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Chemical constituents and biological activities of essential oil from
Mentha longifolia: eects of dierent extraction methods
Xiaohui Bai
a,b
, Aoken Aimila
a,b
, Nurbolat Aidarhan
a
, Xiaomei Duan
a,b
,
and Maitinuer Maiwulanjiang
a
a
State Key Laboratory Basis of Xinjiang Indigenous Medicinal Plants Resource Utilization, Xinjiang Technical Institute of
Physics and Chemistry, and the Key Laboratory of Plant Resources and Chemistry of Arid Zone, Xinjiang Technical
Institute of Physics and Chemistry, Chinese Academy of Sciences, Urumqi, China;
b
School of Chemical Science,
University of the Chinese Academy of Sciences, Beijing, China
ABSTRACT
Mentha longifolia: . is a perennial herb of Mentha in Labiatae. Considering
the biological activities of Mentha longifolia essential oils, this work was
planned to study the yields, relative percentage content and semi-
quantitative change of chemical constituents as well as the biological activ-
ities of essential oils extracted by dierent extraction methods. Steam-
distillation (SD), lipophilic solvents (n-hexane) extraction (LSE) and super-
critical CO
2
uid extraction (SC-CO
2
) were employed to produce essential oils
from Mentha longifolia. The essential oil obtained from LSE (1.21 ± 0.06%, w/
w) showed the highest yield. A total of 39 compounds were identied by gas
chromatography/ame ionization detector (GC-FID) and gas chromatogra-
phy/mass spectrometry (GC-MS). The major compounds in SD and LSE were
carvone, limonene, trans-caryophyllene and α-Terpineol, the major com-
pounds in SC-CO
2
were carvone, trans-caryophyllene, trans-β-Farnesene
and Germacrene D. All essential oils showed varying degrees of antioxidant
and anti-COX-2 activity. The IC
50
ranging from (0.69 ± 0.01 ~ 15.61 ± 0.16 mg/
mL) for DPPH and (0.16 ± 0.001 ~ 2.19 ± 0.11 mg/mL) for ABTS, SC-CO
2
produced essential oil showed the highest scavenging activity both on DPPH
and ABTS. Meanwhile, all the EOs showed the strong inhibition activity on
COX-2, the EO obtained by SC-CO
2
also showed the highest capacity to
inhibit COX-2.
ARTICLE HISTORY
Received 6 August 2020
Revised 27 September 2020
Accepted 1 October 2020
KEYWORDS
Mentha longifolia; essential
oil; extraction method;
chemical constituents;
antioxidant; COX-2
Introduction
Mentha longifolia is a perennial herb of Mentha in Labiatae. The tender leaves are not only common
dishes, but also are an important flavoring. Mentha longifolia also is a commonly medicinal plant
source. Mentha longifolia has been used in traditional medicine practices for the treatment of
bronchitis, headache, cough, nausea, asthma, liver diseases, digestive disorders, stomach, abdominal
disorders, etc.
[1,1, 2]
Essential oil (EO) of Longifolia possesses a plethora of biological activities such as
antispasmodic, anticancerous, antimicrobial, antioxidative, insect repellent, and neuroprotective
effects.
[3,4]
EO can be obtained from plants by many methods, including steam-distillation (SD), lipophilic
solvents extraction (LSE) and supercritical CO
2
fluid extraction (SC-CO
2
).
[5]
Extraction methods have
obvious influence on quality and exact chemical compositions of EO. Inflammation is one of the most
common autoimmune diseases in our life. It is a complex natural defense mechanism of organism to
CONTACT Maitinuer Maiwulanjiang mavlanjan@ms.xjb.ac.cn Xinjiang Key Laboratory of Plant Resources and Natural
Products Chemistry, Xinjiang Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Urumqi, Xinjiang 830011,
China
INTERNATIONAL JOURNAL OF FOOD PROPERTIES
2020, VOL. 23, NO. 1, 1951–1960
https://doi.org/10.1080/10942912.2020.1833035
Published with license by Taylor & Francis Group, LLC.
This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0/),
which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
infection or tissue damage.
[6]
Free radicals and COX-2 are two important factors in the process of
inflammation. Free radicals are the most common inflammatory mediators.
[7]
When inflammation
occurs, COX-2 is highly expressed in the body, which plays a key role in the induction and
maintenance of inflammatory pain.
[8]
It is well known that nonsteroidal anti-inflammatory drugs
(NSAIDs) have good effects on treating inflammatory, but it also induces serious gastrointestinal
reactions. Therefore, natural anti-inflammatory products are attracting more attention. EO is naturally
synthesized in aromatic plants as secondary metabolites, having a wide array of bioactivities with
minimal or zero toxicity to the mammals.
[5,9]
To the best of our knowledge, application of SC-CO
2
to
obtain essential oil from M. longifolia has not been previously reported. There is also negligible report
available to compare the chemical constituents by semi-quantitative and biological activities, including
the anti-COX-2 and antioxidant properties of essential oils which are obtained from different extrac-
tion methods. In this work, we investigated the yields, chemical constituents, and biological activities
of EO extracted from M. longifolia by different methods, including, SD, LSE and SC-CO
2
. The EOs
were analyzed by gas chromatography/flame ionization detector (GC-FID, equipped with polar and
apolar capillary column) and gas chromatography/mass spectrometry (GC-MS). In order to identify
the most effective extraction method, we investigated 2,2-diphenyl-1-picryl-hydrazyl-hydrate
(DPPH), 2,2ʹ-Azinobis-(3-ethylbenzthiazoline-6-sulfonate) (ABTS) assays for antioxidant activities
and inhibition effect of EO on COX-2. Moreover, the results of the present study might be of help to
finding high-quality essential oil with anti-inflammatory activity.
Materials and methods
Plant material and reagents
The aerial part of fresh plant materials were collected at the countryside of Kuche, in the province of
Xinjiang, China in June 2019. The voucher of the species used in this study was deposited in the
Xinjiang Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, with specimen
number No. WY02663. The picked fresh M. longifolia was spread in the room without direct sunlight
(25 ± 6°C) and natural ventilation. Drying process was continued for 14 days until constant weight and
mechanically ground to a homogenous powder on a laboratory grinder.
2,2-diphenyl-1-picryl-hydrazyl-hydrate (DPPH, purity≥98%), 2,2ʹ-Azinobis-(3-ethylbenzthiazo-
line-6-sulfonate) (ABTS, purity≥98%), tocopherol (purity≥98%), methyl octanoate (purity≥98%)
and PGE2 (Prostaglandin E2) ELISA Kit (48 T). All other chemicals and solvents (n-hexane, anhy-
drous alcohol) used in the present study were analytical grade.
Extraction of essential oil
Steam-distillation
The 100 g of plant samples were extracted in a Clevenger apparatus. Fresh distilled water was used as
extraction solvent and the ratio of material to liquid was 1:10. After four hours, the EOs were collected
and dried by sodium sulfate anhydrous and then stored at 4°C until analysis.
[10]
The extraction was
performed three times.
Supercritical fluid extraction
SC-CO
2
extraction was performed on a 1 L-SFE221-50-06 Supercritical CO
2
Extraction System. The
50 g of plant materials were added to high present extraction kettle. The liquefied CO
2
was introduced
into the sample cartridge through a pump with a cooling jacket. The flow rate of CO
2
was 5 L/min; the
extraction pressure was 20 MPa, the static extraction time were 30 minutes and the dynamic extraction
time were 120 minutes, respectively.
[11]
Extracts were finally separated from the CO
2
phase and
1952 X. BAI ET AL.
collected in collection bottle at ambient temperature and atmospheric pressure. The extraction was
performed three times.
Lipophilic solvent extract
The 50 g of plant materials were soaked in 250 mL of n-hexane for 24 hours at room temperature (RT,
25 ± 6°C), the operation repeated for 5 times. Then, the supernatants were mixed, filtered, and
evaporated n-hexane under reduced pressure.
[12]
The extraction was performed three times and the
yield of EO was calculated according to formula 1
[13]
as follows:
The yield of essential oil (%)
¼M1
M2 x100 (1)
where M1 is the weight of collected essential oil (g) and M2 is the total weight of the plant material (g).
Chemical compositions analysis of EO by GC-FID
Analysis was carried out with an Agilent Technologies 7890B GC system equipped with flame
ionization detectors. EO was analyzed by HP-5 (5%-phenyl)-methylpolysiloxane) apolar capillary
column and HP-INNOWax (polyethylene glycol) polar capillary column. The oven temperature was
started at 60°C for 5 min and raised to 240°C at rate of 4°C/min. The temperature of the injector and
detector was set at 250°C. The carrier gas was nitrogen with a flow of 1.5 mL min
−1
. A sample of 0.3 μL
was injected (split ratio 30:1). The polarity retention index (RI
p
) and apolar retention index (RI
a
) of
each compound were calculated by using a series of n-alkanes (C
7
–C
40
). Methyl octanoate was used as
an internal reference; the correction factor (CF) of each compound was calculated according to the
calculation method described in literature.
[13]
The result is shown in Table 1.
Chemical compositions analysis of EO by GC-Q-TOF-MS
The essential oil was analyzed with an Agilent Technologies 7890B GC system equipped with
Quadrupole-Time of Flight Mass Spectrometer (Q-TOF-MS) and equipped with fused-silica capillary
column (30 m × 0.25 mm i.d., film thickness 0.25 μm), HP-5 MS (5%-phenyl)-methylpolysiloxane).
Injector temperature was set at 250°C. The carrier gas was nitrogen with a flow of 1 mL min
−1
. A sample
of 0.3 μL was injected (split ratio 30:1). The oven temperature was started at 60°C for 5 min and then
increased to 240°C at rate of 4°C/min. For GC-Q-TOF-MS detection, an electron impact ionization
mode, with ionization energy of 70 eV was used. Mass range was 50 ~ 500 m/z while the injector and
MS transfer line temperatures were set at 250 and 150°C, respectively.
[14]
The components in essential
oil were identified by comparing their retention index (RI) and mass spectra with NIST 14 libraries.
Antioxidant activity
DPPH radical-scavenging assay
The antioxidant ability of EO against DPPH radical scavenging was based on Reis et al.
[15]
with slightly
modified. Briefly, the EO sample (100 μL) at different concentrations was mixed with 100 μL of
0.2 mmol/L DPPH solution. The absorbance was measured at 517 nm by microplate reader (bio-red
550) after the reaction was incubated in the dark at room temperature for 30 minutes. The blank
control was the EO solution of corresponding concentration.
ABTS radical-scavenging assay
The ABTS radical scavenging assay was measured based on R. Re et al.
[16]
The ABTS stock solution
was produced by mixed 7 mM ABTS solution with 2.45 mM potassium persulfate solution, and kept in
INTERNATIONAL JOURNAL OF FOOD PROPERTIES 1953
the dark at room temperature for 16 h before used. Then, the ABTS stock solution was diluted with
absolute alcohol to an absorbance of approximately 0.70 at 734 nm. The EOs (100 μL) at different
concentrations was mixed with ABTS (100 µL) solution. The absorbance was measured at 734 nm by
microplate reader after the reaction was incubated in the dark at room temperature for 5 minutes. The
blank control was the EO solution of corresponding concentration. The scavenging ability of EO to
radical was calculated according to formula 2
[17]
:
Scavenging rate (%)
¼Ad Ae Abg
Ad x100 (2)
Ad is the absorbance of free radical solution does not contain sample, Ae is the absorbance of reaction
solution and Abg is the background color of EO.
Table 1. Volatile compounds identified in extracts of Mentha longifolia prepared by different extraction methods.
NO RT Components RI RI
a
Extraction Methods
SD LSE SC-CO
2
A% g/100 g A% g/100 g A% g/100 g
1 6.51 α-Pinene 929 932 0.54 0.43 0.28 0.08 - -
2 7.93 β-Thujene 966 972 0.37 0.28 0.21 0.06 - -
3 8.03 Sabinene 974 974 0.71 0.53 0.43 0.12 - -
4 8.60 β-Myrcene 991 990 0.30 0.23 0.14 0.04 - -
5 10.06 Limonene 1023 1029 30.10 23.14 14.66 4.23 0.23 0.03
6 10.11 Eucalyptol 1032 1030 0.31 0.31 0.65 0.19 - -
7 10.41 (Z)-Ocimene 1038 1038 0.39 0.30 0.09 0.02 - -
8 10.81 (E)-Ocimene 1049 1048 0.20 0.15 - - - -
9 12.78 Linalool 1099 1099 - - - - 0.30 0.01
10 14.80 trans-Menthone 1154 1153 0.56 0.54 - - - -
11 15.20 cis-Menthone 1164 1164 - - 0.12 0.02 - -
12 15.34 Lavandulol 1170 1167 - - 0.29 0.05 0.17 0.02
13 16.18 α-Terpineol 1189 1190 1.47 1.43 1.34 0.42 0.79 0.10
14 16.41 1,6-Dihydrocarveol 1195 1196 0.92 0.93 0.20 0.05 0.26 0.03
15 16.57 Dodecane 1200 1200 - - 0.12 0.03 0.15 0.02
16 17.24 trans-Carveol 1217 1219 0.32 0.31 0.32 0.08 0.43 0.06
17 17.71 cis-Carveol 1229 1232 0.38 0.39 0.39 0.11 0.14 0.02
18 17.97 cis-3-Hexenyl isovalerate 1238 1239 1.01 1.23 - - - -
19 18.25 Carvone 1248 1247 52.81 55.82 47.52 13.18 33.07 4.50
20 18.49 Piperitone 1253 1254 0.27 0.28 1.03 0.27 1.50 0.20
21 19.51 α-Terpinen-7-al 1283 1283 0.23 0.24 - - - -
22 19.75 2-Caren-10-al - 1290 0.33 0.35 0.05 0.09 0.24 0.03
23 20.14 Carvacrol 1299 1301 - - 0.13 0.03 0.34 0.05
24 22.22 cis-Carvyl acetate 1362 1364 0.15 0.18 0.10 0.03 0.22 0.03
25 22.64 Copaene 1376 1376 0.19 0.13 0.25 0.06 0.19 0.02
26 22.94 β-Bourbonene 1384 1385 1.12 0.08 0.91 0.21 1.05 0.12
27 23.37 Jasmone 1394 1398 0.24 0.26 0.72 0.19 1.36 0.18
28 23.65 cis-caryophyllene 1406 1407 0.08 0.05 0.10 0.02 0.16 0.02
29 24.05 trans-caryophyllene 1419 1420 2.59 1.88 2.70 0.62 4.87 0.55
30 24.36 β-Copaene 1432 1430 0.12 0.09 0.15 0.03 0.24 0.03
31 24.83 Isogermacrene D 1448 1445 0.10 0.07 0.11 0.03 0.19 0.02
32 25.11 Humulene 1454 1454 0.27 0.19 0.04 0.03 - -
33 25.23 trans-β-Farnesene 1457 1458 0.07 0.05 1.05 0.24 2.26 0.25
34 25.98 Germacrene D 1481 1482 0.70 0.51 0.99 0.23 2.09 0.24
35 26.46 Bicyclogermacrene 1495 1497 0.26 0.19 0.47 0.11 1.23 0.14
36 27.27 δ-Cadinene 1524 1525 0.11 0.08 0.19 0.04 0.74 0.08
37 28.86 Spathulenol 1577 1579 - - 0.35 0.08 0.89 0.11
38 29.03 Caryophyllene oxide 1581 1584 0.15 0.13 0.26 0.08 0.77 0.10
39 35.94 Perhydrofarnesyl acetone - 1840 - - 4.17 0.11 0.56 0.07
RT: Retention times, RI: Theoretical retention index of compounds on HP-5 apolar capillary column, RI
a
: Experimental retention index
of compounds on HP-5 apolar capillary column, A%: Relative content of individual compounds calculated by area normalization
method, g/100 g: semi-quantitative analysis results of component, each value is represented in terms of average mean (n = 3).
1954 X. BAI ET AL.
COX-2 inhibition assay
Enzyme immunoassay (EIA) was used to determine the inhibitory activity of sample to COX-2.
[18]
The
determination process can be divided into the following steps: First, prepare reaction solutions with
various concentrations according to the instructions of the kit (Multi Sciences (Lianke) Biotechnology
Corporate Limited), prepare positive control solutions (celecoxib:1 μmoL/mL) and EO sample solu-
tions (100 μg/mL). Secondly, sample solutions (EO and celecoxib) react with COX-2. Then, the
substrate arachidonic acid (AA) was added, and AA was catalyzed to prostaglandin (PG) by COX-2.
Then, the enzyme-labeled pore was stained with3,3ʹ,5,5ʹ-tetramethylbenzidine (TMB). The optical
density (OD) was measured at 450 nm (absorption wavelength) and 570 nm (reference wavelength) by
microplate reader. The inhibition ability of EO to COX-2 was calculated according to formula 3.
[19]
Inhibition rate (%)
¼1Ae Aec
Ac Acc
x100 (3)
Ae is the absorbance of the EOs, Aec is the absorbance of the EOs control group, Ac is the absorbance
of the enzyme activity group, Acc is the absorbance of the enzyme activity control group.
Statistical analysis
All assay was performed with three repetitions in independent experiments. The statistical analysis was
performed by the one-way analysis of variance (ANOVA), and p < .05 or p < .01 of the difference
means was considered to be significant.
Results and discussion
Yield of essential oil extracted by dierent methods
An ANOVA statistical analysis was used to analyze the significant difference among the yield of EO
extracted by different methods (p < .05). The highest yield of EO was obtained by LSE (1.21 ± 0.06%,
w/w) method, followed by SC-CO
2
(1.09 ± 0.08%, w/w) method and the lowest yield was SD
(0.82 ± 0.16%, w/w). The result was shown in Figure 1. This is consistent with a previous report
that LSE was the optimal process for obtaining a high yield of EOs from lavender.
[20]
Supercritical fluids generally display physicochemical properties between of a liquid and gas,
typically characterized by low viscosity, high density, and diffusivity, its viscosity is smaller than the
liquid and diffusion speed faster than the liquid, therefore, supercritical fluids have better fluidity and
transmission performance,
[21]
Theoretically, based on the characteristics of supercritical fluid, the
yield of EO produced by SC-CO
2
might was higher than LSE, but the result showed that the yield of
LSE was slightly higher than SC-CO
2
, it may due to LSE extract contain more plant pigments.
Identication of the chemical compounds from M. longifolia essential oil
Peak area normalizing method and internal standard method were used to determine the relative
contents and semi-qualification of the compounds in the EO (Tables 1 and 2). A total of 39
compounds were identified by GC/MS and GC/FID, including eight aldehydes and ketones, 18
monoterpenes and sesquiterpenes, nine alcohols, two esters and two others compounds. Peak area
normalizing method showed that terpenes (38.22 ± 1.53%-13.25 ± 0.87%) compounds and aldehydes
and ketones (54.44 ± 1.62%-36.73 ± 1.44%) compounds made the most important contribution for
essential oil of M. longifolia. An ANOVA statistical analysis showed that the contents of major
compounds in three EO had significant difference (p < .01). The main components in SD and LSE
were carvone (52.81 ± 0.46% and 47.52 ± 1.37%), limonene (30.10 ± 0.37% and 14.66 ± 0.81%),
INTERNATIONAL JOURNAL OF FOOD PROPERTIES 1955
respectively, trans-caryophyllene (2.59 ± 0.11% and 2.70 ± 0.69%) and α-terpineol (1.34 ± 0.09%-
1.47 ± 0.13%), the major compounds in the EO produced by SC-CO
2
were carvone (33.07 ± 1.54%),
trans-caryophyllene (4.87 ± 0.29%), trans-β-farnesene (2.26 ± 0.15%) and germacrene
D (2.09 ± 0.16%) respectively.
The identified 39 compounds in the EO accounted for 91.54 ± 0.72 g/100 g by SD, 21.41 ± 1.35 g/
100 g by LSE and only 7.15 ± 0.61 g/100 g by SC-CO
2
. The compositions of EO extracted by SD were
mainly made up of volatile components, and the compositions of EO extracted by LSE and SC-CO
2
were mainly formed by high boiling point and nonvolatile components. The content of limonene in
the EO was 23.14 ± 0.19 (g/100 g) extracted by SD, 4.23 ± 0.34 (g/100 g) in LSE and only 0.03 ± 0.004
(g/100 g) in SC-CO
2
. In addition, α-pinene, β-thujene, sabinene, β-myrcene, eucalyptol, and (Z)-
ocimene were not be detected in the essential oil by SC-CO
2.
It might be due to the lower boiling point
of those compounds, and those compounds volatilized during the continuous purging of the collection
bottle by carbon dioxide fluid.
SD SC-CO2 LSE
0.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
a
a
Yield(%)
Extraction methods
b
Figure 1. Yield of essential oil extract by different methods, SD was the essential oil obtained by steam-distillation, SC-CO
2
was
supercritical CO
2
fluid extraction and LSE was organic solvent extract. Means in the same row followed by different letters are
significantly different (p < .05). Each value is represented in terms of mean (n = 3) ± SD (Standard deviation).
Table 2. Numbers of the classes of compounds in extracts obtained by different extraction methods.
Classification of compounds
SD LSE SC-CO
2
A% g/100 g A% g/100 g A% g/100 g
Aldehydes and ketones 54.44 57.49 53.61 13.86 36.73 4.98
Terpenes 38.22 28.38 22.77 6.17 13.25 1.50
Alcohols 3.40 3.37 3.67 1.01 3.32 0.40
Esters 1.16 1.41 0.10 0.03 0.22 0.03
Others 0.15 0.13 0.38 0.11 0.92 0.12
Total 97.37 90.78 80.53 21.18 54.44 7.03
A%: Relative content of individual compounds calculated by area normalization method, g/100 g: semi-quantitative analysis results of
component, each value is represented in terms of average mean (n = 3).
1956 X. BAI ET AL.
Antioxidant activity
A large number of free radicals lead to disease deterioration, inflammation, radiation damage and
ischemia in the body.
[22]
Other studies had confirmed that free radicals can promote the progression and
persistence of inflammatory reaction, which may be related to the lipid peroxidation induced by free
radicals in vivo.
[23]
Therefore, it is necessary to evaluate the ability of EO to scavenge the free radicals.
Two groups of experiments (DPPH and ABTS) were conducted to evaluate the antioxidant activity
of EO (Figure 2 and Table 3), with tocopherol as a positive control. IC
50
values (mg/mL) calculated
from log dose inhibition curves were expressed as means ± standard deviation (SD) of triplicate
0 1 2 3 4 5
0
20
40
60
80
100
Scavenging rate (%)
DPPH
LSE
SC-CO2
0 10 20 30 40 50
0
20
40
60
80
100
S D
0.0 0.5 1.0 1.5 2.0 2.5
0
20
40
60
80
100
Scavenging rate (%)
ABTS
LSE
SC-CO
2
0 5 10 15 20 25 30
0
20
40
60
80
100
S D
Figure 2. Scavenging ability of EOs against DPPH (upper panel) and ABTS (lower panel) free radicals, SD corresponds to the upper X-
axis, LSE and SC-CO
2
corresponds to the lower X-axis, the value of each point is represented in terms of mean (n = 3) ± SD (Standard
deviation).
INTERNATIONAL JOURNAL OF FOOD PROPERTIES 1957
experiments. Higher DPPH radical scavenging activities were associated with lower IC
50
values. An
ANOVA was used to analyze the significant (p < .01) variation in the radical scavenging activity of
essential oil and different extracts. Extracting methods had an obvious effect on the antioxidant
activity of essential oil. The essential oil extracted by SC-CO
2
presented the highest radical scavenging
activity both on DPPH (0.69 ± 0.014 mg/mL) and ABTS (0.156 ± 0.001 mg/mL), and the IC
50
value of
SC-CO
2
on DPPH was better than positive control, but the IC
50
value on ABTS was weaker than
positive control. Followed by the EO extracted by n-hexane (DPPH: 1.58 ± 0.03 mg/mL, ABTS:
0.42 ± 0.006 mg/mL), and the lowest was SD (DPPH: 15.61 mg/mL, ABTS: 2.19 ± 0.11).
More variety of compounds were contained in the EO extracted by SC-CO
2
method, because of the
enhanced transport properties, low viscosity and moderately high diffusivity
[21]
the supercritical CO
2
fluids possessed. According to reports, the antioxidant activities of essential oils may act synergistically
and the activity may be higher than a single compound.
[24]
COX-2 inhibitory activity
The essential oil extracted by different methods were also evaluated for inhibitory effect against COX-2
activity with celecoxib (1 μM/mL) was used as positive control. An ANOVA was used to analyze the
significant (p < .05) variation in the COX-2 inhibitory activity of essential oil (Figure 3). SC-CO
2
(100%) showed the highest inhibition rate on COX-2, followed by LSE (96.85 ± 2.68%) and the lowest
Table 3. Antioxidant activities of essential oils extracted by different methods.
Sample
IC
50
(mg/mL)
DPPH ABTS
SD 15.61 ± 0.16a 2.19 ± 0.11a
LSE 1.58 ± 0.03b 0.42 ± 0.006 b
SC-CO
2
0.69 ± 0.014d 0.156 ± 0.001 c
Tocopherol 1.30 ± 0.02 c 0.023 ± 0.0005d
Means in the same row followed by different letters are significantly different (p < 0.01). Each
value is represented in terms of mean (n = 3) ± SD (Standard deviation).
Celecoxib SC-CO2 LSE S D
0
20
40
60
80
100
b
b
a
Inhibition(%)
Extraction methods
a
Figure 3. The inhibit rate of EOs extracted by different methods on COX-2, means in the same row followed by different letters are
significantly different (p < .05), each value is represented in terms of mean (n = 3) ± SD (Standard deviation).
1958 X. BAI ET AL.
was SD (65.55 ± 8.87%). The inhibitory effects of EO obtained by SC-CO
2
and LSE on COX-2 had
a significant difference from positive control and EO obtained by SD (p < .05), the result showed that
extraction methods has a great effect on the properties of essential oil.
Conclusion
In this study, various extraction methods were used to analyze the essential oil obtained from
M. longifolia. The highest yield of the EO was obtained by LSE method. The SD produced EO
possessed the most principal component (carvone and limonene). The most bioactive essential oil
was extracted by SC-CO
2
method. These results indicated that the extraction methods had significant
impact on the yield, chemical composition and bioactivities of EOs. Therefore, the type of extraction
method could be chosen according to the purpose of the use of essential oil.
Compliance with ethical standards
The authors declare that there is no conflict of interest in this study.
Funding
This work was supported by the Recruitment Program of Global Expert awarded to Maiwulanjiang, and the Director
Foundation of XTIPC, CAS (2016RC002).
ORCID
Xiaohui Bai http://orcid.org/0000-0001-6988-1561
Maitinuer Maiwulanjiang http://orcid.org/0000-0003-2328-3974
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