteraceae growing in desert regions of western North America have been used as traditional herbal medicines by Native American tribes [1]. Two members of the family, Chaenactis douglasii (Hook.) Hook. & Arn (Douglas’ dustymaiden) and Dieteria canescens (Pursch) Nutt. (syn. Machaeranthera canescens (Pursch) A. Gray, hoary tansyaster) have been understudied in terms of their volatile phytochemicals.
Chaenactis douglasii occurs in western North America from British Columbia, south to southern California, northern Arizona and northern New Mexico, and east into Montana, Wyoming, and Colorado [2, 3]. Several Native North American tribes used C. douglasii as traditional medicines. For example, the Paiute took a decoction of the plant to treat coughs and colds, the Shoshoni used a poultice of crushed plants to treat swellings, and the Thompson people used a decoction of the plant on skin conditions and insect bites [1]. Guaianolide and germacranolide sesquiterpene lactones have been isolated and identified in the aerial parts of C. douglasii [4–6]. The crude methanol extract (not phytochemically characterized) of C. douglasii from British Columbia, Canada, was screened for antibacterial [7] and antifungal [8] activity. The extract showed activity against Bacillus subtilis, Escherichia coli, Mycobacter phlei, both methicillin-susceptible and methicillin-resistant Staphylococcus aureus, Salmonella typhimurium, Microsporum cookerii, Microsporum gypseum, and Trichophyton mentagrophytes. Apparently there have been no previous reports on the essential oil composition of C. douglasii, however.
Dieteria canescens ranges throughout western North America from Canada, south through California, Arizona, and New Mexico, to Mexico [3, 9]. The Navajo used the dried, pulverized plant material as a snuff to treat throat problems, while a decoction of the plant was taken by parturient Hopi women for any disorder [1]. As far as we are aware, there are no previous studies on the phytochemistry of D. canescens.
Both C. douglasii and D. canescens are important native members of the plant communities of the Great Basin [10]. However, these native plant communities of the Great Basin are being lost or degraded at an alarming rate due to overgrazing, wildfires, drought, and invasive species; the sagebrush steppe is one of the most endangered ecosystems of North America [11,12]. Although relatively understudied, C. douglasii [13] and D. canescens [14] have been highlighted as priority species for restoration of degraded habitats in the Great Basin. However, neither plant has been investigated in terms of essential oil composition. As part of our continuing interest in essential oils of aromatic/medicinal plants of the Great Basin, the purpose of this study was to investigate the essential oil compositions of these two members of the Asteraceae, C. douglasii and D. canescens collected from Boise, Idaho.
2. Materials and methods
2.1 Plant
material
Aerial parts of C. douglasii and D. canescens were collected from the Idaho Botanical Garden (43°36ʹ04″N, 116°09ʹ35″W, 862 m elevation) on 29 July 2021. The plants were identified by Daniel Murphy, Collections Curator, Idaho Botanical Garden. The fresh aerial parts of C. douglasii (17.34 g) were hydrodistilled using a Likens-Nickerson apparatus with continuous extraction with dichloromethane for 3 h to give a colorless residue (4.1 mg). The fresh aerial parts of D. canescens (48.19 g) were hydrodistilled for 3 h to give a pale-yellow essential oil (201.2 mg).
2.2 Gas
chromatographic analyses
The
aerial parts essential oils of C. douglasii and D. canescens were
analyzed by GC-MS as previously reported [15]:
Shimadzu GCMS-QP2010 Ultra (Shimadzu Scientific Instruments, Columbia, MD,
USA), ZB-5ms capillary column (60 m × 0.25 mm, 0.25 μm film thickness,
Phenomenex, Torrance, CA, USA); He carrier gas, head pressure = 208.3 kPa, flow
rate = 2.00 mL/min, injector temperature = 260 °C, ion source temperature = 260
°C, interface temperature = 260 °C, GC oven program (50 °C initial temperature,
ramp up to 260 °C at 2 °C/min, held at 260 °C for 5 min); 0.1 μL injection, 5%
w/v essential oil/CH2Cl2, 24.5:1 split mode. A series of
homologous n-alkanes was used to calculate the retention indices (RI) [16]. Chemical components were identified by
comparing MS fragmentation and RI values with those in the Adams [17],
FFNSC3 [18],
NIST20 [19], and Satyal [20] databases. Gas chromatography – flame ionization detection
(GC-FID) was carried out as previously described [15]:
Shimadzu GC 2010 with FID detector (Shimadzu Scientific Instruments, Columbia,
MD, USA), ZB-5 capillary column (60 m ´
0.25 mm ´ 0.25 μm film
thickness) (Phenomenex, Torrance, CA, USA), same operating conditions as above
for GC-MS. The percent compositions were determined from raw peak areas without
standardization. Chiral GC-MS was used to evaluate the enantiomeric
distributions of chiral terpenoids as previously reported [15]:
Shimadzu GCMS-QP2010S (Shimadzu Scientific Instruments, Columbia, MD, USA),
Restek B-Dex 325 column (30 m ´
0.25 mm diameter ´
0.25 μm film thickness) (Restek Corp., Bellefonte, PA, USA); He carrier gas,
head pressure = 53.6 kPa, flow rate = 1.00 mL/min, injector and detector
temperatures = 240 °C, GC oven program (50 °C initial temperature held for 5
min, ramp up to 100 °C at 1.0 °C/min, then ramp to 220 °C at 2.0 °C/min); 0.3
μL injection, 5% w/v essential oil/CH2Cl2, 24.0:1 split
mode. Retention indices (RI) determined with respect to a series (C8-C21)
of n-alkanes. Enantiomers were determined by comparison of RI values
with those in our in-house database. The enantiomer percentages were determined
from raw peak areas.
3. Results and
discussion
Hydrodistillation
of the aerial parts of C. douglasii gave a colorless essential oil in very
low (0.024%) yield while the aerial parts of D. canescens gave a
pale-yellow essential oil in 0.418% yield. Gas chromatographic analyses (GC-MS and
GC-FID) of the two essential oils are summarized in Table 1.
Table 1. Chemical composition (%) of the aerial parts essential oil of Chaenactis douglasii and Dieteria canescens.
RIcalc |
RIdb |
Compound |
C. douglasii |
D. canescens |
933 |
933 |
α-Pinene |
0.2 |
0.4 |
941 |
942 |
Tiglic
acid |
35.9 |
- |
949 |
950 |
Camphene |
- |
0.1 |
971 |
971 |
Sabinene |
- |
tr |
978 |
978 |
β-Pinene |
1.6 |
1.3 |
979 |
979 |
Caproic
acid |
0.7 |
- |
988 |
989 |
Myrcene |
- |
0.3 |
1007 |
1007 |
α-Phellandrene |
- |
tr |
1017 |
1018 |
α-Terpinene |
- |
tr |
1024 |
1024 |
p-Cymene |
- |
0.5 |
1026 |
1026 |
2-Acetyl-3-methylfuran |
- |
tr |
1029 |
1030 |
Limonene |
- |
0.5 |
1030 |
1031 |
β-Phellandrene |
- |
tr |
1031 |
1032 |
1,8-Cineole |
- |
tr |
1035 |
1035 |
(Z)-β-Ocimene |
- |
tr |
1045 |
1045 |
(E)-β-Ocimene |
- |
tr |
1057 |
1057 |
γ-Terpinene |
- |
tr |
1069 |
1069 |
cis-Sabinene
hydrate |
- |
0.2 |
1085 |
1086 |
Terpinolene |
- |
tr |
1100 |
1101 |
trans-Sabinene
hydrate |
- |
0.1 |
1107 |
1106 |
α-Pinene
oxide |
- |
tr |
1121 |
1121 |
trans-p-Mentha-2,8-dien-1-ol |
- |
tr |
1124 |
1126 |
cis-p-Menth-2-en-1-ol |
- |
0.1 |
1137 |
1137 |
Nopinone |
- |
tr |
1141 |
1142 |
trans-p-Menth-2-en-1-ol |
- |
0.1 |
1145 |
1145 |
trans-Verbenol |
- |
0.2 |
1149 |
1146 |
trans-Limonene
oxide |
- |
tr |
1161 |
1164 |
Pinocarvone |
- |
tr |
1171 |
1170 |
Borneol |
- |
tr |
1175 |
1176 |
cis-Pinocamphone |
- |
tr |
1180 |
1180 |
Terpinen-4-ol |
- |
1.2 |
1186 |
1186 |
p-Cymen-8-ol |
- |
0.1 |
1195 |
1195 |
α-Terpineol |
0.3 |
0.1 |
1196 |
1196 |
cis-Piperitol |
- |
tr |
1206 |
1206 |
Verbenone |
- |
tr |
1208 |
1208 |
trans-Piperitol |
- |
tr |
1283 |
1282 |
Bornyl
acetate |
0.5 |
0.1 |
1289 |
1289 |
Thymol |
8.4 |
- |
1348 |
1348 |
α-Cubebene |
- |
0.7 |
1376 |
1375 |
α-Copaene |
- |
0.4 |
1384 |
1382 |
β-Bourbonene |
- |
0.1 |
1387 |
1385 |
α-Isocomene |
0.2 |
- |
1390 |
1392 |
β-Cubebene |
- |
0.9 |
1407 |
1406 |
α-Gurjunene |
- |
0.1 |
1418 |
1422 |
β-Ylangene |
- |
tr |
1419 |
1417 |
(E)-β-Caryophyllene |
- |
0.1 |
1446 |
1447 |
Geranyl
acetone |
0.3 |
- |
1449 |
1448 |
cis-Muurola-3,5-diene |
- |
0.1 |
1454 |
1454 |
α-Humulene |
0.2 |
tr |
1465 |
1464 |
Ylangol |
- |
tr |
1469 |
1463 |
cis-Cadina-1(6),4-diene |
- |
tr |
1472 |
1472 |
trans-Cadina-1(6),4-diene |
- |
0.6 |
1475 |
1475 |
γ-Muurolene |
- |
0.1 |
1476 |
1481 |
(E)-β-Ionone |
0.1 |
- |
1482 |
1483 |
Germacrene
D |
0.7 |
0.2 |
1489 |
1489 |
β-Selinene |
- |
0.1 |
1492 |
1492 |
trans-Muurola-4(14),5-diene |
0.7 |
1.9 |
1496 |
1497 |
epi-Cubebol |
2.3 |
24.4 |
1497 |
1497 |
α-Muurolene |
0.3 |
- |
1511 |
1510 |
Tridecanal |
0.5 |
- |
1516 |
1515 |
Cubebol |
0.9 |
2.9 |
1518 |
1518 |
δ-Cadinene |
5.0 |
28.3 |
1520 |
1519 |
trans-Calamenene |
0.6 |
- |
1522 |
1521 |
Zonarene |
0.3 |
- |
1523 |
1524 |
Dihydroactinidiolide |
0.3 |
- |
1526 |
1527 |
trans-Calamenene |
- |
3.8 |
1533 |
1533 |
trans-Cadine-1,4-diene |
0.4 |
0.6 |
1542 |
1541 |
α-Calacorene |
- |
0.4 |
1549 |
1549 |
α-Elemol |
2.9 |
0.3 |
1560 |
1561 |
(E)-Nerolidol |
0.3 |
- |
1562 |
1564 |
β-Calacorene |
- |
0.3 |
1570 |
1568 |
Palustrol |
- |
0.2 |
1575 |
1576 |
Spathulenol |
0.4 |
- |
1584 |
1590 |
Globulol |
0.3 |
- |
1588 |
1590 |
Gleenol |
- |
1.4 |
1590 |
- |
Unidentifieda |
- |
1.8 |
1592 |
- |
Unidentifiedb |
- |
2.7 |
1593 |
1594 |
Viridiflorol |
0.2 |
- |
1600 |
1600 |
Hexadecane |
0.2 |
- |
1613 |
1613 |
Tetradecanal |
0.2 |
- |
1622 |
1624 |
Selina-6-en-4β-ol |
0.9 |
- |
1629 |
1628 |
1-epi-Cubenol |
3.2 |
10.0 |
1631 |
1632 |
γ-Eudesmol |
0.9 |
0.1 |
1643 |
1643 |
Cubenol |
2.3 |
7.7 |
1643 |
1644 |
τ-Muurolol |
0.9 |
- |
1646 |
1644 |
α-Muurolol
(= δ-Cadinol) |
0.7 |
1.9 |
1654 |
1655 |
α-Cadinol |
3.8 |
- |
1657 |
1663 |
cis-Calamenen-10-ol |
- |
0.5 |
1663 |
1665 |
Intermedeol |
1.8 |
- |
1664 |
1662 |
9-Methoxycalamenene |
- |
0.4 |
1714 |
1715 |
Pentadecanal |
0.4 |
- |
1757 |
1758 |
Myristic
acid |
0.3 |
- |
1777 |
1775 |
8α-Acetoxyelemol |
4.7 |
0.2 |
1792 |
1793 |
α-Phellandrene
dimer A |
0.5 |
- |
1840 |
1841 |
Phytone |
0.2 |
- |
1889 |
1891 |
(E)-Hexadecantrienal |
0.7 |
- |
1957 |
1958 |
Palmitic
acid |
0.3 |
- |
1998 |
- |
Unidentifiedc |
8.7 |
- |
|
|
Total identified |
86.4 |
93.9 |
Compound Classes |
||||
Monoterpene hydrocarbons |
1.8 |
3.0 |
||
Oxygenated monoterpenoids |
9.1 |
2.2 |
||
Sesquiterpene hydrocarbons |
8.4 |
38.7 |
||
Oxygenated sesquiterpenoids |
26.7 |
49.9 |
||
Diterpenoids |
0.5 |
0.0 |
||
Others |
39.9 |
traces |
RIcalc
= Retention index calculated with respect to a homologous series of n-alkanes
on a ZB-5ms column. RIdb = Reference retention index values from the
databases [17–20]. tr = trace (<
0.05%), - = not detected. a MS(EI): 222(3%), 208(13%), 207(90%),
204(17%), 161(57%), 137(18%), 135(21%), 123(25%), 119(22%), 105(38%), 95(26%),
91(18%), 55(17%), 43(100%), 41(24%). b MS(EI): 222(2%), 208(14%),
207(100%), 179(9%), 161(37%), 135(19%), 123(23%), 119(22%), 105(35%), 95(26%),
91(21%), 81(27%), 55(18%), 43(88%), 41(26%). c MS(EI): 230(13%),
215(8%), 186(8%), 169(8%), 157(11%), 145(84%), 143(22%), 129(23%), 117(23%),
105(30%), 194(100%), 91(59%), 79(44%), 77(35%), 65(17%), 53(14%), 41(24%).
Tiglic acid (35.9%) dominated the
essential oil of C. douglasii, followed by thymol (8.4%), δ-cadinene (5.0%), and 8α-acetoxyelemol (4.7%). There was also a
large concentration of an unidentified component (RI = 1998, 8.7%). Although
the essential oil yield and the terpenoid content were low, the enantiomeric
distributions for the monoterpenoids α-pinene,
β-pinene, and α-terpineol, as well as the
sesquiterpenoids germacrene D, δ-cadinol,
and (E)-nerolidol, were determined (Table 2). (+)-α-Pinene was the predominant enantiomer
(enantiomeric excess, %ee, = 51.4%) and α-terpineol
was nearly racemic [52.4% (+), 47.6% (–)]; the (–) enantiomers were found exclusively for
β-pinene and
germacrene D, while the (+)-enantiomers were observed for δ-cadinene, and (E)-nerolidol.
The
major components in D. canescens essential oil were δ-cadinene
(28.3%), epi-cubebol (24.4%), 1-epi-cubenol (10.9%), and cubenol
(7.7%). The levorotatory enantiomers were dominant for the monoterpenes α-pinene
(ee 80.6%), β-pinene (ee 80.8%), camphene (ee 84.2%),
cis-sabinene hydrate (ee 73.8%) trans-sabinene hydrate (ee 70.0%),
terpinen-4-ol (ee 33.6%), and α-terpineol (ee 29.6%).
On the other hand, (+)-limonene was the major limonene enantiomer (ee 91.6%). As
observed in C. douglasii, the (–) enantiomer was the
exclusive stereoisomer for the germacrene D, while (+)-δ-cadinene
was the only enantiomer observed in D. canescens.
Table 2. Enantiomeric distributions of chiral terpenoids detected in Chaenactis douglasii
and Dieteria canescens essential oils.
Compound |
Database |
C. douglasii EO |
D. canescens EO |
||
RT (RI) |
RT (RI) |
ED (%) |
RT (RI) |
ED (%) |
|
(–)-α-Pinene |
15.92
(976) |
16.34
(976) |
24.3 |
16.36
(976) |
90.3 |
(+)-α-Pinene |
16.40
(982) |
16.78
(981) |
75.7 |
16.86
(983) |
9.7 |
(+)-β-Pinene |
20.27
(1027) |
- |
0.0 |
20.80
(1027) |
9.6 |
(–)-β-Pinene |
20.62
(1030) |
21.36
(1032) |
100.0 |
21.22
(1031) |
90.4 |
(–)-Limonene |
25.06
(1073) |
- |
- |
25.73
(1074) |
4.2 |
(+)-Limonene |
25.99
(1081) |
- |
- |
26.47
(1080) |
95.8 |
(+)-cis-Sabinene hydrate |
40.70
(1199) |
- |
- |
41.48
(1198) |
13.1 |
(–)-cis-Sabinene hydrate |
41.25
(1202) |
- |
- |
41.98
(1200) |
86.9 |
(+)-trans-Sabinene
hydrate |
46.15
(1230) |
- |
- |
46.96
(1231) |
15.0 |
(–)-trans-Sabinene
hydrate |
46.84
(1235) |
- |
- |
47.63
(1235) |
85.0 |
(+)-Terpinen-4-ol |
54.64
(1297) |
- |
- |
55.40
(1299) |
33.2 |
(–)-Terpinen-4-ol |
54.93
(1299) |
- |
- |
55.70
(1302) |
66.8 |
(–)-α-Terpineol |
59.73
(1347) |
60.34
(1348) |
47.6 |
60.45
(1349) |
64.8 |
(+)-α-Terpineol |
60.58
(1356) |
61.14
(1356) |
52.4 |
61.24
(1358) |
35.2 |
(+)-Germacrene D |
73.48
(1518) |
- |
0.0 |
- |
0.0 |
(–)-Germacrene D |
73.73
(1522) |
74.01
(1521) |
100.0 |
74.10
(1522) |
100.0 |
(–)-δ-Cadinene |
76.50
(1563) |
- |
0.0 |
- |
0.0 |
(+)-δ-Cadinene |
77.33
(1576) |
77.67
(1576) |
100.0 |
77.53
(1574) |
100.0 |
(–)-(E)-Nerolidol |
83.40
(1677) |
- |
0.0 |
- |
- |
(+)-(E)-Nerolidol |
83.59
(1680) |
83.96
(1681) |
100.0 |
- |
- |
RT = Retention time (min). RI = Retention index calculated with respect to a homologous series of n-alkanes on a
Restek B-Dex 325 column. EO = Essential oil. ED = Enantiomeric distribution. - = not observed.
There have been no previous reports on the chemical compositions of either C. douglasii or D. canescens essential oils, so direct comparisons cannot be made. Nevertheless, comparisons with other members of the Asteraceae are possible.
Although tiglate esters occur in many essential oils, the occurrence of the free carboxylic acid is rare apparently [21]. Nevertheless, tiglic acid was found in relatively large concentration (18.9%) in the essential oil of Ajuga orientalis (Lamiaceae) from Jordan [22]. The Lamiaceae is known to be a rich source of thymol [23], especially Thymus vulgaris [24], Monarda spp. [25, 26], Origanum tyttanthum [27], and Satureja intermedia [28]. Although the distribution of thymol in the Asteraceae is limited [29], several members of the family have shown relatively high concentrations of thymol in their essential oils, including, for example, Phagnalon sordidum (1.3-11.0%) [30], Tanacetum sinaicum (17.0-18.7%) [31], Tanacetum walteri (22.5%) [32], and Tridex procumbens (20.9-68.9%) [33].
Numerous members of the Asteraceae have been shown to be rich sources of sesquiterpenoids such as (E)-β-caryophyllene (Eclipta prostrata, 47.7% [34]; Duhaldea cappa, 27.5% [35]; and Smallanthus uvedalia, 16.5-24.5% [36]) and germacrene D (Polymnia canadensis, 44.5-63.6% [36]; Verbesina turbacensis, 29.1-36.9% [37]; and Blumea lacera 25.5% [38]). Additionally, comparable to D. canescens essential oil, Calendula arvensis essential oil, depending on the chemotype, has shown high concentrations of epi-cubebol (1.1-15.2%), δ-cadinene (6.0-18.1%), 1-epi-cubenol (0.5-16.3%), and cubenol (0.3-9.2%) [39, 40].
Several
essential oils of members of the Asteraceae have been analyzed by chiral GC-MS
to evaluate their enantiomeric distributions (Table 3). There do not seem to be
any obvious trends in enantiomeric distribution of monoterpene hydrocarbons in
the family. (–)-α-Pinene seems to
predominate in essential oils of Baccharis and Gnoxys essential
oils, but is variable in Artemisia species. The distribution of α-pinene
is not consistent within samples of Artemisia annua [41]. In the case of β-pinene,
the enantiomeric distribution is inconsistent within the genera Artemisia,
Baccharis, and Gnoxys. (+)-Limonene predominated in the essential
oils of Baccharis species, but were not consistent in Ericameria
nauseosa [42]. The oxygenated monoterpenoids
terpenen-4-ol and α-terpineol also do not exhibit consistent
enantiomeric distributions in the family. There are too few data available for
the sesquiterpenes to draw any conclusive trends.
Table 3. Enantiomeric distribution of terpenoids in essential oils of the Asteraceae.
Essential
oil |
α-Pinene |
β-Pinene |
Limonene |
cis-Sabinene hydrate |
trans-Sabinene hydrate |
Terpinen-4-ol |
α-Terpineol |
Germacrene
D |
δ-Cadinene |
(E)-Nerolidol |
Ref. |
||||||||||
(+) |
(–) |
(+) |
(–) |
(+) |
(–) |
(+) |
(–) |
(+) |
(–) |
(+) |
(–) |
(+) |
(–) |
(+) |
(–) |
(+) |
(–) |
(+) |
(–) |
||
Achillea ligustica |
59.0 |
41.0 |
2.0 |
98.0 |
- |
- |
- |
- |
- |
- |
56.0 |
44.0 |
- |
- |
- |
- |
- |
- |
- |
- |
[43] |
Achillea millefolium |
3.0-79.0 |
21.0-97.0 |
0.0-2.0 |
98.0-100.0 |
- |
- |
- |
- |
- |
- |
- |
- |
- |
- |
- |
- |
- |
- |
- |
- |
[44] |
Artemisia annua |
20.0-96.4 |
3.6-80.0 |
0.0 |
100.0 |
0.0 |
100.0 |
- |
- |
- |
- |
- |
- |
- |
- |
- |
- |
- |
- |
- |
- |
[41] |
Artemisia dracunculus |
96.2 |
3.9 |
34.0 |
66.0 |
78.0 |
22.0 |
- |
- |
- |
- |
- |
- |
43.4 |
56.6 |
0.0 |
100.0 |
- |
- |
0.0 |
100.0 |
[45] |
Artemisia tridentata |
100.0 |
0.0 |
100.0 |
0.0 |
- |
- |
- |
- |
- |
- |
25.7-29.8 |
70.2-74.3 |
- |
- |
- |
- |
0.0 |
100.0 |
7.9-8.1 |
91.9-92.1 |
[46] |
Baccharis dracunculifolia |
31.0-44.4 |
55.6-69.0 |
25.4-43.8 |
56.2-74.6 |
63.0-80.5 |
19.5-37.0 |
- |
- |
- |
- |
35.0-42.0 |
58.0-65.0 |
51.0-68.0 |
32.0-49.0 |
- |
- |
- |
- |
- |
- |
[47] |
Baccharis microdonta |
33.1-36.6 |
63.4-66.9 |
41.7-49.9 |
50.1-58.3 |
70.2-85.4 |
14.6-29.8 |
- |
- |
- |
- |
30.0-38.9 |
61.1-70.0 |
56.0-81.0 |
19.0-44.0 |
- |
- |
- |
- |
- |
- |
[47] |
Baccharis tridentata |
4.0 |
96.0 |
73.0 |
27.0 |
66.2 |
33.8 |
- |
- |
- |
- |
- |
- |
- |
- |
- |
- |
- |
- |
- |
- |
[48] |
Chaenactis douglasii |
75.7 |
24.3 |
0.0 |
100.0 |
- |
- |
- |
- |
- |
|
- |
- |
52.4 |
47.6 |
0.0 |
100.0 |
100.0 |
0.0 |
100.0 |
0.0 |
[This work] |
Chrysothamnus
viscidiflorus |
5.5 |
94.5 |
0.2 |
99.8 |
92.3 |
7.7 |
86.1 |
13.9 |
90.5 |
9.5 |
71.9 |
28.1 |
12.6 |
87.4 |
33.4 |
66.6 |
- |
- |
- |
- |
[15] |
Coreopsis triloba |
18.4 |
81.6 |
100.0 |
0.0 |
2.5 |
97.5 |
- |
- |
- |
- |
- |
- |
- |
- |
0.0 |
100.0 |
- |
- |
- |
- |
[49] |
Dieteria canescens |
9.7 |
90.3 |
9.6 |
90.4 |
95.8 |
4.2 |
13.1 |
86.9 |
15.0 |
85.0 |
33.2 |
66.8 |
35.2 |
64.8 |
0.0 |
100.0 |
100.0 |
0.0 |
- |
- |
[This work] |
Diplosthephium juniperinum |
100.0 |
0.0 |
3.4 |
96.6 |
- |
- |
- |
- |
- |
- |
71.6 |
28.4 |
- |
- |
7.7 |
92.3 |
- |
- |
- |
- |
[50] |
Erechtites hieracifolia |
100.0 |
0.0 |
10.3 |
89.7 |
0.0 |
100.0 |
- |
- |
- |
- |
- |
- |
- |
- |
- |
- |
- |
- |
- |
- |
[51] |
Ericameria nauseosa |
9.4-41.5 |
59.5-90.6 |
0.4-10.4 |
89.6-99.6 |
4.2-59.8 |
40.2-95.8 |
19.8-22.7 |
77.3-80.2 |
20.9-22.1 |
77.9-79.1 |
31.4-34.1 |
65.8-68.6 |
0.0-32.7 |
67.3-100.0 |
- |
- |
- |
- |
- |
- |
[42] |
Gynoxys buxifolia |
0.0 |
100.0 |
0.0 |
100.0 |
- |
- |
- |
- |
- |
- |
0.0 |
100.0 |
- |
- |
- |
- |
- |
- |
- |
- |
[52] |
Gynoxys miniphylla |
0.9 |
99.1 |
44.1 |
55.9 |
- |
- |
- |
- |
- |
- |
- |
- |
- |
- |
4.5 |
95.5 |
- |
- |
- |
- |
[53] |
Gynoxys rugulosa |
37.1 |
62.9 |
100.0 |
0.0 |
- |
- |
- |
- |
- |
- |
57.4 |
42.6 |
49.9 |
50.1 |
95.5 |
4.5 |
- |
- |
- |
- |
[54] |
Solidago canadensis |
73.9 |
26.1 |
36.4 |
63.6 |
97.7 |
2.3 |
- |
- |
- |
- |
- |
- |
- |
- |
72.4 |
27.6 |
- |
- |
- |
- |
[55] |
Tagetes maxima |
88.3 |
11.7 |
57.6 |
42.4 |
95.6 |
4.4 |
- |
- |
- |
- |
- |
- |
- |
- |
- |
- |
- |
- |
- |
- |
[56] |
4. Conclusions
This is the first report on the volatile phytochemicals found in Chaenactis douglasii and Dieteria canescens. The essential oil yield for C. douglasii was very low and the essential oil was dominated by tiglic acid and thymol. The presence of thymol may account for the reported antimicrobial effects of C. douglasii extracts. The essential oil of D. canescens, however, was rich in both sesquiterpene hydrocarbons and oxygenated sesquiterpenoids. The enantiomeric distributions of chiral monoterpenoids in these essential oils do not show trends consistent with other members of the Asteraceae. Several genotypes (ecotypes) have been described for C. douglasii and D. canescens, so it is likely that different chemotypes are also possible. Future research should be carried out on C. douglasii and D. canescens from other geographical locations and habitats to describe the phytochemical types of these species more completely.
Authors’
contributions
Conceptualization, W.N.S.; Methodology, P.S. and W.N.S.; Software, P.S.; Validation, W.N.S., Formal Analysis, P.S., A.P., and W.N.S.; Investigation, P.S., A.P., K.S., and W.N.S.; Resources, P.S. and W.N.S.; Data Curation, W.N.S.; Writing – Original Draft Preparation, W.N.S.; Writing – Review & Editing, P.S., A.P., K.S., and W.N.S.; Project Administration, W.N.S.
Acknowledgements
This work was carried out as part of the activities of the Aromatic Plant Research Center (APRC, https://aromaticplant.org/). We are grateful to Daniel Murphy, Collections Curator, Idaho Botanical Garden, for identification of the plants in the Garden.
Funding
This research received no specific grant from any funding agency.
Availability of data and materials
All
data will be made available on request according to the journal policy.
Conflicts of interest
The
authors declare no conflict of interest.
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Abstract
Chaenactis
douglasii and Dieteria canescens are two members of
the Asteraceae found in western North America and utilized by Native Americans
as herbal medicines. The purpose of this investigation was to examine
previously unstudied/understudied volatile phytochemistry of members of the
Asteraceae from southwestern Idaho as well as to extend our understanding of
the properties of Native American aromatic medicinal plants. The essential oils
from the fresh aerial parts were obtained by hydrodistillation and analyzed by
gas chromatographic methods. The colorless essential oil of C. douglasii
was obtained in 0.024% yield, while D. canescens gave a pale-yellow
essential oil in 0.418% yield. Tiglic acid (35.9%) dominated the essential oil
of C. douglasii, followed by thymol (8.4%), δ-cadinene
(5.0%), and 8α-acetoxyelemol (4.7%). There was also a large
concentration of an unidentified component (RI = 1998, 8.7%). The major
components in D. canescens essential oil were δ-cadinene
(28.3%), epi-cubebol (24.4%), 1-epi-cubenol (10.9%), and cubenol
(7.7%). (–)-β-Pinene, (–)-germacrene D, (+)-δ-cadinene, and (+)-(E)-nerolidol
were the exclusive enantiomers found in C. douglasii essential oil,
while (+)-α-pinene (75.7%) was the major enantiomer for α-pinene. In D.
canescens essential oil, the (–)-enantiomers were predominant for α- and
β-pinene (90.3% and 90.4%, respectively), cis- and trans-sabinene
hydrate (86.9% and 85.0%, respectively), terpinen-4-ol (66.8%), α-terpineol
(64.8%), and germacrene D (100%), while the (+)-enantiomer was the major for
limonene (95.8%) and δ-cadinene (100%). A perusal of the literature reveals there
to be no obvious trends in enantiomeric distributions of terpenoids in the
Asteraceae.
Abstract Keywords
Douglas’
dustymaiden, hoary tansyaster, Asteraceae, enantiomeric distribution, gas chromatography,
chiral
This work is licensed under the
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4.0
License (CC BY-NC 4.0).
Editor-in-Chief
Prof. Dr. Radosław Kowalski
This work is licensed under the
Creative Commons Attribution 4.0
License.(CC BY-NC 4.0).