1.   Introduction

Achillea millefolium L. (Asteraceae) is a polymorphous species with a complex taxonomy [1, 2]. World Flora Online currently lists 161 synonyms for the species [3]. The plant is native to the temperate regions of the northern hemisphere, including Europe, western Asia, and North America [4], but has been introduced and cultivated worldwide. The plant is characterized by deeply divided pubescent leaves with flowers gathered in capitula, which are grouped in corymbs (Fig. 1). The western North American plant, known as Achillea millefolium var. occidentalis DC. (western yarrow), ranges from western Canada, south through the Dakotas, Colorado, and New Mexico, and into northern Mexico; and west to the Pacific Coast [5]. The Flora of North America, however, does not recognize infraspecific taxa of A. millefolium [6].

Figure 1. Achillea millefolium var. occidentalis. A: Photograph of plant

(by K. Swor). B: Scan of pressed plant (by W.N. Setzer).

Achillea millefolium has been used in traditional medicine throughout its global distribution [7]. The Shoshoni Native Americans applied a poultice of the boiled whole plant externally to treat sores, while a decoction of the plant was used as a liniment for sores and rashes. The Shoshoni prepared a decoction of the plant and took it to treat colds [8]. Similarly, the Paiute took an infusion of A. millefolium as a cough medicine [9]. In Europe, the plant is traditionally taken orally for gastrointestinal disorders or used topically to treat skin disorders [1]. In Iran, the plant is used for menstruation problems, to stimulate menstruation, to stop bleeding, for wound healing, to relieve asthma and constipation, and as diuretic, anthelmintic, and carminative [10]. In Colombia and Peru, A. millefolium is used to relieve gastrointestinal problems such as indigestion, flatulence, colitis, and gastritis [11]. The whole plant is used in Colombia to treat skin disorders, including acne, boils, botfly infestations, skin ulcers, and sores [11].

Achillea millefolium has been shown to be a source of sesquiterpene lactones, including 8-acetylegelolide, 8-angeloylegelolide, 8-angeloyloxyleucodin, acetylbalchanolide, achillicin, achillin, achillinin A, achillifolin, badkhyzin, millefin, millifolide C, isoachifolidiene, leukodin, dihydroparthenolide, and balchanolide; several polyacetylenes such as anacycline, dehydroanacycline, 2,9-pentadecadiene-12,14-diynoic acid isobutylamide, 2,4-tetradecadiene-8,10-diynoic acid 3-methylbutylamide, 2,4-undecadiene-8,10-diynoic acid 2,3-dehydropiperidide, and 2,4-undecadiene-8,10-diynoic acid isobutylamide; and flavonoids apigenin, artemetin, casticin, centauredidin, chrysoeriol, isorhamnetin, luteolin, and quercetin, as well as an azulene-containing essential oil [1, 7, 12, 13].

Although the taxonomic treatment in Flora of North America suggests little support for infraspecific taxa [6], it was deemed important to examine the essential oil compositions of several samples of A. millefolium collected in the wild from several locations in the Great Basin area of western North America to test the hypothesis that chemical composition differences may differentiate the A. millefolium var. occidentalis from Old World samples of A. millefolium.

2. Materials and methods  

2.1. Plant material

Aerial parts of A. millefolium were collected from six individual plants growing in southern Idaho and eastern Oregon (Table 1). The plants were identified by W.N. Setzer in the field and verified by comparison with samples from the New York Botanical Garden [14]. Voucher specimens (WNS-Amo-5675 and WNS-Amo-7746) have been deposited at the University of Alabama in Huntsville herbarium. The fresh aerial parts were frozen and stored frozen (–20 °C) until processed.

2.2. Essential oil

For each sample of A. millefolium, the fresh/frozen aerial parts were finely chopped and hydrodistilled for three hours using a Likens-Nickerson apparatus [15–17] with continuous extraction of the distillate with dichloromethane to give the essential oils (Table 1).

Table 1. Collection and hydrodistillation details of Achillea millefolium var. occidentalis.

Sample Number	Collection Date	Collection Site	Mass of Plant Material (g)	Mass of Essential Oil (mg)	Essential Oil Color
#1	28 June 2022	Anderson Ranch, Idaho 43°24′20″N, 115°17′33″W, 1423 m asl	73.21	236.2	deep blue
#2	7 July 2022	Bogus Basin, Idaho 43°43′58″N, 116°7′42″W, 1673 m asl	74.48	198.5	deep blue
#3	27 May 2023	Leslie Gulch, Oregon 43°18’13”N, 117°17’17”W, 971 m asl	98.25	1034.4	deep blue
#4	8 August 2023	Redfish Lake, Idaho 44°8’40”N, 114°54’42”W, 2001 m asl	83.14	145.9	yellow
#5	11 August 2023	Silver City, Idaho 43°2’37”N, 116°46’33”W, 1788 m asl	59.75	563.0	blue
#6	26 August 2023	Boise Foothills, Idaho 43°41′20″N, 116°2′48″W, 1355 m asl	32.76	475.7	deep blue

2.3. Gas chromatographic analysis

The A. millefolium essential oils were analyzed by GC-MS, GC-FID, and enantioselective GC-MS as previously reported [18].

2.4. Hierarchical cluster analysis

Hierarchical cluster analysis (HCA) was carried out using XLSTAT v. 2018.1.1.62926 (Addinsoft, Paris, France). The concentrations of the 28 most abundant components (α-pinene, camphene, sabinene, β-pinene, yomogi alcohol, p-cymene, 1,8-cineole, artemisia ketone, γ-terpinene, cis-sabinene hydrate, terpinolene, α-thujone, β-thujone, camphor, borneol, terpinen-4-ol, α-terpineol, chrystanthenyl acetate, bornyl acetate, α-copaene, (E)-β-caryophyllene, germacrene D, (E)-nerolidol, spathulenol, caryophyllene oxide, γ-eudesmol, α-eudesmol, and chamazulene) from this study as well as previously reported compositions from the literature [19–52] and commercial samples from the Aromatic Plant Research Center (APRC) collection were used for the analysis. Dissimilarity was used to determine clusters considering Euclidean distance and Ward’s method was used to define agglomeration. 

3.   Results and discussion

Hydrodistillation of A. millefolium samples #1-#6 gave essential oils in yields of 0.323%, 0.267%, 1.053%, 0.175%, 0.942%, and 1.452%, respectively. Samples #1 and #2 showed the lowest yields; sample #6 showed the highest yield. It is not known what factors may be responsible for the yield variations; the samples were collected in different years, however, with the 2022 samples showing lower yields than the 2023 samples. The gas chromatographic analysis allowed the determination of a total of 152 compounds, which accounted for 95.0-99.1% of the compositions (Table 2).

Table 2. Chemical compositions (percent of total) of Achillea millefolium var. occidentalis essential oils.

RIcalc	RIdb	Compounds	#1	#2	#3	#4	#5	#6
847	846	(Z)-Salvene	-	-	0.1	-	-	-
874	873	2-Methylbutyl acetate	-	-	0.3	-	-	-
902	902	Santolina triene	-	0.1	0.3	-	0.1	-
922	922	Artemisia triene	-	-	0.2	tr	tr	-
923	923	Tricyclene	tr	tr	-	tr	0.1	0.3
925	927	α-Thujene	tr	tr	0.2	tr	0.2	0.1
932	932	α-Pinene	0.3	0.4	0.9	0.2	1.4	2.2
945	942	5,5-Dimethylbut-3-enolide	tr	tr	-	-	0.1	-
949	950	Camphene	0.4	1.0	0.1	0.4	1.7	7.3
960	959	Benzaldehyde	tr	tr	0.1	0.1	0.1	tr
969	967	Isoamyl propionate	-	tr	0.1	-	tr	tr
972	972	Sabinene	3.2	1.1	3.1	0.8	2.3	0.7
977	978	β-Pinene	0.5	0.5	2.2	0.3	6.3	1.6
988	989	Myrcene	0.1	0.1	0.2	tr	0.1	0.1
989	990	Dehydro-1,8-cineole	0.1	tr	0.1	0.1	0.2	0.1
995	996	Yomogi alcohol	-	1.0	8.8	2.1	3.6	tr
1015	1015	Isoamyl isobutyrate	0.1	0.1	0.3	0.1	0.1	0.1
1017	1017	α-Terpinene	0.2	0.2	1.9	1.1	1.5	0.1
1024	1025	p-Cymene	0.1	0.5	2.6	1.1	4.3	0.7
1028	1026	2-Acetyl-3-methylfuran	-	-	-	0.1	tr	tr
1029	1030	Limonene	0.2	0.4	0.3	0.1	1.1	0.5
1030	1031	β-Phellandrene	tr	tr	0.1	tr	0.1	tr
1032	1032	1,8-Cineole	10.8	7.5	7.6	16.4	10.7	5.3
1035	1036	Benzyl alcohol	-	-	0.1	0.2	-	-
1037	1034	Lavender lactone	-	-	-	-	0.1	tr
1042	1043	Phenylacetaldehyde	0.1	0.1	tr	0.1	0.2	0.2
1058	1056	Artemisia Ketone	-	-	4.2	5.7	18.7	-
1059	1058	γ-Terpinene	0.5	1.9	4.2	1.4	-	0.4
1069	1069	cis-Sabinene hydrate	0.7	1.9	1.1	4.4	1.0	1.4
1079	1079	Artemisia alcohol	-	2.0	3.8	0.2	1.0	-
1085	1086	Terpinolene	0.1	0.1	0.7	0.8	0.6	0.1
1095	1096	Methyl benzoate	-	-	0.1	0.2	-	-
1100	1101	Linalool	0.8	1.0	-	-	0.1	tr
1101	1101	trans-Sabinene hydrate	-	0.3	0.7	2.2	0.6	0.5
1103	1103	2-Methylbutyl isovalerate	-	0.8	1.1	-	0.5	0.5
1103	1104	Hotrienol	-	-	-	-	0.3	0.1
1105	1104	Nonanal	-	-	-	0.1	0.1	tr
1106	1105	α-Thujone	40.5	0.1	15.0	-	-	-
1108	1103	2-Methylbutyl isovalerate	-	-	-	0.1	tr	tr
1112	1111	Phenethyl alcohol	0.1	0.2	0.2	-	-	-
1118	1118	β-Thujone	5.6	tr	1.8	-	-	-
1120	1118	Dehydrosabina ketone	-	-	-	0.1	tr	-
1121	1122	trans-p-Mentha-2,8-dien-1-ol	tr	tr	tr	0.1	0.1	0.1
1124	1124	cis-p-Menth-2-en-1-ol	0.1	0.1	0.5	1.3	0.5	0.1
1126	1126	α-Campholenal	tr	tr	-	0.1	0.1	0.2
1130	1131	Limona ketone	tr	-	-	tr	tr	-
1136	1138	cis-p-Mentha-2,8-dien-1-ol	tr	-	-	-	0.1	0.1
1139	1139	Nopinone	-	-	-	-	0.1	-
1140	1140	trans-Sabinol	0.3	-	0.1	-	-	-
1141	1141	trans-Pinocarveol	-	-	0.1	0.4	0.1	0.4
1142	1142	trans-p-Menth-2-en-1-ol	0.1	0.1	0.3	1.0	0.4	tr
1148	1149	Camphor	7.2	19.4	0.5	15.8	8.8	59.6
1155	n.a.	3,3,6-Trimethyl-4,5-heptadien-2-one	-	-	-	0.2	-	-
1156	1155	trans-Chrysanthemol	-	0.9	-	-	0.1	-
1157	1157	Sabina ketone	0.1	-	-	0.2	0.1	0.1
1159	1165	iso-Borneol	0.1	-	-	-	-	-
1160	1162	(Z)-iso-Citral	-	-	-	0.1	-	-
1162	1164	Pinocarvone	0.1	tr	-	0.4	0.3	0.6
1164	1164	β-Artemisyl acetate	0.1	1.6	3.8	0.9	1.5	-
1169	1168	α-Phellandrene epoxide	0.1	-	-	-	-	-
1170	1170	δ-Terpineol	0.2	-	0.1	0.5	0.1	0.1
1172	1173	Borneol	0.6	3.5	-	0.3	0.7	1.3
1181	1180	Terpinen-4-ol	1.7	2.4	9.0	23.4	8.9	0.9
1183	1183	Thuj-3-en-10-al	0.1	-	-	-	0.1	tr
1187	1186	p-Cymen-8-ol	tr	tr	tr	0.1	0.2	0.1
1188	1191	1-Dodecene	0.1	-	-	-	-	-
1195	1195	α-Terpineol	2.5	2.9	1.1	1.8	0.8	0.3
1196	1196	Myrtenal	-	-	-	-	0.9	0.7
1198	1187	Cryptone	0.2	0.1	-	-	0.2	0.1
1198	1196	cis-Piperitol	-	-	0.1	0.1	-	-
1207	1208	Verbenone	-	-	-	-	-	0.1
1208	1207	(3E)-Octenyl acetate	0.1	-	-	-	-	-
1208	1208	trans-Piperitol	0.1	tr	0.2	-	-	-
1218	1217	7-Ethylidene-bicyclo[3.3.0]octan-3-one	0.3	-	-	0.1	-	-
1237	1237	Pulegone	-	-	-	-	0.1	-
1240	1240	Ascaridole	-	-	-	0.1	-	-
1241	1242	Cuminal	0.1	-	-	0.1	0.1	-
1243	1242	Carvone	-	-	-	-	0.1	0.1
1269	1264	2,5-Bornanedione	-	-	-	-	-	0.1
1272	1266	Chrystanthemyl acetate	-	3.4	0.1	0.1	0.1	0.6
1283	1284	Lavandulyl acetate	-	-	0.4	0.1	0.1	-
1284	1285	Bornyl acetate	0.6	5.4	0.1	0.7	1.7	2.2
1287	1286	trans-Sabinyl acetate	0.3	-	0.3	-	-	-
1290	1291	p-Cymen-7-ol	0.1	0.1	0.1	-	-	-
1296	1296	Terpin-1-en-4-yl acetate	-	-	0.1	0.1	0.2	-
1298	1300	Carvacrol	-	tr	0.1	0.1	0.1	tr
1304	1306	iso-Ascaridole	-	-	-	0.1	tr	-
1327	1327	p-Mentha-1,4-dien-7-ol	0.2	tr	-	-	-	-
1334	1335	δ-Elemene	0.1	-	-	-	-	-
1352	1356	Eugenol	0.4	0.6	0.2	0.3	0.2	0.1
1356	1349	α-Terpinyl acetate	0.1	-	-	-	-	-
1358	1361	Neryl acetate	-	0.1	-	-	-	-
1367	1367	Cyclosativene	-	0.1	-	-	-	-
1374	1375	α-Copaene	-	0.2	0.2	0.1	-	0.1
1377	1378	Geranyl acetate	-	0.3	-	-	-	-
1383	1385	(E)-Jasmone	0.1	0.1	-	0.1	-	-
1384	1384	Benzyl pentanoate	0.1	0.2	0.1	tr	-	-
1386	1385	α-Isocomene	0.1	-	-	-	-	0.1
1388	1390	trans-β-Elemene	tr	0.1	-	-	-	tr
1391	1392	(Z)-Jasmone	0.2	1.0	0.2	0.2	0.1	tr
1396	1396	(2E)-1,3,7-Trimethyl-2,6-octadienyl acetate	-	0.4	-	-	0.1	-
1410	1413	β-Isocomene	0.1	-	-	-	-	-
1419	1417	(E)-β-Caryophyllene	0.6	1.7	0.5	0.2	0.5	0.5
1453	1452	(E)-β-Farnesene	0.1	0.1	0.2	0.1	0.1	0.1
1455	1454	α-Humulene	0.1	0.3	0.1	tr	0.1	0.1
1481	1480	Germacrene D	2.0	2.6	3.2	1.8	1.6	1.5
1483	1483	Davana ether 1	0.1	0.1	-	-	-	-
1484	1483	Phenethyl 2-methylbutyrate	-	0.1	0.1	-	0.1	0.1
1488	1489	β-Selinene	-	-	-	-	-	0.1
1491	1489	(Z,E)-α-Farnesene	-	0.1	-	-	-	-
1494	1497	Bicyclogermacrene	0.1	0.1	0.2	0.1	0.1	0.1
1494	1497	α-Selinene	-	-	-	-	-	0.1
1498	1497	α-Muurolene	-	0.3	0.2	tr	-	0.1
1502	1502	Davana ether 2	0.3	0.2	-	-	-	-
1504	1504	Davana ether 3	0.1	-	-	-	-	-
1504	1503	(E,E)-α-Farnesene	tr	0.1	0.2	-	tr	-
1512	1512	γ-Cadinene	tr	tr	tr	-	-	0.1
1514	1515	Cubebol	-	-	tr	-	-	0.1
1517	1518	δ-Cadinene	0.1	0.2	0.1	0.1	0.1	0.2
1521	1521	Davana ether 4	0.2	0.1	-	-	-	-
1523	1523	β-Sesquiphellandrene	0.1	-	0.1	-	-	-
1547	1549	α-Elemol	0.1	-	0.4	0.5	-	-
1560	1561	(E)-Nerolidol	5.7	13.5	4.4	0.4	1.4	0.5
1569	1570	Neryl 2-methylbutanoate	0.3	-	0.1	tr	0.1	-
1572	1569	Longipinocarvone	0.2	0.2	-	0.3	0.5	0.3
1577	1580	Neryl isovalerate	0.3	-	0.3	0.1	0.1	0.2
1581	1587	Caryophyllene oxide	0.7	0.8	0.5	0.5	1.3	1.0
1591	1593	Salvial-4(14)-en-1-one	-	-	-	0.1	0.1	-
1597	1597	Fokienol	-	0.8	0.8	0.1	0.7	0.2
1608	1613	Copaborneol	-	0.3	0.2	-	-	-
1610	1613	Humulene epoxide II	-	-	-	-	tr	tr
1612	1609	Rosifoliol	-	-	0.2	0.1	-	-
1621	1632	Humulenol II	-	-	-	0.5	1.7	0.7
1629	1627	Eremoligenol	-	-	0.4	0.1	-	-
1631	1632	γ-Eudesmol	-	-	3.0	-	-	-
1632	1630	Caryophylla-4(12),8(13)-dien-5α-ol	0.2	0.3	0.3	0.2	0.8	0.5
1635	1635	Caryophylla-4(12),8(13)-dien-5β-ol	0.5	0.4	0.4	0.6	0.8	0.4
1641	1643	τ-Cadinol	-	-	-	-	-	0.4
1642	1642	Methyl (Z)-jasmonate	0.1	0.9	0.2	-	0.2	0.1
1654	1655	α-Eudesmol	-	-	0.7	3.0	-	0.1
1655	1655	α-Cadinol	0.4	0.3	-	-	-	0.1
1671	1671	14-Hydroxy-9-epi-(E)-caryophyllene	-	-	-	0.5	-	0.1
1680	1676	8-Hydroxyisobornyl isobutanoate	-	-	-	0.2	1.2	0.6
1684	1683	Germacra-4(15),5,10(14)-trien-1α-ol	-	-	0.3	1.3	-	-
1716	1716	(2E,6E)-Farnesol	-	0.1	0.2	0.1	-	-
1730	1730	Chamazulene	4.4	7.0	0.8	-	0.7	0.8
1775	1784	Dehydrochamazulene	-	0.1	-	-	-	-
1832	1832	(2Z,6E)-Farnesyl acetate	-	0.1	-	-	-	-
1932	1938	Pellitorine	-	-	-	-	-	0.4
2300	2300	Tricosane	0.1	0.1	-	0.1	0.1	tr
2500	2500	Pentacosane	0.1	0.1	-	0.1	0.1	0.1
2700	2700	Heptacosane	0.1	0.1	-	0.1	0.1	tr
		Compound Classes
		Monoterpene hydrocarbons	5.7	6.5	17.0	6.2	19.7	13.8
		Oxygenated monoterpenoids	74.3	53.8	60.3	79.7	64.0	75.8
		Sesquiterpene hydrocarbons	7.8	12.8	5.7	2.2	3.1	3.8
		Oxygenated sesquiterpenoids	8.5	17.3	11.7	8.3	7.2	4.3
		Benzenoid aromatics	0.6	1.1	0.8	0.8	0.5	0.4
		Others	1.1	3.5	2.3	1.0	1.7	1.1
		Total identified	97.9	95.0	97.8	98.2	96.2	99.1

RIcalc = Retention index determined using a homologous series of n-alkanes on a ZB-5ms column [53]. RIdb = Reference retention

index from the databases [54–57]. tr = trace (< 0.05%). - = not detected. Major components are highlighted in bold.

The major components were camphor (0.5-59.6%, mean 18.5%), α-thujone (0.0-40.5%, mean 9.3%), terpinen-4-ol (0.9-23.4%, mean 7.7%), artemisia ketone (0.0-18.7%, mean 4.8%), 1,8-cineole (5.3-16.4%, mean 9.7%), (E)-nerolidol (0.4-13.5%, mean 4.3%), yomogi alcohol (0.0-8.8%, mean 2.6%), camphene (0.1-7.3%, mean 1.8%), chamazulene (0.0-7.0%, mean 2.3%), β-pinene (0.3-6.3%, mean 1.2%), β-thujone (0.0-5.6%, mean 1.2%), and bornyl acetate (0.1-5.4%, mean 1.8%). The A. millefolium essential oil compositions show little similarity. However, samples #1 and #3 were rich in α-thujone, samples #2 and #6 were rich in camphor, and samples #4 and #5 were rich in terpinen-4-ol. Essential oil samples #1, #2, #3, #5, and #6 were blue in color, owing to the presence of chamazulene. Essential oil sample #4, which lacked chamazulene, was yellow in color.

In order to compare the essential oil compositions of the Great Basin samples in this work with the chemical compositions of A. millefolium from Old World locations, a hierarchical cluster analysis was carried out based on the 28 most abundant components. The cluster analysis shows much variation in essential oil compositions (Fig. 2), but four major groupings are evident: (1) a germacrene D/sabinene group, (2) a β-pinene/caryophyllene oxide group, (3) a 1,8-cineole/camphor group, and (4) a chamazulene group. Great Basin samples #1, #2, #4, #5, and #6 fall into the 1,8-cineole/camphor group, while sample #3 falls into the β-pinene/caryophyllene oxide group. Interestingly, the 1,8-cineole/camphor group is dominated by samples from Iran. The β-pinene/caryophyllene oxide group, on the other hand, is dominated by samples from Europe. It is apparent that there is much chemical diversity in the essential oils of A. millefolium and that essential oil chemical compositions cannot distinguish New World (i.e., var. occidentalis) samples of A. millefolium from Old World samples.

Figure 2. Dendrogram based on hierarchical cluster analysis of Achillea millefolium essential oil compositions

Kokkalou and co-workers had noted wide variation in A. millefolium essential oil compositions when comparing samples of European origin with samples cultivated in North America [38]. Likewise, Farajpour and co-workers had observed wide variation in A. millefolium essential oil compositions from Iran [58]. These investigators identified five chemotypes: 1,8-cineole/(E)-nerolidol, high cubenol, high germacrene-D/isospathulenol, high camphor/cubenol, and high 1,8-cineole/ β-thujone/cubenol. Furthermore, Raudone and co-workers investigated different morphotypes of A. millefoium and found notable differences in triterpenoid and phenolic components [2].

The A. millefolium essential oils were analyzed by enantioselective GC-MS (Table 3). The dominant enantiomers were (–)-α-pinene (83.2 ± 5.4%), (–)-camphene (98.5 ± 2.2%), (–)-β-pinene (89.5 ± 6.1%), and (–)-α-terpineol (81.8 ± 4.3%). Sabinene, limonene, cis-sabinene hydrate, and trans-sabinene hydrate had variable enantiomeric distributions. The sesquiterpenoids (–)-(E)-β-caryophyllene, (–)-germacrene D, and (+)-(E)-nerolidol were the only enantiomers observed. (–)-Camphor was the only enantiomer observed. When detected, only (–)-β-phellandrene, (–)-α-thujone, (+)-β-thujone, and (–)-borneol were observed. Orth and co-workers carried out enantioselective GC-MS on A. millefolium from Kaliningrad [43]. These investigators found (–)-β-pinene to dominate, but sabinene and α-pinene distributions were variable, although (–)-sabinene and (–)-α-pinene were often dominant.

Table 3. Enantiomeric distribution (percent of each enantiomer) of chiral terpenoid components in Achillea millefolium var. occidentalis.

Compounds	RIdb	RIcalc	#1	#2	#3	#4	#5	#6
(+)-α-Thujene	950	950	nd	nd	24.2	nd	0.0	nd
(–)-α-Thujene	951	951	nd	nd	75.8	nd	100.0	nd
(–)-α-Pinene	976	977	72.8	85.7	82.0	86.0	85.4	87.3
(+)-α-Pinene	982	983	27.2	14.3	18.0	14.0	14.6	12.7
(–)-Camphene	998	1000	100.0	100.0	94.3	99.2	98.2	99.3
(+)-Camphene	1005	1003	0.0	0.0	5.7	0.8	1.8	0.7
(+)-Sabinene	1021	1020	56.1	11.8	47.2	15.7	42.6	15.8
(–)-Sabinene	1030	1029	43.9	88.2	52.8	84.3	57.4	84.2
(+)-β-Pinene	1027	1027	18.8	10.5	10.6	7.7	1.1	14.6
(–)-β-Pinene	1031	1031	81.2	89.5	89.4	92.3	98.9	85.4
(–)-Limonene	1073	1074	68.9	83.1	78.9	80.4	31.8	74.7
(+)-Limonene	1081	1081	31.1	16.9	21.1	19.6	68.2	25.3
(–)-β-Phellandrene	1083	1082	nd	nd	100.0	nd	100.0	nd
(+)-β-Phellandrene	1089	nd	nd	nd	0.0	nd	0.0	nd
(+)-cis-Sabinene hydrate	1199	1199	75.4	88.1	7.7	16.8	23.8	79.1
(–)-cis-Sabinene hydrate	1202	1201	24.6	11.9	92.3	83.2	76.2	20.9
(+)-α-Thujone	1213	nd	0.0	0.0	0.0	nd	nd	nd
(–)-α-Thujone	1222	1221	100.0	100.0	100.0	nd	nd	nd
(–)-Linalool	1228	1231	100.0	16.5	nd	nd	nd	nd
(+)-Linalool	1231	1234	0.0	83.5	nd	nd	nd	nd
(+)-trans-Sabinene hydrate	1231	1229	nd	nd	8.1	25.9	18.5	61.5
(–)-trans-Sabinene hydrate	1235	1233	nd	nd	91.9	74.1	81.5	38.5
(+)-β-Thujone	1230	1232	100.0	nd	100.0	nd	nd	nd
(–)-β-Thujone	na	nd	0.0	nd	0.0	nd	nd	nd
(–)-Camphor	1253	1254	100.0	100.0	100.0	100.0	100.0	100.0
(+)-Camphor	1259	nd	0.0	0.0	0.0	0.0	0.0	0.0
(+)-Terpinen-4-ol	1297	1295	60.5	59.3	26.1	21.5	31.0	61.5
(–)-Terpinen-4-ol	1300	1297	39.5	40.7	73.9	78.5	69.0	38.5
(–)-Borneol	1335	1336	100.0	100.0	nd	nd	100.0	100.0
(+)-Borneol	1340	nd	0.0	0.0	nd	nd	0.0	0.0
(–)-α-Terpineol	1347	1346	87.6	86.1	81.7	76.9	78.1	80.7
(+)-α-Terpineol	1356	1355	12.4	13.9	18.3	23.1	21.9	19.3
(–)-(E)-β-Caryophyllene	1461	1462	100.0	100.0	100.0	100.0	100.0	100.0
(+)-(E)-β-Caryophyllene	na	nd	0.0	0.0	0.0	0.0	0.0	0.0
(+)-Germacrene D	1519	nd	0.0	0.0	0.0	0.0	0.0	0.0
(–)-Germacrene D	1522	1523	100.0	100.0	100.0	100.0	100.0	100.0
(–)-(E)-Nerolidol	1677	nd	0.0	0.0	0.0	0.0	0.0	0.0
(+)-(E)-Nerolidol	1680	1679	100.0	100.0	100.0	100.0	100.0	100.0

RIdb = Retention index from our in-house database. RIcalc = Calculated retention index based on a homologous series of n-alkanes on a Restek B-Dex 325 capillary column. na = reference compound not available. nd = compound not detected.

There have been several investigations on enantioselective GC-MS analyses of Asteraceae essential oils. However, there are no obvious trends in the enantiomeric distribution of monoterpene hydrocarbons or of oxygenated monoterpenoids in the family [59]. When detected, (–)-(E)-β-caryophyllene is the only enantiomer observed [60–62]. This enantiomer is found in numerous higher plants, while (+)-(E)-β-caryophyllene is apparently found in liverworts [13]. Likewise, (–)-germacrene D and (+)-(E)-nerolidol are the dominant, if not exclusive, enantiomers found in the Asteraceae [59, 61, 62].

Several of the major components in A. millefolium have shown relevant biological activities. For example, 1,8-cineole, α-thujone, β-thujone, and camphor have shown analgesic-like activity [63, 64]. Camphor and 1,8-cineole have shown antitussive effects in a Guinea-pig model [65]. A combination of (–)-camphor and 1,8-cineole has shown synergistic antimicrobial activity against Candida albicans [66]. Terpinen-4-ol has shown antimicrobial activity against several pathogenic micro-organisms [67]. Terpinen-4-ol has also shown anti-inflammatory effects [68], attributed to suppression of pro-inflammatory cytokine production [69, 70]. (E)-Nerolidol has shown antinociceptive activity involving the GABAergic system and not to the opiodergic or ATP-sensitive K+ channels [71]. Nerolidol has also shown anti-inflammatory activity attributed to suppression of TNF-α and IL-1β pro-inflammatory cytokines [71]. Thus, the bioactivities of the major components in A. millefolium essential oil are consistent with the traditional uses of the plant by Native Americans.

4.   Conclusions

The essential oils of Achillea millefolium var. occidentalis, collected from several sites in the Great Basin of North America, show wide variation in their chemical compositions, including broadly variable concentrations of camphor, α-thujone, terpinen-4-ol, artemisia ketone, 1,8-cineole, and (E)-nerolidol. A survey of the literature also reveals wide variation in A. millefolium essential oil compositions in samples from Europe and Asia. Furthermore, because of the wide variation in essential oil compositions of A. millefolium from the Great Basin as well as the wide variation in compositions from samples of European or Asian origin, essential oil compositions cannot distinguish between New-World and Old-World A. millefolium essential oils. Thus, there is no phytochemical support for infraspecific separation of this species. Future research using DNA barcoding may provide evidence for the separation of infraspecific taxa. Enantioselective gas chromatography has shown (–)-α-pinene, (–)-camphene, (–)-β-pinene, (–)-α-terpineol, (–)-camphor, (–)-β-phellandrene, (–)-α-thujone, (+)-β-thujone, and (–)-borneol to be the dominant monoterpenoid enantiomers in A. millefolium from western North America. However, there are no obvious trends in the enantiomeric distribution of monoterpenoids in the Asteraceae family overall. Additional research using enantioselective gas chromatography may be able to identify trends within individual genera, however.

 

Authors’ contributions

Conceptualization, W.N.S.; Methodology, A.P., P.S., and W.N.S.; Software, P.S.; Validation, W.N.S., Formal Analysis, A.P., and W.N.S.; Investigation, A.P., P.S., 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. 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/).

 

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.

 

References

1.         Bruneton, J. Pharmacognosy; 2nd edition; Intercept Ltd: London, UK, 1999; ISBN 1-898298-63-7.

2.         Raudone, L.; Vilkickyte, G.; Marksa, M.; Radusiene, J. Comparative phytoprofiling of Achillea millefolium morphotypes: Assessing antioxidant activity, phenolic and triterpenic compounds variation across different plant parts. Plants. 2024, 13, 1043. https://doi.org/10.3390/plants13071043.

3.         World Flora Online, W.F.O. Achillea millefolium L. Available online: http://www.worldfloraonline.org/taxon/wfo-0000042097 (accessed on Apr 2, 2023).

4.         Missouri Botanical Garden. Achillea millefolium. Available online: https://www.missouribotanicalgarden.org/PlantFinder/PlantFinderDetails.aspx?taxonid=277129&isprofile=1&basic=yarrow (accessed on Apr 3, 2023).

5.         Winslow, S.R. Western Yarrow, Achillea millefolium L. var. occidentalis DC.; United States Department of Agriculture, Natural Resources Conservation Service, Bridger Plant Materials Center: Bridger, Montana, USA, 2005.

6.         eFloras.org. Flora of North America. Achillea millefolium Linnaeus. Available online: http://www.efloras.org/florataxon.aspx?flora_id=1&taxon_id=200023010 (accessed on Apr 2, 2023).

7.         Ali, S.I.; Gopalakrishnan, B.; Venkatesalu, V. Pharmacognosy, phytochemistry and pharmacological properties of Achillea millefolium L.: A review. Phyther. Res. 2017, 31, 1140–1161. https://doi.org/10.1002/ptr.5840.

8.         Train, P.; Henrichs, J.R.; Archer, W.A. Medicinal Uses of Plants by Indian Tribes of Nevada; U.S. Department of Agriculture: Washington, DC, USA, 1941.

9.         Fowler, C.S. Willard Z. Park’s Ethnographic Notes on the Northern Paiute of Western Nevada 1933-1940; University of Utah Press: Salt Lake City, Utah, USA, 1989.

10.     Bussmann, R.W.; Batsatsashvili, K.; Kikvidze, Z.; Paniagua-Zambrana, N.Y.; Ghorbani, A.; Nasab, F.K.; Khutsishvili, M.; Maisaia, I.; Sikharulidze, S.; Tchelidze, D. Achillea grandiflora M. Bieb. Achillea micrantha Willd. Achillea millefolium L. Achillea nobilis L. Achillea ptarmicifolia (Willd.) Rupr. ex Heimerl Ptarmica ptarmicifolia Galushko. In Ethnobotany of the Mountain Regions of Far Eastern Europe; Batsatsashvili, K., Kikvidze, Z., Bussmann, R.W., Eds.; Springer Nature: Cham, Switzerland, 2020, pp.47–57. ISBN 978-3-030-28939-3.

11.     Paniagua-Zambrana, N.Y.; Bussmann, R.W.; Romero, C. Achillea millefolium L. In Ethnobotany of the Andes; Paniagua-Zambrana, N.Y., Bussmann, R.W., Eds.; Springer Nature: Cham, Switzerland, 2020, pp.111–115 ISBN 978-3-030-28932-4.

12.     Chandler, R.F.; Hooper, S.N.; Harvey, M.J. Ethnobotany and phytochemistry of yarrow, Achillea millefolium, Compositae. Econ. Bot. 1982, 36, 203–223. https://doi.org/10.1007/bf02858720.

13.     Dictionary of Natural Products. Dictionary of Natural Products on USB; CRC Press: Boca Raton, Florida, 2023; ISBN 978-0-412-49150-4.

14.     New York Botanical Garden, N.Y.B.G. C. V. Starr Virtual Herbarium. Available online: https://sweetgum.nybg.org/science/vh/specimen-list/?SummaryData=Achillea millefolium (accessed on Jun 30, 2022).

15.     Likens, S.T.; Nickerson, G.B. Detection of certain hop oil constituents in brewing products. Proceedings. Annu. Meet.  Am. Soc. Brew. Chem. 1964, 22, 5–13. https://doi.org/10.1080/00960845.1964.12006730.

16.     Au-Yeung, C.Y.; MacLeod, A.J. A comparison of the efficiency of the Likens and Nickerson extractor for aqueous, lipid/aqueous, and lipid samples. J. Agric. Food Chem. 1981, 29, 502–505. https://doi.org/10.1021/jf00105a016.

17.     Bouseta, A.; Collin, S. Optimized Likens-Nickerson methodology for quantifying honey flavors. J. Agric. Food Chem. 1995, 43, 1890–1897. https://doi.org/10.1021/jf00055a025.

18.     Satyal, P.; Dosoky, N.S.; Poudel, A.; Swor, K.; Setzer, W.N. Chemical composition of the aerial parts essential oil of Chrysothamnus viscidiflorus from southwestern Idaho. J. Essent. Oil Plant Comp. 2023, 1, 115–121. https://doi.org/10.58985/jeopc.2023.v01i02.16.

19.     Agnihotri, V.K.; Lattoo, S.K.; Thappa, R.K.; Kaul, P.; Qazi, G.N.; Dhar, A.K.; Saraf, A.; Kapahi, B.K.; Saxena, R.K.; Agarwal, S.C. Chemical variability in the essential oil components of Achillea millefolium Agg. from different Himalayan habitats (India). Planta Med. 2005, 71, 280–283. https://doi.org/10.1055/s-2005-837828.

20.     Ahmadi-Dastgerdi, A.; Ezzatpanah, H.; Asgary, S.; Dokhani, S.; Rahimi, E. Phytochemical, antioxidant and antimicrobial activity of the essential oil from flowers and leaves of Achillea millefolium subsp. millefolium. J. Essent. Oil-Bear. Plants. 2017, 20, 395–409. https://doi.org/10.1080/0972060X.2017.1280419.

21.     Ebrahimi, M.; Farajpour, M.; Hadavand, H.; Bahmani, K.; Khodaiyan, F. Essential oil variation among five Achillea millefolium ssp. elbursensis collected from different ecological regions of Iran. Ann. Biol. Res. 2012, 3, 3248–3253.

22.     El-Kalamouni, C.; Venskutonis, P.R.; Zebib, B.; Merah, O.; Raynaud, C.; Talou, T. Antioxidant and antimicrobial activities of the essential oil of Achillea millefolium L. grown in France. Medicines 2017, 4, 30, https://doi.org/10.3390/medicines4020030.

23.     Falconieri, D.; Piras, A.; Porcedda, S.; Marongiu, B.; Gonçalves, M.J.; Cabral, C.; Cavaleiro, C.; Salgueiro, L. Chemical composition and biological activity of the volatile extracts of Achillea millefolium. Nat. Prod. Commun. 2011, 6, 1527–1530. https://doi.org/10.1177/1934578x1100601030.

24.     Farhadi, N.; Babaei, K.; Farsaraei, S.; Moghaddam, M.; Ghasemi Pirbalouti, A. Changes in essential oil compositions, total phenol, flavonoids and antioxidant capacity of Achillea millefolium at different growth stages. Ind. Crops Prod. 2020, 152, 112570. https://doi.org/10.1016/j.indcrop.2020.112570.

25.     Figueiredo, A.C.; Barroso, J.G.; Pais, M.S.S.; Scheffer, J.J.C. Composition of the essential oils from leaves and flowers of Achillea millefolium L. ssp. millefolium. Flavour Fragr. J. 1992, 7, 219–222. https://doi.org/10.1002/ffj.2730070409.

26.     Haziri, A.I.; Aliaga, N.; Ismaili, M.; Govori-odai, S.; Leci, O.; Faiku, F.; Arapi, V.; Haziri, I. Secondary metabolites in essential oil of Achillea millefolium (L.) growing wild in east part of Kosova. Am. J. Biochem. Biotechnol. 2010, 6, 32–34. https://doi.org/10.3844/ajbbsp.2010.32.34.

27.     Howyzeh, M.S.; Aslani, S.; Pooraskari, O. Essential oil profile of an Iranian yarrow (Achillea millefolium). J. Essent. Oil-Bear. Plants. 2019, 22, 295–300. https://doi.org/10.1080/0972060X.2019.1586589.

28.     Jaimand, K.; Rezaee, M.B.; Mozaffarian, V. Chemical constituents of the leaf and flower oils from Achillea millefolium ssp. elbursensis Hub.-Mor. from Iran rich in chamazulene. J. Essent. Oil Res. 2006, 18, 293–295, https://doi.org/10.1080/10412905.2006.9699093.

29.     Judzentiene, A.; Mockute, D. Essential oil composition of two yarrow taxonomic forms. Cent. Eur. J. Biol. 2010, 5, 346–352. https://doi.org/10.2478/s11535-010-0011-7.

30.     Kokkalou, E.; Kokkini, S.; Hanlidou, E. Volatile constituents of Achillea millefolium in relation to their infraspecific variation. Biochem. Syst. Ecol. 1992, 20, 665–670, doi:10.1016/0305-1978(92)90023-7.

31.     Azizi, M.; Chizzola, R.; Ghani, A.; Oroojalian, F. Composition at different development stages of the essential oil of four Achillea species grown in Iran. Nat. Prod. Commun. 2010, 5, 283–290, https://doi.org/10.1177/1934578x1000500224.

32.     Konarska, A.; Weryszko-Chmielewska, E.; Sulborska-Różycka, A.; Kiełtkya-Dadasiewicz, A.; Dmitruk, M.; Gorzel, M. Herb and flowers of Achillea millefolium subsp. millefolium L.: Structure and histochemistry of secretory tissues and phytochemistry of essential oils. Molecules. 2023, 28, 7791. https://doi.org/10.3390/molecules28237791.

33.     Nadim, M.M.; Malik, A.A.; Ahmad, J.; Bakshi, S.K. The essential oil composition of Achillea millefolium L. cultivated under tropical condition in India. World J. Agric. Sci. 2011, 7, 561–565.

34.     Nenaah, G.E. Chemical composition, toxicity and growth inhibitory activities of essential oils of three Achillea species and their nano-emulsions against Tribolium castaneum (Herbst). Ind. Crops Prod. 2014, 53, 252–260, https://doi.org/10.1016/j.indcrop.2013.12.042.

35.     Orav, A.; Kailas, T.; Ivask, K. Composition of the essential oil from Achillea millefolium L. from Estonia. J. Essent. Oil Res. 2001, 13, 290–294. https://doi.org/10.1080/10412905.2001.9699697.

36.     Orth, M.; Czygan, F.C.; Dedkov, V.P. Variation in essential oil composition and chiral monoterpenes of Achillea millefolium s.l. from Kaliningrad. J. Essent. Oil Res. 1999, 11, 681–687. https://doi.org/10.1080/10412905.1999.9711995.

37.     Pino, J.A.; Rosado, A.; Fuentes, V. Chemical composition of the leaf oil of Achillea millefolium L. grown in Cuba. J. Essent. Oil Res. 1998, 10, 427–428. https://doi.org/10.1080/10412905.1998.9700934.

38.     Rahimmalek, M.; Tabatabaei, B.E.S.; Etemadi, N.; Goli, S.A.H.; Arzani, A.; Zeinali, H. Essential oil variation among and within six Achillea species transferred from different ecological regions in Iran to the field conditions. Ind. Crops Prod. 2009, 29, 348–355. https://doi.org/10.1016/j.indcrop.2008.07.001.

39.     Rowshan, V.; Bahmanzadegan, A. Effects of salicylic acid on essential oil components in yarrow (Achillea millefolium Boiss). Int. J. Basic Sci. Appl. Res. 2013, 2, 347–351.

40.     Shawl, A.S.; Srivastava, S.K.; Syamasundar, K. V.; Tripathi, S.; Raina, V.K. Essential oil composition of Achillea millefolium L. growing wild in Kashmir, India. Flavour Fragr. J. 2002, 17, 165–168. https://doi.org/10.1002/ffj.1074.

41.     Smelcerovic, A.; Lamshoeft, M.; Radulovic, N.; Ilic, D.; Palic, R. LC-MS analysis of the essential oils of Achillea millefolium and Achillea crithmifolia. Chromatographia. 2010, 71, 113–116. 10.1365/s10337-009-1393-4.

42.     Ben Abdallah, S.; Riahi, C.; Vacas, S.; Navarro-Llopis, V.; Urbaneja, A.; Pérez-Hedo, M. The dual benefit of plant essential oils against Tuta absoluta. Plants. 2023, 12, 985. https://doi.org/10.3390/plants12050985.

43.     Stevanovic, Z.D.; Pljevljakušic, D.; Ristic, M.; Šoštaric, I.; Kresovic, M.; Simic, I.; Vrbnièanin, S. Essential oil composition of Achillea millefolium agg. populations collected from saline habitats in Serbia. J. Essent. Oil-Bear. Plants. 2015, 18, 1343–1352. https://doi.org/10.1080/0972060X.2014.884952.

44.     Suleimenov, Y.M.; Atazhanova, G.A.; Ozek, T.; Demirci, B.; Kulyyasov, A.T.; Adekenov, S.M.; Baser, K.H.C. Essential oil composition of three species of Achillea from Kazakhstan. Chem. Nat. Compd. 2001, 37, 447–450.

45.     Verma, R.S.; Joshi, N.; Padalia, R.C.; Goswami, P.; Singh, V.R.; Chauhan, A.; Verma, S.K.; Iqbal, H.; Verma, R.K.; Chanda, D.; Sundaresan, V.; Darokar, M.P. Chemical composition and allelopathic, antibacterial, antifungal and in vitro acetylcholinesterase inhibitory activities of yarrow (Achillea millefolium L.) native to India. Ind. Crops Prod. 2017, 104, 144–155. https://doi.org/10.1016/j.indcrop.2017.04.046.

46.     Mazandarani, M.; Mirdeilami, S.Z.; Pessarakli, M. Essential oil composition and antibacterial activity of Achillea millefolium L. from different regions in North east of Iran. J. Med. Plants Res. 2013, 7, 1063–1069. https://doi.org/10.5897/JMPR12.961.

47.     Bertoli, A.; Conti, B.; Mazzoni, V.; Meini, L.; Pistelli, L. Volatile chemical composition and bioactivity of six essential oils against the stored food insect Sitophilus zeamais Motsch. (Coleoptera Dryophthoridae). Nat. Prod. Res. 2012, 26, 2063–2071. https://doi.org/10.1080/14786419.2011.607453.

48.     Boskovic, Z.; Radulovic, N.; Stojanovic, G. Essential oil composition of four Achillea species from the Balkans and its chemotaxonomic significance. Chem. Nat. Compd. 2005, 41, 674–678. https://doi.org/10.1007/s10600-006-0009-6.

49.     Candan, F.; Unlu, M.; Tepe, B.; Daferera, D.; Polissiou, M.; Sökmen, A.; Akpulat, H.A. Antioxidant and antimicrobial activity of the essential oil and methanol extracts of Achillea millefolium subsp. millefolium Afan. (Asteraceae). J. Ethnopharmacol. 2003, 87, 215–220. https://doi.org/10.1016/S0378-8741(03)00149-1.

50.     Czerniewicz, P.; Chrzanowski, G.; Sprawka, I.; Sytykiewicz, H. Aphicidal activity of selected Asteraceae essential oils and their effect on enzyme activities of the green peach aphid, Myzus persicae (Sulzer). Pestic. Biochem. Physiol. 2018, 145, 84–92. https://doi.org/10.1016/j.pestbp.2018.01.010.

51.     Daniel, P.S.; Lourenço, E.L.B.; da Cruz, R.M.S.; De Souza Gonçalves, C.H.; Das Almas, L.R.M.; Hoscheid, J.; da Silva, C.; Jacomassi, E.; Brum Junior, L.; Alberton, O. Composition and antimicrobial activity of essential oil of yarrow (Achillea millefolium L.). Aust. J. Crop Sci. 2020, 14, 545–550. https://doi.org/10.21475/ajcs.20.14.03.p2325.

52.     de Sant’Anna, J.R.; da Silva Franco, C.C.; Miyamoto, C.T.; Cunico, M.M.; Miguel, O.G.; Côcco, L.C.; Yamamoto, C.I.; Corrêa Junior, C.; de Castro-Prado, M.A.A. Genotoxicity of Achillea millefolium essential oil in diploid cells of Aspergillus nidulans. Phyther. Res. 2008, 22, 544–549. https://doi.org/10.1002/ptr.2596.

53.     van den Dool, H.; Kratz, P.D. A generalization of the retention index system including linear temperature programmed gas-liquid partition chromatography. J. Chromatogr. A 1963, 11, 463–471. https://doi.org/10.1016/S0021-9673(01)80947-X.

54.     Adams, R.P. Identification of Essential Oil Components by Gas Chromatography/Mass Spectrometry; 4th ed.; Allured Publishing: Carol Stream, IL, USA, 2007; ISBN 978-1-932633-21-4.

55.     Mondello, L. FFNSC 3; Shimadzu Scientific Instruments: Columbia, Maryland, USA, 2016.

56.     NIST20; National Institute of Standards and Technology: Gaithersburg, Maryland, USA, 2020.

57.     Satyal, P. Development of GC-MS Database of Essential Oil Components by the Analysis of Natural Essential Oils and Synthetic Compounds and Discovery of Biologically Active Novel Chemotypes in Essential Oils, Ph.D. dissertation, University of Alabama in Huntsville, Huntsville, AL, USA, 2015.

58.     Farajpour, M.; Ebrahimi, M.; Baghizadeh, A.; Aalifar, M. Phytochemical and yield variation among Iranian Achillea millefolium accessions. Hort. Sci. 2017, 52, 827–830. https://doi.org/10.21273/HORTSCI11654-16.

59.     Poudel, A.; Satyal, P.; Swor, K.; Setzer, W.N. Essential oils of two Great Basin composites: Chaenactis douglasii and Dieteria canescens from southwestern Idaho. J. Essent. Oil Plant Comp. 2023, 1, 275–283. https://doi.org/10.58985/jeopc.2023.v01i03.35.

60.     Swor, K.; Satyal, P.; Poudel, A.; Setzer, W.N. Chemical characterization of three Artemisia tridentata essential oils and multivariate analyses: A preliminary investigation. Nat. Prod. Commun. 2023, 18, 1934578X231154965. https://doi.org/10.1177/1934578X231154965.

61.     Swor, K.; Satyal, P.; Poudel, A.; Setzer, W.N. The essential oil of Balsamorhiza sagittata from southwestern Idaho: Chemical composition and enantiomeric distribution. Nat. Prod. Commun. 2024, 19, 1934578X231225842. https://doi.org/10.1177/1934578X231225842.

62.     Swor, K.; Satyal, P.; Poudel, A.; Setzer, W.N. The essential oils of Wyethia species: Wyethia amplexicaulis (Nutt.) Nutt. and Wyethia helianthoides Nutt. Nat. Prod. Commun. 2024, 19, 1934578X241248081. https://doi.org/10.1177/1934578X241248081.

63.     de Sousa, D.P. Analgesic-like activity of essential oils constituents. Molecules 2011, 16, 2233–2252. https://doi.org/10.3390/molecules16032233.

64.     Craven, R. The comfort of camphor. Nat. Rev. Neurosci. 2005, 6, 826. https://doi.org/10.1038/nrn1801.

65.     Laude, E.A.; Morice, A.H.; Grattan, T.J. The antitussive effects of menthol, camphor and cineole in conscious Guinea-pigs. Pulm. Pharmacol. 1994, 7, 179–184. https://doi.org/10.1006/pulp.1994.1021.

66.     Viljoen, A.; Van Vuuren, S.; Ernst, E.; Klepser, M.; Demirci, B.; Başer, H.; Van Wyk, B.E. Osmitopsis asteriscoides (Asteraceae)-the antimicrobial activity and essential oil composition of a Cape-Dutch remedy. J. Ethnopharmacol. 2003, 88, 137–143. https://doi.org/10.1016/S0378-8741(03)00191-0.

67.     Johansen, B.; Duval, R.E.; Sergere, J.C. First evidence of a combination of terpinen-4-ol and α-terpineol as a promising tool against ESKAPE pathogens. Molecules. 2022, 27, 7472. https://doi.org/10.3390/molecules27217472.

68.     Pongprayoon, U.; Soontornsaratune, P.; Jarikasem, S.; Sematong, T.; Wasuwat, S.; Claeson, P. Topical antiinflammatory activity of the major lipophilic constituents of the rhizome of Zingiber cassumunar. Part I: The essential oil. Phytomed. 1997, 3, 319.322. https://doi.org/10.1016/S0944-7113(97)80003-7.

69.     Hart, P.H.; Brand, C.; Carson, C.F.; Riley, T. V.; Prager, R.H.; Finlay-Jones, J.J. Terpinen-4-ol, the main component of the essential oil of Melaleuca alternifolia (tea tree oil), suppresses inflammatory mediator production by activated human monocytes. Inflamm. Res. 2000, 49, 619–626. https://doi.org/10.1007/s000110050639.

70.     Nogueira, M.N.M.; Aquino, S.G.; Rossa, C.; Spolidorio, D.M.P. Terpinen-4-ol and alpha-terpineol (tea tree oil components) inhibit the production of IL-1β, IL-6 and IL-10 on human macrophages. Inflamm. Res. 2014, 63, 769–778. https://doi.org/10.1007/s00011-014-0749-x.

71.     Fonsêca, D. V.; Salgado, P.R.R.; de Carvalho, F.L.; Salvadori, M.G.S.S.; Penha, A.R.S.; Leite, F.C.; Borges, C.J.S.; Piuvezam, M.R.; Pordeus, L.C. de M.; Sousa, D.P.; Almeida, R.N.. Nerolidol exhibits antinociceptive and anti-inflammatory activity: Involvement of the GABAergic system and proinflammatory cytokines. Fundam. Clin. Pharmacol. 2016, 30, 14–22. https://doi.org/10.1111/fcp.12166.