Mineral contents and essential oil composition of lemon thyme (Thymus citriodorus l.) and lemon verbena (Lippia citriodora L.)

Abstract

Lavender (Lavandula angustifolia MILLER) is an important medicinal plant that is known for its excellent aroma and is extensively used in the perfumery, flavour and cosmetic industries. It contains important chemical compounds like linalool and linalyl acetate as the major components in its essential oils1. These components show variations due to many factors mainly differences among plant genotypes or to the altitude and microclimate of the cultivation area.
The present study aimed to determine mineral content, chemical compositions of hydro-distilled essential oil, antimicrobial and antioxidant activities of essential oil of lavender.
The dried flowers of lavender were extracted by hydro-distillation. The essential oil composition was analyzed by gas chromatography-mass spectrometry (GC/MS) and microelement contents of herbs were examined by Perkin Elmer Optima 2100 DV ICP OMS. For antimicrobial activity, the disc diffusion tests were carried out on E. coli line ATCC25922, P. aeroginosa line ATCC27853, S. aureus line 25923, S. pyogenes line ATCC19615 and C. albicans line ATCC10231, and the antioxidant activity was performed by using DPPH radical-scavenging method.
It was determined that essential oil of L. angustifolia contains linalool, lavandulyl acetate and linalyl acetate as major components. Treatment of 10µL of the oil exhibited strong antimicrobial activity against C. albicans and moderate activity against S. pyogenes, S. aureus and E. coli. The essential oil of L. angustifolia exhibited 48% inhibition that is higher compared to the activity exhibited by butylated hydroxytoluene (BHT); which was used as positive control.

Full text

ESSENTIAL OIL AND MICROELEMENT COMPOSITION OF LEMON VERBENA AND LEMON THYME
97
DOI: 10.1515/cerce-2016-0018
Available online: www.uaiasi.ro/CERCET_AGROMOLD/
Print ISSN 0379-5837; Electronic ISSN 2067-1865
Cercetări Agronomice în Moldova
Vol. XLIX , No. 2 (166) / 2016: 97-105
ESSENTIAL OIL AND MICROELEMENT
COMPOSITION OF THYMUS CITRIODORUS L. AND
LIPPIA CITRIODORA H.B.K.
S. KIZIL 1*, Ö. TONÇER1
* E-mail: suleymankizil@gtmail.com
Received October 05, 2015. Accepted: April 06, 2016. Published online: June 30, 2016
1 Department of Field Crops, Agriculture Faculty, Dicle University, Diyarbakır, Turkey
Abstract. Lemon verbena (Lippia
citriodora H.B.K., Verbenaceae family) is
indigenous to South America and cultivated
as an aromatic plant in various parts of
world. Lemon thyme (Thymus citriodorus
L.), Lamiaceae family, is a perennial
medicinal plant native to southern Europe
and is cultivated in the Mediterranean
region. These species are cultivated mainly
for the lemon-like aroma emitted from their
leaves due to the presence of dimethyl-2,6-
octadienal, also known as lemonal or citral,
which is used in food and perfumery for its
citrus effect. The aim of this study was to
determine the mineral content and essential
oil components of L. citriodora and
T. citriodorus plants grown under semi-arid
climatic conditions in Turkey. The aerial
parts of lemon thyme and lemon verbena
plants were extracted using hydro-
distillation. The essential oil composition
was analyzed by gas chromatography-mass
spectrometry (GC-MS) and the
microelement contents of the herbs were
examined via inductively coupled plasma-
optical emission spectrometry (ICP-OES).
The microelement contents were 0.249,
1.630, 16.41, 0.106, and 13.1-36.2 mg kg-1
for cadmium (Cd), copper (Cu), iron (Fe),
and manganese (Mn), respectively, in lemon
thyme, and 0.275, 4.584, 248.1, 15.71, and
1.803 mg kg-1 for Cd, Cu, Fe, Mn, and zinc
(Zn), respectively, in lemon verbena. Fifty
compounds were identified in lemon
verbena essential oil, including limonene
(30.33%), trans-citral (17%), cis-citral
(12.77%), caryophyllene oxide (5.71%), and
geraniol acetate (4.02%) that together
constituted 99.86% of the oil composition.
We also identified 22 compounds
constituting approximately 85.11% of
lemon thyme essential oil, including trans-
geraniol (30.07%), trans-citral (15.06%),
cis-citral (11.71%), cis-geraniol (7.65%),
and 3-octanol (6.18%).
Keywords: lemon tyme; lemon verbena;
lemonal; citral; oil composition.
INTRODUCTION
Lemon verbena (Lippia
citriodora H.B.K.) is native to South
America and grows wild in Chile,
Peru, and Argentina. The Lippia

S. KIZIL, Ö. TONÇER
98
genus (Verbenaceae family) contains
more than 200 species and Lippia spp.
exhibit a wide range of genetic
diversity for essential oil composition
in various locations throughout the
world (Argyropoulou et al., 2007).
Most Lippia species have been used
mainly for gastrointestinal and
respiratory diseases in traditional
medicine. Some species of the herb
are used for their antimalarial,
antiviral, and cytostatic properties.
The therapeutic effects of these herbs
are conferred by their essential oils
and phenolic compounds (flavonoids)
(Catalan and Lampasona, 2002;
Argyropoulou et al., 2007; Malekirad
et al., 2011). The major constituents
of Lippia essential oil were previously
reported to be 1,8-cineole (12.4%),
geranial (9.9%), 6-methyl-5-hepten-2-
one (7.4%), and neral (6.9%)
(Bellakhdar et al., 1994), while
1,8-cineole was also reported to be a
major component of the oil in another
study (Malekirad et al., 2011).
Lemon thyme (Thymus
citriodorus L.) is a perennial and
medicinal plant indigenous to
southern Europe and is a member of
the Lamiaceae family. Lemon thyme
plants are cultivated in Mediterranean
countries and grows to a height of
approximately 20-40 cm and has hairy
leaves and stems, opposite leaves, and
half-grained white flowers that are
small and pink in colour. Lemon
thyme is a lemon-scented herb used in
herbal teas. The essential oil is rich in
geraniol (60%); other constituents
include geranyl acetate (1.0%),
geranyl butyrate (0.8%), nerol (2.8%),
and citronellol (0.3%). The lemon
fragrance is conferred by geranial and
neral, which contribute 8.2 and 5.5%,
respectively, to the total oil
composition. Thymol is found in
small (0.5%) quantities in the oil
(Stahl-Biskup and Holthuijzen, 1995).
The essential oils of medicinal
and spice plants are used in industry
for their flavour and fragrance
chemistry and for flavouring foods,
drinks, and many other products.
Essential oils can be used as
alternative treatments for various
diseases. Lemon verbena and lemon
thyme essential oils contain citral and
its isomers, geranial and neral, and are
cultivated mainly because of the
lemon-like aroma of their leaves. This
lemon-like scent is caused by the
presence of dimethyl-2,6-octadienal,
also known as lemonal or citral,
which is used in several chemical
industries. It also has strong
antimicrobial activity and pheromonal
effects on insects (Hapke et al., 2001).
In addition, medicinal and spice plants
contain essential trace elements,
which may be beneficial to human
health through consumption of the
herbs. Recent scientific studies have
demonstrated the importance of trace
elements to human health and related
studies on the mineral compositions
of herbs, spices, and other crops are
increasing worldwide.
The aim of this study was to
determine the essential oil and
microelement composition of Thymus
citriodorus and Lippia citriodora
plants, cultivated in the Southeast
Anatolia, region of Turkey, and to

ESSENTIAL OIL AND MICROELEMENT COMPOSITION OF LEMON VERBENA AND LEMON THYME
99
compare the results with those of
studies conducted under different
ecological conditions.
MATERIALS AND METHODS
Plant materials
Lemon verbena and lemon thyme
seedlings were obtained from the Ataturk
Central Horticultural Research Institute,
Yalova, Turkey. Cuttings of L. citriodora
were rooted in a sandbox and then
transferred to the collection garden
(Department of Field Crops, Agriculture
Faculty, Dicle University, Diyarbakir,
Turkey) in April 2009. Lemon verbena
and lemon thyme were harvested at
flowering in July and September,
respectively, of 2010.
Essential oil extraction
Essential oil was extracted from
20 g dry herbage samples by
hydrodistillation for 3 h, under continuous
steam using a Clevenger-type apparatus
(v/w). The isolated oils were stored in
tightly closed vials at 4°C until analysis.
Mineral content
The mineral contents of the samples
were determined via inductively coupled
plasma-optical emission spectrometry
(ICP-OES), using an Optima 2100 DV
system (PerkinElmer, Inc. Shelton, CT,
USA)
Identification of essential oils
Lemon verbena and lemon thyme
essential oils were analysed via gas
chromatography-mass spectroscopy
(GC-MS) using a Clarus 600 C gas
chromatograph in tandem with a Clarus
600 mass spectrometer (PerkinElmer),
equipped with an auto sampler. Sample
volumes of 1 μL were injected using the
split method. Chromatographic
separations were accomplished using an
Elite 5-MS capillary column (5%
diphenyl-dimethylpolysiloxane; 0.25 mm
i.d.×30 m; film thickness, 0.25 µm) with
injections in the split mode and a split
ratio of 20. Helium was used as the carrier
gas at a flow rate of 1.0 mL/min. The
column temperature was maintained
initially at 60°C for 3 min, gradually
increased to 130°C at a rate of 4°C/min,
maintained at 130°C for 2 min, and finally
increased to 240°C at a rate of 20°C/min.
The injection port temperature was 240°C
and an ionization voltage of 70 eV was
applied with a mass range m/z of 20-550
amu. The separated components were
tentatively identified by matching the data
with electron ionisation-mass
spectroscopy (EI-MS) results of the
National Institute of Standards and
Technology (NIST), and the National
Bureau of Standards (NBS) mass spectral
library data. Quantitative determination
was based on peak area integration.
RESULTS AND DISCUSSION
Mineral content of herbs
The mineral contents of lemon
verbena and lemon thyme are
presented in Table 1. In lemon
verbena, the contents of cadmium
(Cd), chromium (Cr), copper (Cu),
iron (Fe), manganese (Mn),
phosphorus (P), and selenium (Se)
were 0.249, 1.498, 1.630, 16.41,
0.106, 0.734, and 5.241 mg kg-1,
respectively. In lemon thyme, the
contents of calcium (Ca), Cd, Cr, Cu,
Fe, magnesium (Mg), Mn, P, Se, and
zinc (Zn) were 8924, 0.275, 7.603,
4.584, 248.1, 2685, 15.17, 593.7,
0.219, and 1.803 mg kg-1,
respectively. dos Reis et al. (2010)

S. KIZIL, Ö. TONÇER
100
reported that, in L. alba, the mean
values of Ca, Mg, and potassium (K)
contents were 1,950, 2,856, and 2.335
mg 100 g-1 , respectively, and that the
contents of the microelements barium
(Ba), Zn, Cu, Fe, Mn, and nickel (Ni)
were 2.16, 2.95, 0.94, 11.2, 4.25, and
0.09 mg 100 g-1, respectively.
Table 1 - Microelement content in T. citriodorus and L. citriodora (mg kg-1)
Microelement T. citriodorus L. citriodora
Ca - 8924
Cd 0.249 0.275
Co - -
Cr 1.498 7.603
Cu 1.630 4.584
Fe 16.41 248.1
Mg - 2685
Mn 0.106 15.17
P 0.734 593.7
Se 5.241 0.219
Zn - 1.803
The metals Mn, Fe, Cu, and Zn,
and the non-metal Se are considered
to be trace elements because of their
essential, but very limited, presence in
human body. Deficiencies in any of
these microelements lead to health
problems that can be avoided by
maintaining sufficient levels. Lower
limits for these elements are 27.4 mg
kg-1 for Zn, 3.00 mg kg-1 for Cu, 2 mg
kg-1 for Mn, and 20 mg kg-1 for Fe
according to the permissible limits set
by the Food and Agriculture
Organization (FAO) and the World
Health Organization (WHO) (Ghani et
al., 2012). Shaw et al. (2004) reported
that the normal Cu content in plants
was 4-15 mg kg-1. Sharat Singh et al.
(2010) reported that the daily
microelement intake requirements for
Fe, Zn, Mn, Cu, Cr, and Se were 10-
15, 15, 2.5-5.0, 2-3, 0.05-0.2, and
0.05-0.2 mg per day, respectively.
These microelement requirements can
be met by consuming herbal teas.
Composition of essential oils
The chemical composition of
lemon verbena essential oil is
summarized in Table 2. The essential
oil content of lemon verbena plants
was 0.58%. Nazari et al. (2009)
reported that the essential oil content
of lemon verbena plants grown in Iran
was 0.8%, and Rode (2000) reported
that the essential oil content of dried
leaves was season-and harvest-
dependent and varied from 0.81 to
1.19%. We identified 34 compounds,
representing 97.64% of the total oil
composition of lemon verbena.
Limonene (30.33%), trans-citral
(17%), cis-citral (12.77%),
caryophyllene oxide (5.71%) and
geraniol acetate (4.02%) were the
major components of L. citriodora

ESSENTIAL OIL AND MICROELEMENT COMPOSITION OF LEMON VERBENA AND LEMON THYME
101
essential oil. Nazari et al. (2009)
identified 40 compounds in lemon
verbena essential oil, accounting for
96.17% of the oil. Of these
compounds, caryophyllene oxide
(13.6%), 1,8-cineole (12.5%), and
nerol (5.54%) were the major
components.
Table 2 - Essential oil composition of L. citriodora
Component RT* Content (%)
1-Octen-3-ol 7.254 0.50
6-Methyl-5-heptene-2-one 7.393 3.48
β-Myrcene 7.467 0.40
p-Cymene 8.604 0.86
D-Limonene 8.824 30.33
Terpin 8.963 0.79
cis-Ocimene 9.323 1.97
Linalool 11.200 1.37
4-Ethyl-3-isopropyl-4-methylcyclohexanol 11.340 0.33
Limonene oxide, cis- 12.315 0.38
Limonene oxide 12.469 0.76
1-Cyclohexene-1-acetaldehyde, α,2-dimethyl- 12.829 0.44
Citronellal 12.968 0.54
Cyclopentene, 1,4-dimethyl-5-(1-ethylethyl)- 13.599 1.17
Pinane, 2,3-epoxy- 13.936 0.33
Terpineol 14.465 0.40
cis-Carveol 15.308 0.56
cis-Citral 16.020 12.77
(S)-(+)-Carvone 16.152 0.62
Bergamiol 16.335 0.50
3-Carvomenthenone 16.489 0.69
trans-Citral 17.039 17.00
Thymol 17.736 1.70
Carvacrol 17.993 0.33
Neryl acetate 19.900 0.57
Copaene 20.355 0.42
Geraniol acetate 20.546 4.02
Caryophyllene 21.859 2.65
Humulene 23.252 1.07
α-Curcumene 24.235 1.78
Spathulenol 25.996 2.06
Caryophyllene oxide 26.069 5.71
tau-Cadinol 26.744 0.84
α-Cadinol 26.883 0.30
Total 97.64
Essential oil yield (%) 0.58
*retention time

S. KIZIL, Ö. TONÇER
102
The essential oil composition of
lemon verbena plants cultivated in
Iran included geranial, 1,8-cineole,
and limonene (Meshkatalsadat et al.,
2010). Agah and Najafian (2012) used
alternative drying methods in a study
of L. citriodora plants and determined
that the main oil constituents were
limonene (4.0%), 1,8-cineole (1.92%),
trans-ocimene (3.2%), neral (23.5%),
geranial (34.2%), (E)-caryophyllene
(3.2%), germacrene-D (5.5%),
bicyclogermacrene (4.1%), (E)-
nerolidol (1.8%) and caryophyllene
oxide (2.4%). Khani et al. (2012)
determined that lemon verbena
essential oil constituents included
citral (11.3%), limonene (10.6%),
neral (7.9%), 4-phenyl undecan-4-ol
(7.7%), α-curcumene (6.5%), α-cedrol
(4.5%) and caryophyllene oxide
(4.5%).
Argyropoulou et al. (2007)
reported that lemon verbena grown in
Greece contained mainly geranial,
neral, and limonene, and that the oil
composition differed at two
developmental stages of the plants. In
May, the main constituents were
geranial (38.7%), neral (24.5%) and
limonene (5.8%), which together
constituted 69% of the total essential
oil composition. At harvest in
September, the major constituents
were limonene (17.7%), geranial
(26.8%) and neral (21.8%),
representing 66.3% of the oil.
Velasco-Negueruela et al. (1993)
showed that the main components of
essential oils were α-thujone
(28.29%), carvone (7.40%), β-
caryophyllene (5.39%), germacrene-D
(5.16%), bicyclogermacrene (4.53%),
spathulenol (6.06%) and
caryophyllene oxide (7.03%) for
Lippia turbinate; α-thujone (68.94%)
and carvone (10.34%) for Lippia
polystachya; myrcenone (15.48%),
myrcene (7.92%), limonene (9%),
camphor (10.55%), (E)-tagetenone
(6.30%), trans-dihydrocarvone
(5.85%) and cis-dihydrocarvone
(16.65%) for Lippia junelliana;
camphor (16.20%), africanene
isomers (5.04%), lippifoli-1(6)-en-5-
one (16.70%) and undetermined
compounds (14.89%) for Lippia
integrifolia. Similarly, Malekirad et al.
(2011) also reported that limonene,
neral, geraniol, 1-octane-3-ol and
curcumene were predominant
components in lemon verbena plants,
grown in Iran.
The differences between the
results of our study and those of other
studies highlight the impact that
geographical and ecological factors
can have on the qualitative and
quantitative characteristics of the
essential oils produced. In addition,
other factors, such as the
developmental stage of the plant and
growing conditions, can influence the
essential oil composition
(Argyropoulou et al., 2007).
We determined that the essential
oil content of lemon thyme was 0.9%
and we identified 22 components
within lemon thyme essential oil that
together accounted for 85.11% of the
total oil composition (Table 3). The
major constituents included trans-
geraniol (30.07%), trans-citral
(15.06%), cis-citral (11.71%), and cis-

ESSENTIAL OIL AND MICROELEMENT COMPOSITION OF LEMON VERBENA AND LEMON THYME
103
geraniol (7.65%) (Table 3). Omidbaigi
et al. (2009) studied the effect of
various harvest times on the quality
and quantity of lemon thyme essential
oil and showed that the highest oil
yield (2.21%) was obtained at the
beginning of flowering, with geraniol
being the predominant (54.2-72.5%)
component. The highest geraniol
content (72.5%) in the essential oil
was measured before the flowering
stage and the lowest content (54.2 %)
was measured at the fruit-set stage.
The most abundant components in
lemon verbena oil were previously
reported to be geraniol (54.4%),
geranial (13.9%), neral (10.1%), nerol
(5.2%), 3-octanone (3.3%) and
borneol (3.2%) (Omidbaigi et al.,
2005). Stahl-Biskup and Holthuijzen
(1995) also reported that the main
component of lemon thyme oil was
geraniol (more than 60%), with a high
level maintained from July to
October; they also detected geranyl
acetate (1.0%), geranyl butyrate
(0.8%), nerol (2.8%) and citronellol
(0.3%).
Table 3 - Essential oil composition of T. citriodorus
Component RT* Content (%)
3-Thujene 5.626 0.25
Pinene 5.831 0.12
Camphene 6.293 1.65
1-Octen-3-ol 7.254 0.57
3-Octanone 7.459 1.90
β-Myrcene 7.467 0.17
3-Octanol 7.782 6.18
(+)-4-Carene 8.340 0.26
p-Cymene 8.626 1.18
D-Limonene 8.765 0.45
Borneol 13.665 1.89
3-Pinanone 13.834 0.26
Isogeraniol 13.951 0.94
cis-Geraniol 15.653 7.65
cis-Citral 16.078 11.71
trans-Geraniol 16.717 30.07
trans-Citral 17.127 15.06
Borneol acetate 17.523 0.62
Thymol 18.074 1.45
Caryophyllene 21.873 1.32
β-Bisabolene 24.881 0.71
Caryophyllene oxide 26.054 0.70
Total 85.11
Essential oil yield (%) 0.90
*retention time

S. KIZIL, Ö. TONÇER
104
The lemon-scented compounds
geranial and neral contributed 8.2%
and 5.5%, respectively, to the total oil
composition, and thymol (0.5%) was
found in remarkable quantities. The
oil of lemon thyme plants cultivated
in Hungary exhibited a geraniol and
carvacrol chemotype (Horváth et al.,
2006). The essential oil compositions
observed in these other studies were
similar to our results.
CONCLUSION
Lemon verbena and lemon
thyme are lemon-scented herbs whose
leaves are used as herbal medicines
and as flavouring herbs in the food
industry. Our results showed that
lemon verbena has a limonene
chemotype, while lemon thyme has a
geraniol chemotype, and that the
mineral contents of these herbs fall
below WHO permissible levels and
likely do not constitute a health
hazard for consumers. The data
obtained in this study provide a basis
for further studies to enhance the
selection of limonene and geraniol-
chemotype plants with higher yields
and suitable essential oil composition.
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