Skip to main content
NCBI home page
Molecules logoLink to Molecules
. 2023 Jan 23;28(3):1131. doi: 10.3390/molecules28031131

Multivariate Analysis of Essential Oil Composition of Artemisia annua L. Collected from Different Locations in Korea

Minji Hong 1, Minju Kim 1, Haejung Jang 1, Sela Bo 1, Ponnuvel Deepa 1, Kandhasamy Sowndhararajan 2, Songmun Kim 1,*
Editor: Manuela Labbozzetta
PMCID: PMC9920137  PMID: 36770797

Abstract

Artemisia annua L. is distributed throughout the world and it is an important medicinal plant in Korea to treat various human diseases. Recently, A. annua has also been considered to be an effective ethnobotanical drug against COVID-19. A. annua contains an appreciable amount of essential oil with different biological properties. However, the composition of essential oils in aromatic plants can be varied depending on several factors, including geographic, genetic, ecological, etc. Hence, the present study aimed to investigate the chemical diversity of essential oils of Korean A. annua collected from different locations in Korea by multivariate analysis. For this purpose, the seeds of A. annua were collected from 112 different locations in Korea and were grown under the same environmental conditions. Except for nine individuals which decayed during the cultivation, essential oils were isolated from the aerial parts of 103 A. annua individuals (AEOs) using the steam distillation extraction method, and their chemical compositions were determined by GC-MS analysis. Furthermore, a multivariate analysis was performed to distinguish the difference between 103 individuals of A. annua based on their essential oil compositions. The yield of A. annua essential oils ranged from 0.04 to 1.09% (v/w). Based on the GC-MS data, A. annua individuals were grouped into six chemotypes such as artemisia ketone, camphor, β-cubebene, eucalyptol, α-pinene, and β-selinene. The multivariate analysis results revealed that Korean A. annua could be largely grouped into three clusters such as artemisia ketone, eucalyptol, and β-selinene. Among 35 components selected for principal component analysis (PCA), PC1, PC2, and PC3 accounted for 82.55%, 8.74%, and 3.62%, respectively. Although all individuals of A. annua were cultivated under the same environmental conditions, there is an intraspecific chemical diversity that exists within Korean native species.

Keywords: Artemisia annua, chemotype, essential oil, Gae-ddong-ssuk, multivariate analysis

1. Introduction

The genus Artemisia belongs to the family of Asteraceae (Compositae) and it comprises about 500 species [1]. Among them, Artemisia annua L. (sweet wormwood or sweet sagewort) is wildly distributed in Asian countries, mainly in China, Japan, and Korea, and it is now naturalized in North American and European countries [2,3,4]. The Korean name of A. annua is Gae-ddong-ssuk, which means smell like dog’s excretion when the leaves were rubbed [5]. In Korea, A. annua has been used in traditional systems of medicine for hundreds of years [6]. A. annua is widely known for its effective anti-malarial component, artemisinin (a sesquiterpene lactone) [7]. Recently, A. annua has been in the limelight as an effective ethnobotanical drug against COVID-19 [8]. Previous studies showed that 100 types of chemical components were identified from A. annua [9].

In the past few decades, many studies reported that A. annua essential oil (AEO) has a variety of biological properties, including antimicrobial, anticancer, anti-inflammatory, antinociceptive, anti-obesity, antioxidant, antipyretic, etc. Further studies reported on the utilization of AEO in aromatherapy, cosmetics, fragrances, groceries, and pharmaceutics [3,7,10,11,12]. The essential oils of A. annua are mainly comprised of monoterpenoids and sesquiterpenes. However, the profile of essential oils exhibited great variations in the three major components, artemisia ketone, 1,8-cineole, and camphor, depending on the geographical origin of the plant [2,13,14]. Zhang et al. [9] also reported variations in the main secondary metabolites of A. annua such as arteannuin B, artemisinin, artemisinic acid, and scopoletin, according to different geographical locations in China.

Plants within the same species exhibit some morphological differences. However, the variability in the chemical composition of essential oils has been reported, depending on various factors such as geographical origins, cultivation conditions, stage of maturity, harvesting season, genotype, etc. [2,12,13]. AEOs collected from different geographical regions showed markedly different compositions. For instance, artemisia ketone was the major component in Chinese, French, and Indian AEOs. In the case of Iranian AEO, camphor (48.0%) was the most abundant component but showed variations in its concentration (2.8–64%). The essential oils isolated from North American A. annua that exhibited artemisia ketone (35.7–68.0%) and eucalyptol (22.8–31.5%) were major components with different proportions [2]. In Tajikistan, A. annua samples collected from three different locations exhibited camphor (32.5–58.9%) camphene (4.5–8.4%), eucalyptol (13.7–17.8%), and α-pinene (1.9–7.3%) as major components [3]. Therefore, it is important to understand the chemical composition of essential oils of A. annua collected from different geographical regions. Multivariate analysis is an important statistical analysis method to determine and classify the chemical or morphological characteristics of plant species by cluster analysis and principal component analysis [15,16,17]. Previously, Radulović et al. [18] grouped AEOs into four classes based on multivariate analysis. In another study, essential oils from A. annua of different origins cultivated in Finland were divided into four classes according to cluster analysis [19]. Hence, the multivariate analysis offers insight into the distribution of essential oil components in plant populations.

It is well understood that the chemical components of AEOs vary significantly based on geographical location. There is no study about variations in the chemical composition of essential oils within Korean populations of A. annua. Hence, the present study aimed to demonstrate the variation in the chemical composition of essential oils from Korean A. annua individuals. To do this, we collected seeds of A. annua from different sites in Korea and cultivated the plants under the same environmental conditions, and analyzed AEOs, using gas chromatography and mass spectrometry analysis (GC-MS). Finally, we performed a multivariate analysis based on the chemical profile of AEOs to classify chemotypes and identify the chemical diversity of A. annua individuals in Korea.

2. Results and Discussion

2.1. Yield and Color of Korean A. annua Essential Oils

A. annua is one of the most useful aromatic plants found around the world. Many researchers reported that AEO components, such as mono-/sesqui-terpenoids, and other phenolic-derived aromatic compounds have been used in several fields such as food, fragrance, and cosmetics. Essential oils possess a wide range of biological properties owing to the presence of a variety of specialized metabolites [12,20]. Furthermore, A. annua is the only recognized source of an effective anti-malarial compound, artemisinin [21]. In this study, 112 A. annua seeds were collected from diverse sites in Korea and cultivated in the field under the same environmental conditions. Of these, nine seedlings decayed during the cultivation. The yield and the color of essential oils from the aerial parts of A. annua were diverse according to the sampling sites, and the yield (v/w) ranged from 0.04 to 1.09%. The color of AEOs was classified into pale yellow, yellow, and dark yellow (Figure 1), but was most commonly pale yellow in color. Table 1 shows the extraction yield and color of essential oils from A. annua individuals.

Figure 1.

Figure 1

Open in a new tab

The color classification of A. annua essential oils. (a) pale yellow; (b) yellow; (c) dark yellow.

Table 1.

The yield (v/w %) and color of essential oils from Korean A. annua individuals.

No. Samples Yield (%) Color No. Samples Yield (%) Color No. Samples Yield (%) Color
1 AA1 0.237 Y 36 AA40 0.288 DY 71 AA78 0.689 DY
2 AA2 0.527 DY 37 AA41 0.046 Y 72 AA80 0.645 PY
3 AA3 0.142 DY 38 AA42 0.107 DY 73 AA82 0.697 PY
4 AA4 0.311 Y 39 AA43 0.076 DY 74 AA83 0.664 Y
5 AA5 0.723 PY 40 AA44 0.038 PY 75 AA84 0.647 PY
6 AA6 0.227 DY 41 AA45 0.038 Y 76 AA85 0.617 Y
7 AA7 0.088 DY 42 AA46 0.041 DY 77 AA86 0.500 DY
8 AA11 0.360 Y 43 AA47 0.060 Y 78 AA87 0.745 Y
9 AA12 0.377 DY 44 AA48 0.058 DY 79 AA88 0.690 PY
10 AA13 0.223 DY 45 AA49 0.059 Y 80 AA89 0.561 PY
11 AA14 0.440 PY 46 AA50 0.039 DY 81 AA90 0.932 PY
12 AA15 0.335 Y 47 AA51 0.064 Y 82 AA91 1.088 PY
13 AA16 0.330 PY 48 AA52 0.037 DY 83 AA92 0.629 PY
14 AA17 0.435 Y 49 AA53 0.049 Y 84 AA93 0.792 PY
15 AA18 0.273 DY 50 AA54 0.063 DY 85 AA94 0.895 PY
16 AA20 0.194 DY 51 AA55 0.085 DY 86 AA95 0.983 PY
17 AA21 0.367 DY 52 AA56 0.041 PY 87 AA96 1.063 PY
18 AA22 0.257 DY 53 AA57 0.059 PY 88 AA97 1.060 PY
19 AA23 0.426 Y 54 AA58 0.050 PY 89 AA98 0.818 PY
20 AA24 0.490 DY 55 AA59 0.061 Y 90 AA99 0.751 PY
21 AA25 0.533 Y 56 AA60 0.046 PY 91 AA100 0.744 PY
22 AA26 0.492 DY 57 AA61 0.630 Y 92 AA101 0.767 PY
23 AA27 0.305 DY 58 AA62 0.720 PY 93 AA102 0.913 PY
24 AA28 0.526 DY 59 AA63 0.772 PY 94 AA103 0.798 PY
25 AA29 0.519 Y 60 AA64 0.827 PY 95 AA104 0.762 PY
26 AA30 0.213 Y 61 AA65 0.624 PY 96 AA105 0.574 PY
27 AA31 0.369 Y 62 AA66 0.581 PY 97 AA106 0.771 PY
28 AA32 0.137 DY 63 AA67 0.652 PY 98 AA107 0.903 PY
29 AA33 0.380 Y 64 AA68 0.566 Y 99 AA108 0.561 PY
30 AA34 0.355 Y 65 AA69 0.606 PY 100 AA109 0.663 PY
31 AA35 0.311 DY 66 AA70 0.624 PY 101 AA110 0.566 PY
32 AA36 0.267 DY 67 AA71 0.650 PY 102 AA111 0.536 PY
33 AA37 0.214 DY 68 AA72 0.891 PY 103 AA112 0.926 PY
34 AA38 0.361 DY 69 AA74 0.501 Y
35 AA39 0.337 Y 70 AA75 0.910 PY
Open in a new tab

Color–DY: dark yellow; PY: pale yellow; Y: yellow.

Previous studies reported that the yield of essential oils from A. annua significantly varied according to the geographical origin of the plants and their plant parts used for the extraction. Holm et al. [19] reported that the extraction yield from the leaves of AEOs collected in four different countries such as China, Hungary, Italy, and Yugoslavia ranged between 0.4 and 0.9%. In Jwarharti, the yield of AEOs from leaves, petals, and stems collected during the flowering season were 1.5%, 1.8%, and 0.2%, respectively [22]. In Russia, the recovery rate and color of AEOs were also different according to the extraction parts. The yield was 0.7% from the aerial parts and 2.0% from the leaves and inflorescence parts. The color of the oils was yellow to green-yellow [17]. The yield of AEO from the aerial parts collected in Serbia was 0.16% [23]. In Korea, Shin [24] reported that the average yield of essential oil from the dried aerial parts of wild A. annua was 0.11%. Bhakuni et al. [25] and Bilia et al. [2] demonstrated that the yield of AEOs was generally between 0.3 and 0.4% (v/w), but could be as high as 4.0% depending on harvesting time, genotypes, and geographic conditions.

2.2. Chemical Variations of Korean A. annua Essential Oils

The GC-MS data demonstrated that 103 individuals of Korean A. annua were classified into 6 chemotypes according to the predominant components in each essential oil (Table 2). A total of 178 chemical constituents were identified in 103 individuals of AEOs based on the RI value and mass spectral data. Among them, the most dominant chemotype was artemisia ketone (75 individuals), followed by β-selinene (17 individuals), β-cubebene (five individuals), eucalyptol (four individuals), camphor (one individual), and α-pinene (one individual) chemotypes. Furthermore, Figure 2 shows chromatograms of representative major components chosen for six chemotypes of A. annua. It was observed that the content of monoterpenoids was higher than the sesquiterpenoids in most of the AEOs. The essential oils of Korean A. annua individuals markedly differed both qualitatively and quantitatively.

Table 2.

The chemotype classification of Korean A. annua individuals based on the major component of essential oils.

Chemotypes Content Ratio (%) Samples
Artemisia ketone
(75)		 20.51–83.82 AA1, AA2, AA4, AA5, AA6, AA11, AA12, AA13, AA14, AA15, AA16, AA17, AA20, AA21 AA22, AA24, AA25, AA26, AA27, AA28, AA32, AA33, AA34, AA35, AA36, AA37, AA38, AA39, AA40, AA61, AA62, AA63, AA64, AA65, AA66, AA67, AA68, AA69, AA70, AA71, AA72, AA74, AA75, AA78, AA80, AA82, AA83, AA85, AA86, AA87, AA88, AA89, AA90, AA91, AA92, AA93, AA94, AA95, AA96, AA97, AA98, AA99, AA100, AA101, AA102, AA103, AA104, AA105, AA106, AA107, AA108, AA109, AA110, AA111, AA112
Camphor
(1)		 25.05 AA30
β-Cubebene
(5)		 13.90–22.52 AA47, AA48, AA51, AA55, AA57
Eucalyptol
(4)		 15.07–43.01 AA23, AA29, AA31, AA84
α-Pinene
(1)		 21.16 AA18
β-Selinene
(17)		 20.05–46.29 AA3, AA7, AA41, AA42, AA43, AA44, AA45, AA46, AA49, AA50, AA52, AA53, AA54, AA56, AA58, AA59, AA60
Open in a new tab

The numbers in the parenthesis denote the total number of samples respective to each chemotype.

Figure 2.

Figure 2

Open in a new tab

The GC-MS chromatograms of six representative chemotypes of Korean A. annua individuals. The peak of major components was marked with a green arrow: (A) artemisia ketone; (B) camphor; (C) β-cubebene; (D) eucalyptol; (E) α-pinene; (F) β-selinene. The sample names of respective chromatograms: AA11, Hongcheon; AA30, Pyeongtaek; AA55, Gwangju; AA23, Chuncheon; AA18, Danyang; AA49, Sejong.

Similar to the present study, previous studies revealed that artemisia ketone, camphor, caryophyllene, eucalyptol, and α-pinene are the major compounds of AEOs [2,13,26]. Hwang et al. [14] identified 34 compounds in Korean AEO, and the major compounds were eucalyptol (20.6%), germacrene D (19.3%), and caryophyllene (11.4%). On the other hand, Shin [24] reported that among the 85 chemicals contained in Korean AEO, caryophyllene oxide (11.7%), caryophyllene (7.5%), camphor (7.3%), 1,8-cineole (5.0%), and borneol (4.0%) were principal components. Bilia et al. [2] grouped AEOs (aerial parts) in accordance with the major compound and its content as Chinese (artemisia ketone, 64.0%), French (artemisia ketone, 2.8–55.0%; eucalyptol, 1.2–11.6%; germacrene D, 15.0%), Indian (artemisia ketone, 11.5–58.8%), Iranian (camphor, 48.0%; eucalyptol, 9.4%), North American (artemisia ketone, 35.7–68.0%; eucalyptol, 22.8–31.5%), and Vietnamese (camphor, 3.3–21.8%; germacrene D, 0.3–18.9%). In a recent study, Liu et al. [27] found that the most abundant components of AEO collected in China were artemisia ketone (70.6%), α-caryophyllene (5.1%), and germacrene D (3.8%).

However, Tzenkova et al. [28] reported that Bulgarian AEO obtained from the aerial parts mainly contained sesquiterpenoids (67.4%), followed by monoterpenoids (18.0%), and the most abundant component was α-caryophyllene (24.7%). A recent study reported that the major constituents of AEOs collected from three different locations in Tajikistan were camphor (32.5–58.9%), camphene (4.5–8.4%), eucalyptol (13.7–17.8%), and α-pinene (1.9–7.3%) [3]. Another study found that the essential oils obtained from five Artemisia species including A. annua were dominated by either monoterpenes or sesquiterpenes according to the species and their geographical origin. The most abundant components identified in the essential oils of five Artemisia species were β-pinene, chamazulene, germacrene D, camphor, pinocarvone, and thuja-2,4(10)-diene [23].

In the case of AEO from the root part, cis-arteannuic alcohol (25.9%) was the major component [22]. The most abundant component in the Romanian AEO was camphor (17.74%), followed by α-pinene, germacrene D, 1,8-cineole, trans-β-caryophyllene, and artemisia ketone [29]. In the case of AEO from Tuscany, the major components were camphor (25.2%), 1,8-cineole (20%), and artemisia ketone (12.5%) [30]. It was reported that the flowering top of AEO contained a higher amount of camphor (22.6%), followed by artemisia ketone (17.3%) and 1,8-cineole (15.8%) [31]. These studies clearly indicated the variations in the AEOs according to their geographical origin. In contrast to many other studies, this study could identify the chemotypes of sesquiterpenoids, either β-cubebene or β-selinene, from Korean A. annua. It is well known that the essential oil composition can change from plant to plant within the same species. In general, various abiotic and biotic factors in addition to postharvest treatments affect the plant’s secondary metabolite production [32].

The major component, especially artemisia ketone, is an irregular monoterpene with green herbaceous fragrance, used in the perfume and cosmetic industries [33]. Camphor has also been extensively used as a fragrance and food flavorant. It is used for the treatment of minor muscle pains and as a skin penetration enhancer. Camphor possesses several biological properties such as insecticidal, antimicrobial, anti-nociceptive, and anticancer activities [34,35]. Another major component, eucalyptol (1,8-cineole), showed anti-inflammatory and antioxidant properties. In addition, eucalyptol is used for the treatment of respiratory and cardiovascular diseases [36]. α-Pinene is one of the most important monoterpenes used in the fragrance and flavor industry and has been used for the treatment of respiratory tract infections for several decades. α-Pinene has antibacterial, insecticidal, antioxidant, and anti-cancer properties [37]. β-cubebene and β-Selinene are also important sesquiterpene hydrocarbons in AEOs.

2.3. Multivariate Analysis

Multivariate analysis is one of the extensively used techniques to describe possible relationships between essential oils and their chemical compositions [38]. Out of 178 essential oil components, 35 components that appeared in over 50 individuals of A. annua were selected for multivariate analysis (Supplementary Table S1). Artemisia ketone, artemisia alcohol, camphor, caryophyllene, caryophyllene oxide, and α-pinene were reported as the major components of AEOs [3,12,19]. In this study, these components were also included in 35 common chemicals.

2.3.1. Cluster Analysis

Figure 3 indicates a dendrogram of Korean A. annua individuals based on their essential oil components. The result of cluster analysis demonstrated that Korean A. annua individuals could be classified into three major groups. In the group I, A. annua individuals which have the highest content of artemisia ketone with a ratio of monoterpenoids content of over 64% were included. Individuals of A. annua with a higher amount of sesquiterpenoids such as β-selinene were placed under Group II. Group III consisted of A. annua individuals with a similar proportion of mono-/sesqui-terpenoid contents. In Table 3, the chemical characteristics of individuals of Korean A. annua were summarized according to different groups.

Figure 3.

Figure 3

Open in a new tab

Dendrogram shows three groups of 103 A. annua individuals based on their essential oil components.

Table 3.

Characteristics of chemical composition for three different clusters of A. annua individuals from Korea.

Group Major Compound Chemical Characteristics
I Artemisia ketone Monoterpenoids content ratio in the essential oil is dominant (monoterpenoids content ratio > 64%; artemisia ketone ratio > 41%).
II β-Selinene Sesquiterpenoids content ratio in the essential oil is dominant(sesquiterpenoids content ratio > 37%; β-selinene > 20%)
III Eucalyptol, β-cubebene Monoterpenoids and sesquiterpenoids content ratio in the essential oil is similar (monoterpenoids content:sesquiterpenoids content = 1:1)
Open in a new tab

Previous studies also compared and analyzed A. annua individuals based on the composition of major essential oil components. Radulović et al. [18] reported that AEOs could be categorized into four classes (Class 1: camphor and camphor/eucalyptol; Class 2: artemisia ketone/eucalyptol/α-pinene and artemisia ketone/camphor/eucalyptol; Class 3: artemisia ketone/camphor/germacrene D; and Class 4: β-caryophyllene/germacrene D and artemisia ketone/β-caryophyllene/eucalyptol/germacrene D). Sharopov et al. [3] also suggested that AEOs were classified into three types, such as group–I camphor/eucalyptol, group II–camphor, and group III–artemisia ketone. Based on a PCA of essential oils, five Artemisia species including A. arborescens, A. campestris, A. lobelii, A. annua, and A. absinthium were separated into camphor, chamazulene and α-pinene [23]. Holm et al. [19] divided seven batches of A. annua, which were native to different countries, into four clusters according to their essential oil compositions, and it was found that the genotype was strongly correlated with the chemical compositions. Charles et al. [26] also reported that the great diversity in AEOs’ constituents was based upon genetic differences, and suggested that the determination of the essential oil composition is important for improving its quality.

2.3.2. Principal Component Analysis (PCA)

PCA eases the raw data’s complexity, but retains most of the information to highlight the variation [39]. As a result of PCA, 35 principal components (PCs) were sorted into three PCs. PC1, PC2, and PC3 occupied 82.55%, 8.74%, and 3.62% of the proportion of variance (Table 4), respectively. The cumulative proportion (%) of PC1 and PC2 accounted for 91.28%. Thus, PC1 and PC2 can be determined as the main principal components, and these were described intensively in this section. Table 4 shows the correlation coefficient between 35 common chemicals of A. annua and each principal component. PC1 is positively correlated with the contents of β-caryophyllene (C24; 0.716), β-selinene (C28; 0.708), β-cubebene (C23; 0.687), and α-muurolol (C33; 0.673), whereas it showed a high negative correlation with the contents of artemisia ketone (C10; −0.998) and artemisia alcohol (C12; −0.619). PC2 showed a high positive correlation with the contents of α-terpineol (C18; 0.810), eucalyptol (C9; 0.807), terpinene-4-ol (C17; 0.774), and α-terpinene (C6; 0.771). The chemicals which have a high correlation with PC1 and PC2 were summarized in Table 5. Moreover, Figure 4 shows a loading plot for the correlation of 35 common chemicals in AEOs with PC1 (x-axis) and PC2 (y-axis).

Table 4.

Principal component scores of 35 common chemicals in the essential oils of Korean A. annua individuals.

No. Chemical Name Code Principal Components
PC1 PC2 PC3
1 Santolina triene C1 −0.540 0.092 −0.066
2 α-Pinene C2 0.249 0.408 0.088
3 Camphene C3 0.303 0.526 0.085
4 β-Pinene C4 0.174 0.654 0.054
5 Yomogi alcohol C5 −0.516 0.148 0.126
6 α-Terpinene C6 0.264 0.771 −0.115
7 p-Cymene C7 0.403 0.315 0.186
8 Limonene C8 0.269 0.569 −0.185
9 Eucalyptol C9 0.113 0.807 −0.523
10 Artemisia ketone C10 −0.998 −0.063 −0.026
11 Sabinene hydrate C11 0.057 0.446 −0.291
12 Artemisia alcohol C12 −0.619 0.105 0.027
13 3-Isopentenyl isovalerate C13 −0.288 0.133 −0.094
14 Pinocarveol C14 0.245 0.382 0.093
15 Camphor C15 0.325 0.395 0.028
16 Pinocarvone C16 0.148 0.326 0.089
17 Terpinen-4-ol C17 0.361 0.774 −0.110
18 α-Terpineol C18 0.161 0.810 −0.401
19 3-Hexenyl isovalerate C19 −0.167 0.265 −0.168
20 α-Longipinene C20 −0.019 −0.046 −0.293
21 α-Copaene C21 0.267 0.010 0.229
22 Benzyl isovalerate C22 0.641 −0.371 −0.006
23 β-Cubebene C23 0.687 −0.262 0.442
24 β-Caryophyllene C24 0.716 −0.245 0.275
25 β-Farnesene C25 −0.418 0.279 −0.064
26 α-Humulene C26 0.292 0.048 0.189
27 β-Chamigrene C27 −0.241 0.199 0.010
28 β-Selinene C28 0.708 −0.598 −0.371
29 γ-Elemene C29 0.647 −0.093 0.411
30 Butylated hydroxytoluene C30 −0.243 0.038 0.136
31 δ-Cadinene C31 0.670 −0.221 0.188
32 Caryophyllene oxide C32 0.469 −0.193 0.261
33 α-Muurolol C33 0.673 −0.380 0.311
34 Vulgarone B C34 −0.331 0.160 −0.144
35 Lanceol C35 0.611 −0.313 0.399
Proportion of variance (%) 82.554 8.738 3.616
Cumulative proportion (%) 82.554 91.283 94.899
Open in a new tab

Extraction methods: Principal component analysis; three components were extracted. Bold letters–correlation coefficient was > 0.67 or < −0.61.

Table 5.

Correlation of common chemicals from A. annua essential oils with each principal component (PC1 and PC2).

PC Correlation Relevant Chemicals
PC1 Positive (+) β-Caryophyllene, β-selinene, β-cubebene, α-muurolol
Negative (−) Artemisia ketone, artemisia alcohol
PC2 Positive (+) α-Terpineol, eucalyptol, terpinene-4-ol, α-terpinene
Open in a new tab
Figure 4.

Figure 4

Open in a new tab

The loading plot of PCA shows the correlations between 35 common chemicals and principal components. Chemicals in green circle: Cr1 had a high correlation with PC1 (negative: artemisia ketone (C10); Cr2 had a high correlation with PC2 (positive: α-terpinene (C6); eucalyptol (C9); terpinen-4-ol (C17); α-terpineol (C18); Cr3 had a high correlation with PC1 (positive: β-cubebene (C23); β-caryophyllene (C24); β-selinene (C28); α-muurolol (C33)).

Using the PCA scores (PC1 and PC2), a scatter plot of Korean native A. annua individuals was constructed as shown in Figure 5. Based on 35 principal components, all individuals of A. annua could be largely classified into three groups, artemisia ketone, eucalyptol, and β-selinene. A. annua individuals, which have a high positive correlation with PC1 (high contents of β-selinene, β-caryophyllene, and β-cubebene or low content of artemisia ketone) were composed of AA7, AA41, AA42, AA43, AA44, AA45, AA46, AA49, AA50, AA52, AA53, AA54, AA56, AA58, AA59, and AA60. A total of 12 A. annua individuals such as AA15, AA18, AA23, AA24, AA29, AA30, AA31, AA64, AA66, AA71, AA84, and AA85 were correlated with PC2 (high contents of eucalyptol and α-terpineol). Zhigzhitzhapova et al. [17] reported that AEOs could be divided conditionally into two groups (Asian and European) based on PCA using their chemical composition data available in the literature.

Figure 5.

Figure 5

Open in a new tab

The scatter plot of PCA shows A. annua individuals’ relativeness based on 35 common chemicals: green circles indicate three major groups of the A. annua individuals: artemisia ketone, eucalyptol, and β-selinene groups.

2.3.3. Correlation Analysis

A correlation coefficient table showed the correlation between 35 common chemicals in Korean AEOs individuals (Supplementary Table S2). The results of correlation analysis indicated that all chemicals exhibited a complicate correlation between them. Therefore, chemicals that showed statistical significance at the 1% level and had a correlation value over 0.7 were explained in this section.

α-Pinene showed a high correlation with pinocarveol (0.890 **) and pinocarvone (0.797 **), camphene with β-pinene (0.831 **) and camphor (0.936 **), and β-pinene with limonene (0.706 **) and camphor (0.749 **). Yomogi alcohol had a high positive correlation with artemisia alcohol (0.802 **), α-terpinene with terpinene-4-ol (0.916 **) and α-terpineol (0.729 **), and α-terpineol with eucalyptol (0.874 **) and terpinene-4-ol (0.746 **). In addition, l-pinocarveol was highly correlated with pinocarvone (0.879 **), β-cubebene with β-caryophyllene (0.788 **) and γ-elemene (0.800 **), and α-muurolol with benzyl isovalerate (0.713 **) and lanceol (0.860 **). However, there is a strong negative correlation between artemisia ketone and β-caryophyllene (−0.703 **). Other chemicals showed a low correlation with each other, and these results would contribute to understanding the relationship between Korean A. annua individuals and their common chemicals (Supplementary Table S2).

In the multivariate analysis, the result of cluster analysis revealed the classification of 103 Korean A. annua individuals into three major groups based on the ratio of monoterpene and sesquiterpene compounds. In PCA, the selected 35 components were sorted into three PCs and the cumulative proportion of PC1 and PC2 accounted for 91.28%. Furthermore, Korean populations of A. annua were broadly classified into three groups such as artemisia ketone, eucalyptol, and β-selinene according to the PCA scatter plot.

The data of this study indicated that there were significant differences in the chemical components and their ratios of essential oils of 103 A. annua individuals collected from different regions in Korea. Attention should be paid to the variations in the chemical compositions within species, and differences in their biological properties need to be further investigated.

3. Materials and Methods

3.1. Collection and Cultivation of Korean A. annua Seeds

In this study, the seeds of 112 individuals of A. annua were collected from different locations in Korea during 2019–2021 and the collection was done with the support of Dr. Jang (Ph. D. of Botany in KNU) (Table 6). The collected seeds were stored at 4 °C and were sown in black seedling trays (128 holes, 17 cm3, Seoul-Bio, Korea) filled with horticultural media in April 2022. Every seedling tray was kept for 35–36 days in a glassed greenhouse at the Gangwon-do Agricultural Research and Extension Services (GARES) with constant temperature (23–25 °C) and humidity (50%). In early May, all seedlings of A. annua which reached a 3.5 leaf base were planted at the cultivation fields located in Chuncheon, Gangwon-do, Korea (N 37°55′45.4″; E 127°43′44.2″) (Figure 6). Except for the nine dead individuals that decayed during cultivation, 103 A. annua individuals were grown until the flowering stage and were harvested for the extraction of essential oils.

Table 6.

Collection sites of A. annua seeds from different places in Korea.

No. Sample Code Sampling Site No. Sample Code Sampling Site No. Sample Code Sampling Site
1 AA1 Wonju 39 AA39 Ulsan 77 AA77 Yanggu
2 AA2 Hwacheon 40 AA40 Bonghwa 78 AA78 Yanggu
3 AA3 Chuncheon 41 AA41 Imsil 79 AA79 Yanggu
4 AA4 Yangyang 42 AA42 Imsil 80 AA80 Yanggu
5 AA5 Sokcho 43 AA43 Jeonju 81 AA81 Yanggu
6 AA6 Goseong 44 AA44 Nonsan 82 AA82 Yanggu
7 AA7 Inje 45 AA45 Daejeon 83 AA83 Seoul
8 AA8 Yanggu 46 AA46 Hanam 84 AA84 Seoul
9 AA9 Yangpyeong 47 AA47 Pyeongtaek 85 AA85 Sungnam
10 AA10 Jeongseon 48 AA48 Sejong 86 AA86 Sungnam
11 AA11 Hongcheon 49 AA49 Sejong 87 AA87 Incheon
12 AA12 Hoengseong 50 AA50 Hanam 88 AA88 Incheon
13 AA13 Pyeongchang 51 AA51 Ulsan 89 AA89 Incheon
14 AA14 Namyangju 52 AA52 Ulsan 90 AA90 Daejeon
15 AA15 Pocheon 53 AA53 Bonghwa 91 AA91 Yeongcheon
16 AA16 Gapyeong 54 AA54 Bonghwa 92 AA92 Mungyeong
17 AA17 Chungju 55 AA55 Gwangju 93 AA93 Bonghwa
18 AA18 Danyang 56 AA56 Yongin 94 AA94 Gimcheon
19 AA19 Jecheon 57 AA57 Hongcheon 95 AA95 Bonghwa
20 AA20 Yeongwol 58 AA58 Seoul 96 AA96 Yeongju
21 AA21 Hongcheon 59 AA59 Seoul 97 AA97 Ulsan
22 AA22 Hongcheon 60 AA60 Samcheok 98 AA98 Ulsan
23 AA23 Chuncheon 61 AA61 Seoul 99 AA99 Ulsan
24 AA24 Chuncheon 62 AA62 Seoul 100 AA100 Ulsan
25 AA25 Hwacheon 63 AA63 Seoul 101 AA101 Changwon
26 AA26 Hwacheon 64 AA64 Seoul 102 AA102 Changwon
27 AA27 Chuncheon 65 AA65 Seoul 103 AA103 Changnyeong
28 AA28 Chuncheon 66 AA66 Seoul 104 AA104 Sacheon
29 AA29 Hongcheon 67 AA67 Seoul 105 AA105 Guri
30 AA30 Pyeongtaek 68 AA68 Anyang 106 AA106 Gapyeong
31 AA31 Yongin 69 AA69 Goyang 107 AA107 Ganghwa
32 AA32 Wonju 70 AA70 Nonsan 108 AA108 Paju
33 AA33 Incheon 71 AA71 Yeoju 109 AA109 Inje
34 AA34 Anyang 72 AA72 Yeoju 110 AA110 Ansan
35 AA35 Seoul 73 AA73 Yanggu 111 AA111 Yongin
36 AA36 Changwon 74 AA74 Yanggu 112 AA112 Chulwon
37 AA37 Ulsan 75 AA75 Yanggu
38 AA38 Ulsan 76 AA76 Yanggu
Open in a new tab

Figure 6.

Figure 6

Open in a new tab

(A) Sampling sites of A. annua seeds marked as black dots and their cultivation site also marked as a red dot in Korea; (B) View of cultivation fields for A. annua.

3.2. Extraction of Essential Oils

The harvested samples were stored in the cold room at 4 °C prior to the extraction of essential oils. In total, 103 AEOs were extracted from fresh aerial parts of A. annua individuals by the steam distillation extraction method. For each A. annua individual, one kilogram of the fresh sample was extracted at 100 °C for 90 min by the steam distillation apparatus (EssenLab Plus, Hanil Lab Tech Co, Ltd., Yangju, Korea). The yield of AEOs (%, v/w) was calculated as the volume (mL) of each essential oil per 1 kg plant sample. After the extraction, AEOs were purified using anhydrous sodium sulfate (Na2SO4) and were kept in the refrigerator at 4 °C.

3.3. Identification of Essential Oil Components by GC-MS Analysis

The GC-MS analysis was performed to detect the volatile components in AEOs. A GC-MS instrument (GC: Varian CP-3800 and MS: Varian 1200L, Varian, Palo Alto, CA, USA) was equipped with a fused silica VF-5MS low polarity column (30 m × 0.25 mm × 0.25 μm film thickness; Agilent, Santa Clara, CA, USA). The carrier gas used was helium at the flow rate of 1 mL/min. The GC conditions were as follows: the inlet temperature was 250 °C; the oven temperature was programmed for 50–250 °C, an increasing rate of 5 °C/min with an initial hold time of 5 min and a final hold time of one minute; the injection volume was 1 μL with split ratio 10:1. The MS conditions were as follows: the ionization mode was electron ionization; electron beam energy was set to 70 eV; the ion source temperature was 200 °C; and the mass scan range was set to 50–500 m/z. The identification of chemicals in AEOs was compared with the mass spectra data of NIST library version 3.0 and their retention indices (RI) relative to a homologous series of n-alkanes (C8–C20) with those reported in the literature data [40].

3.4. Statistical Analysis

For GC-MS analysis, the essential oil components from A. annua individuals were subjected to hierarchical cluster analysis and principal component analysis (PCA). For this purpose, the GC-MS data of 103 samples of A. annua essential oil were integrated into one data point (raw data). The chemical components in the raw data were arranged in ascending order according to their retention RI value. Only components in a concentration above 1.0% were considered for further statistical analysis. Of these, chemical components detected in over 50 individuals of A. annua were selected for PCA analysis. Multivariate and correlation analyses were undertaken based on the common chemical content of AEOs. The cluster analysis and dendrogram were constructed based on the results of PCA [15]. All statistical analyses were carried out by IBM SPSS version 26 (IBM Corp., Chicago, IL, USA).

4. Conclusions

The results demonstrate that the essential oils obtained from 103 individuals of Korean A. annua showed significant chemical diversity. Based on the chemical compositions and their relative abundances, 103 A. annua essential oils could be classified into six chemotypes such as artemisia ketone, camphor, β-cubebene, eucalyptol, α-pinene, and β-selinene. Furthermore, a multivariate analysis based on GC-MS data allowed us to identify variability among the populations of Korean A. annua. The cluster analysis and PCA revealed that A. annua individuals were divided into three large groups: artemisia ketone, eucalyptol, and β-selinene. These major components may be used as biomarkers to determine the origin of A. annua populations. These results explain that the intraspecific variations in the essential oil compositions of Korean native A. annua may be due to the influence of genetic diversity. Hence, further genetic analysis studies are warranted to confirm the observed variations within A. annua populations.

Acknowledgments

This study was carried out with the support of the “Cooperative Research Program for Agriculture Science and Technology Development (Project No. PJ014506), Rural Development Administration, Republic of Korea).

Supplementary Materials

The following supporting information can be downloaded at: https://www.mdpi.com/article/10.3390/molecules28031131/s1, Table S1. The area percent of 35 components in the essential oils of Korean Artemisia annua individuals. Table S2. Correlation coefficients between 35 components of essential oils of Korean Artemisia annua individuals.

Click here for additional data file. (699KB, zip)

Author Contributions

Conceptualization, S.K.; methodology, S.K. and M.H.; formal analysis, M.H. and M.K.; investigation, M.H., M.K., H.J. and S.B.; resources, S.K., M.H., M.K., H.J. and S.B.; data curation, M.H. and P.D.; writing—original draft preparation, M.H., P.D. and K.S.; writing—review and editing, S.K. and K.S.; supervision, S.K. All authors have read and agreed to the published version of the manuscript.

Institutional Review Board Statement

Not applicable.

Informed Consent Statement

Not applicable.

Data Availability Statement

Not applicable.

Conflicts of Interest

The authors declare that they have no conflicts of interest.

Sample Availability

Samples of essential oils of Artemisia annua are available from the authors.

Funding Statement

This research received no external funding.

Footnotes

Disclaimer/Publisher’s Note: The statements, opinions and data contained in all publications are solely those of the individual author(s) and contributor(s) and not of MDPI and/or the editor(s). MDPI and/or the editor(s) disclaim responsibility for any injury to people or property resulting from any ideas, methods, instructions or products referred to in the content.

References

  • 1.Bisht D., Kumar D., Kumar D., Dua K., Chellappan D.K. Phytochemistry and pharmacological activity of the genus Artemisia. Arch. Pharm. Res. 2021;44:439–474. doi: 10.1007/s12272-021-01328-4. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 2.Bilia A.R., Santomauro F., Sacco C., Bergonzi M.C., Donato R. Essential oil of Artemisia annua L.: An extraordinary component with numerous antimicrobial properties. Evid. Based Complement. Altern. Med. 2014;2014:159819. doi: 10.1155/2014/159819. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 3.Sharopov F.S., Salimov A., Numonov S., Safomuddin A., Bakri M., Salimov T., Setzer W.N., Habasi M. Chemical composition, antioxidant, and antimicrobial activities of the essential oils from Artemisia annua L. growing wild in Tajikistan. Nat. Prod. Commun. 2020;15:927. doi: 10.1177/1934578X20927814. [DOI] [Google Scholar]
  • 4.Feng X., Cao S., Qiu F., Zhang B. Traditional application and modern pharmacological research of Artemisia annua L. Pharmacol. Ther. 2020;216:107650. doi: 10.1016/j.pharmthera.2020.107650. [DOI] [PubMed] [Google Scholar]
  • 5.Lee Y.N. New Flora of Korea. Hyangmunsa Press; Seoul, Republic of Korea: 2006. pp. 327–334. (In Korean) [Google Scholar]
  • 6.National Insititute of Korean History (NIKH) The veritable records of the Joseon Dynasty. National Insititute of Korean History. [(accessed on 1 December 2022)];2005 Available online: http://sillok.history.go.kr/id/wda_400060. (In Korean)
  • 7.Efferth T. From ancient herb to modern drug: Artemisia annua and artemisinin for cancer therapy. Semin. Cancer Biol. 2017;46:65–83. doi: 10.1016/j.semcancer.2017.02.009. [DOI] [PubMed] [Google Scholar]
  • 8.Haq F.U., Roman M., Ahmad K., Rahman S.U., Shah S.M.A., Suleman N., Ullah S., Ahmad I., Ullah W. Artemisia annua: Trials are needed for COVID-19. Phytother. Res. 2020;34:2423–2424. doi: 10.1002/ptr.6733. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 9.Zhang X., Zhao Y., Guo L., Qiu Z., Huang L., Qu X. Differences in chemical constituents of Artemisia annua L. from different geographical regions in China. PLoS ONE. 2017;12:e0183047. doi: 10.1371/journal.pone.0183047. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 10.Abad M.J., Bedoya L.M., Apaza L., Bermejo P. The Artemisia L. Genus: A review of bioactive essential oils. Molecules. 2012;17:2542–2566. doi: 10.3390/molecules17032542. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 11.Bagchi G.D., Haider F., Dwivedi P.D., Singh A., Naqvi A.A. Essential oil constituents of Artemisia annua during different growth periods at monsoon conditions of subtropical north Indian plains. J. Essent. Oil Res. 2003;15:248–250. doi: 10.1080/10412905.2003.9712131. [DOI] [Google Scholar]
  • 12.Hong M.J., Kim M.J., Kim S. Biological activities of sweet wormwood (Artemisia annua L.) Korean J. Weed Turf. Sci. 2021;10:243–263. (In Korean) [Google Scholar]
  • 13.Ćavar S., Maksimović M., Vidic D., Parić A. Chemical composition and antioxidant and antimicrobial activity of essential oil of Artemisia annua L. from Bosnia. Ind. Crop. Prod. 2012;37:479–485. doi: 10.1016/j.indcrop.2011.07.024. [DOI] [Google Scholar]
  • 14.Hwang D.I., Won K.J., Kim D.Y., Yoon S.W., Park J.H., Kim B., Lee H.M. Anti-adipocyte differentiation activity and chemical composition of essential oil from Artemisia annua. Nat. Prod. Commun. 2016;11:539–542. [PubMed] [Google Scholar]
  • 15.Hong M.J., Deepa P., Lee K.Y., Kim K., Sowndhararajan K., Kim S. Chemical diversity of essential oils from Korean native populations of Agastache rugosa (Korean Mint) Molecules. 2022;27:6341. doi: 10.3390/molecules27196341. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 16.Kim M.J., Sowndhararajan K., Kim S. Variations in the chemical composition of essential oils in native populations of Korean thyme, Thymus quinquecostatus Celak. Molecules. 2022;27:7203. doi: 10.3390/molecules27217203. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 17.Zhigzhitzhapova S.V., Dylenova E.P., Gulyaev S.M., Randalova T.E., Taraskin V.V., Tykheev Z.A., Radnaeva L.D. Composition and antioxidant activity of the essential oil of Artemisia annua L. Nat. Prod. Res. 2019;34:2668–2671. doi: 10.1080/14786419.2018.1548461. [DOI] [PubMed] [Google Scholar]
  • 18.Radulović N.S., Randjelović P.J., Stojanović N.M., Blagojević P.D., Stojanović-Radić Z.Z., Ilić I.R., Djordjević V.B. Toxic essential oils. Part II: Chemical, toxicological, pharmacological and microbiological profiles of Artemisia annua L. volatiles. Food Chem. Toxicol. 2013;58:37–49. doi: 10.1016/j.fct.2013.04.016. [DOI] [PubMed] [Google Scholar]
  • 19.Holm Y., Laakso I., Hiltunen R., Galambosi B. Variation in the essential oil composition of Artemisia annua L. of different origin cultivated in Finland. Flavour Frag. J. 1997;12:241–246. doi: 10.1002/(SICI)1099-1026(199707)12:4&#x0003c;241::AID-FFJ641&#x0003e;3.0.CO;2-Z. [DOI] [Google Scholar]
  • 20.Zheljazkov V.D., Astatkie T., Horgan T., Schlegel V., Simonnet X. Distillation time effect on essential oil yield, composition, and antioxidant capacity of sweet sagewort (Artemisia annua L.) oil. HortScience. 2013;48:1288–1292. doi: 10.21273/HORTSCI.48.10.1288. [DOI] [Google Scholar]
  • 21.Brown G.D. The biosynthesis of artemisinin (Qinghaosu) and the phytochemistry of Artemisia annua L. (Qinghao) Molecules. 2010;15:7603–7698. doi: 10.3390/molecules15117603. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 22.Goel D., Singh V., Ali M., Mallavarupu G.R., Kumar S. Essential oils of petal, leaf and stem of the antimalarial plant Artemisia annua. J. Nat. Med. 2007;61:187–191. doi: 10.1007/s11418-006-0112-9. [DOI] [Google Scholar]
  • 23.Janaćković P., Rajčević N., Gavrilović M., Novaković J., Giweli A., Stešević D., Marin P.D. Essential oil composition of five Artemisia (Compositae) species in regards to chemophenetics. Biochem. Syst. Ecol. 2019;87:103960. doi: 10.1016/j.bse.2019.103960. [DOI] [Google Scholar]
  • 24.Shin S. In vitro effects of essential oils from the aerial parts of Artemisia annua L. against antibiotic-susceptible and -resistant strains of Salmenella typhimurium. J. Pharm. Soc. Korea. 2007;51:355–360. (In Korean) [Google Scholar]
  • 25.Bhakuni R.S., Jain D.C., Sharma R.P., Kumar S. Secondary metabolites of Artemisia annua and their biological activity. Curr. Sci. 2001;80:35–48. [Google Scholar]
  • 26.Charles D.J., Cebert E., Simon J.E. Characterization of the essential oil of Artemisia annua L. J. Essent. Oil Res. 1991;3:33–39. doi: 10.1080/10412905.1991.9697903. [DOI] [Google Scholar]
  • 27.Liu H., Guo S.-S., Lu L., Li D., Liang J., Huang Z.-H., Zhou Y.-M., Zhang W.-J., Du S. Essential oil from Artemisia annua aerial parts: Composition and repellent activity against two storage pests. Nat. Prod. Res. 2021;35:822–825. doi: 10.1080/14786419.2019.1599887. [DOI] [PubMed] [Google Scholar]
  • 28.Tzenkova R., Kamenarska Z., Draganov A., Atanassov A. Composition of Artemisia annua essential oil obtained from species growing wild in Bulgaria. Biotechnol. Biotechnol. Equip. 2010;24:1833–1835. doi: 10.2478/V10133-010-0030-6. [DOI] [Google Scholar]
  • 29.Marinas I.C., Oprea E., Chifiriuc M.C., Badea I.A., Buleandra M., Lazar V. Chemical Composition and Antipathogenic Activity of Artemisia annua Essential Oil from Romania. Chem Biodivers. 2015;12:1554–1564. doi: 10.1002/cbdv.201400340. [DOI] [PubMed] [Google Scholar]
  • 30.Santomauro F., Donato R., Pini G., Sacco C., Ascrizzi R., Bilia A.R. Liquid and Vapor-Phase Activity of Artemisia annua Essential Oil against Pathogenic Malassezia spp. Planta Med. 2018;84:160–167. doi: 10.1055/s-0043-118912. [DOI] [PubMed] [Google Scholar]
  • 31.Risaliti L., Pini G., Ascrizzi R., Donato R., Sacco C., Bergonzi M.C., Salvatici M.C., Bilia A.R. Artemisia annua essential oil extraction, characterization, and incorporation in nanoliposomes, smart drug delivery systems against Candida species. J. Drug Deliv. Sci. Technol. 2020;59:101849. doi: 10.1016/j.jddst.2020.101849. [DOI] [Google Scholar]
  • 32.Wêglarz Z., Kosakowska O., Przybył J.L., Pióro-Jabrucka E., Baczek K. The quality of Greek oregano (O. vulgare L. subsp. hirtum (Link) Ietswaart) and common oregano (O. vulgare L. subsp. vulgare) Cultivated in the temperate climate of Central Europe. Foods. 2020;9:1671. doi: 10.3390/foods9111671. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 33.Haider S.Z., Andola H.C., Mohan M. Constituents of Artemisia gmelinii Weber ex Stechm. from Uttarakhand Himalaya: A Source of Artemisia Ketone. Indian J. Pharm. Sci. 2012;74:265–267. doi: 10.4103/0250-474X.106074. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 34.Chen W., Vermaak I., Viljoen A. Camphor—A fumigant during the Black Death and a coveted fragrant wood in ancient Egypt and Babylon—A review. Molecules. 2013;18:5434–5454. doi: 10.3390/molecules18055434. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 35.Ivanov M., Kannan A., Stojković D.S., Glamočlija J., Calhelha R.C., Ferreira I.C.F.R., Sanglard D., Soković M. Camphor and Eucalyptol-Anticandidal Spectrum, Antivirulence Effect, Efflux Pumps Interference and Cytotoxicity. Int. J. Mol. Sci. 2021;22:483. doi: 10.3390/ijms22020483. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 36.Cai Z.M., Peng J.Q., Chen Y., Tao L., Zhang Y.Y., Fu L.Y., Long Q.D., Shen X.C. 1,8-Cineole: A review of source, biological activities, and application. J. Asian Nat. Prod. Res. 2021;23:938–954. doi: 10.1080/10286020.2020.1839432. [DOI] [PubMed] [Google Scholar]
  • 37.Allenspach M., Steuer C. α-Pinene: A never-ending story. Phytochemistry. 2021;190:112857. doi: 10.1016/j.phytochem.2021.112857. [DOI] [PubMed] [Google Scholar]
  • 38.Yu Y., Bai J., Chen C., Plotto A., Baldwin E.A., Gmitter F.G. Comparative analysis of juice volatiles in selected mandarins, mandarin relatives and other citrus genotypes. J. Sci. Food Agric. 2018;98:1124–1131. doi: 10.1002/jsfa.8563. [DOI] [PubMed] [Google Scholar]
  • 39.Vella F.M., Calandrelli R., Cautela D., Fiume I., Pocsfalvi G., Laratta B. Chemometric Screening of Fourteen Essential Oils for Their Composition and Biological Properties. Molecules. 2020;25:5126. doi: 10.3390/molecules25215126. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 40.Adams R.P. Identification of Essential Oil Components by Gas Chromatography/Mass Spectrometry. Allured Publishing Co., Ltd.; Carol Stream, IL, USA: 2007. [Google Scholar]

Associated Data

This section collects any data citations, data availability statements, or supplementary materials included in this article.

Supplementary Materials

Click here for additional data file. (699KB, zip)

Data Availability Statement

Not applicable.

Articles from Molecules are provided here courtesy of Multidisciplinary Digital Publishing Institute (MDPI)

RESOURCES