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Antifungal Activity of the Carrot Seed Oil and its Major Sesquiterpene
Compounds
Izabela Jasicka-Misiak
a,*
, Jacek Lipok
a
, Ewa M. Nowakowska
a
, Piotr P. Wieczorek
a
,
Piotr Młynarz
b
, and Paweł Kafarski
a
a
Institute of Chemistry, University of Opole, Oleska 48, 45-052 Opole, Poland.
Fax: +4877 444401. E-mail: izajm@uni.opole.pl
b
Institute of Organic Chemistry, Biochemistry & Biotechnology, Wroclaw University of
Technology, Wybrzeze Wyspianskiego 27, 50-370 Wroclaw, Poland
* Author for correspondence and reprint requests
Z. Naturforsch. 59 c, 791Ð796 (2004); received July 22/August 8, 2004
Carrot seed oil is the source of the carotane sesquiterpenes carotol, daucol and β-caryo-
phyllene. These sesquiterpenic allelochemicals were evaluated against Alternaria alternata
isolated from the surface of carrot seeds cultivar Perfekcja, a variety widely distributed in
horticultural practise in Poland. Alternaria alternata is one of the most popular phytotoxic
fungi infesting the carrot plant. The strongest antifungal activity was observed for the main
constituent of carrot seed oil, carotol, which inhibited the radial growth of fungi by 65% at
the following concentration.
Key words: Carrot Seeds Oil, Carotol, Daucol, Antifungal Activity
Introduction
Nowadays there is a clear tendency towards the
utilisation of natural products, especially allelo-
chemicals, as alternative compounds for pest and
plant disease control, safe for humans and envi-
ronment. Therefore, the search of new natural
products including plant extracts, which might sub-
stitute synthetic agrochemicals or contribute to the
development of new agents for pest control, seems
to be important. It is well recognised that among
other plant products essential oils, rich in terpe-
noids and non-terpenoid compounds, possess vari-
ous and interesting allelopathic properties. Their
insecticidal action against specific pests and fungi-
cidal action towards some important plant patho-
gens have been recently reviewed (Isman, 2000).
Over the past decade a large volume of data
documenting the defence abilities of various seeds
with a long period of dormancy were accumulated
(Halloin, 1983; Harman, 1983; Kremer et al., 1984;
Ceballos et al., 1998; Özer et al., 1999). Among
them antimicrobial activity of chemicals exuded
from seeds and acting on soil-rhizosphere inter-
face was reported (Helsper et al., 1994). Quite sur-
prisingly, there is little information about the role
and importance of allelochemicals, which are pri-
mary constituents of seeds. The question whether
these compounds might play any role during the
0939Ð5075/2004/1100Ð0791 $ 06.00 ”2004 Verlag der Zeitschrift für Naturforschung, Tübingen · http://www.znaturforsch.com ·
D
storage, period of dormancy or at the very begin-
ning of seedling development and emergency still
remains unanswered. The fungal infections might
be considered as the main factor influencing the
health of plants at these early stages of their
growth and development. Therefore, it is not sur-
prising that many of the sesquiterpenoid com-
pounds are known from their antifungal activity
against plant pathogenic fungi, including the most
popular Alternaria sp. (Alvarez-Castellano et al.,
2001; Skaltsa et al., 2000). For example the sesqui-
terpene fulvoferruginin shows strong activity
against Gram-positive bacteria and significant an-
tifungal activity towards Paecilomyces varioti. An-
other carotane sesquiterpene, rugosal A, isolated
from Rosa rugosa, which is accumulated in the leaf
trichomes, shows antifungal activity against Cla-
dosporium herbarum (Ghisalberti, 1994).
Large varieties of compounds synthesised in
carrot tissues are known also for their allelopathic
activity. These include asarones (Guerin and Städ-
ler, 1984; Jasicka-Misiak and Lipok, 2000), chlo-
rogenic acid (Cole et al., 1988) and trans-2-nonenal
(Guerin and Ryan, 1980). In previous reports we
described phytotoxic activity of carrot seed oil and
its main terpenoic components (Jasicka-Misiak
et al., 2002).
To the best of our knowledge, the chemical com-
position and in vivo antimicrobial activities of
792 I. Jasicka-Misiak et al. · Antifungal Activity of Sesquiterpenes
carrot seed oil were investigated several times
(Guerin and Reveillere, 1985; Dwivedi et al., 1991;
Kilibarda et al., 1996;, Friedman et al., 2002). Al-
though, the information about allelopathic activity
of terpenes at all is massively accumulated in the
literature, the biological role of carrot seed sesqui-
terpenes is still poorly defined, especially in the
context of the low sensitivity of carrot seeds to
fungal infections.
The structures and chemical properties of two
most specific carrot seed sesquiterpenes, carotol
and daucol, were described (Sykora et al., 1961;
Hashidoko et al., 1992; Platzer et al., 1987; Bülow
and König, 2000), but nothing could be traced in
the literature about their antifungal activity. The
limited knowledge concerning the biological activ-
ity of daucol and carotol is surprising if con-
sidering the fact that they are present in carrot
seed oil in high amounts. Moreover, the oil is rela-
tively cheap and commercially available therefore
it can be treated as a valuable source of antifun-
gal substances.
In this work the novel, improved procedure of
isolation of carotol and daucol is reported and the
antifungal activity of these compounds against Al-
ternaria alternata, the most popular phytotoxic
fungus, was examined.
Materials and Methods
Starting material
Carrot seed oil was purchased from Augustus
Oils Ltd., London. β-Caryophyllene was pur-
chased from Aldrich, Poland. The commercially
available fungicide Funaben T containing thiuram
(45%) and carbendazim (20%) was produced by
Chemical Corporation Organika-Azot s.a., Poland.
Seeds of Daucus carota L. var. Perfekcja, collected
in 2001, were purchased from Torseed Co.,
Torun, Poland.
Isolation of carotol and daucol
Carotol. A portion (10 g) of the carrot seed oil
was subjected to silica gel (Merck Kieselgel 60;
0.063Ð0.2 mm particle size; 650 ¥25 mm ID) col-
umn chromatography. The column was eluted with
CH
2
Cl
2
, followed by 1% MeOH in CH
2
Cl
2
and
eluates were collected as 62 ¥20 ml fractions.
Each fraction was analysed by TLC (plate 5553,
Merck; solvent system benzene/EtOAc, 19:1 v/v,
developed by spraying with 0.5% anise aldehyde
in MeOH, heating at 105 ∞C for visualisation), and
fractions 9Ð20 having one spot of R
f
0.86, charac-
teristic for carotol, were combined. The fractions
were evaporated to dryness (3.35 g) yielding a pale
yellow oil, which was identified by means of GC-
MS and
1
H NMR spectroscopy.
Daucol. It was obtained by a series of silica gel
column chromatographic steps. The first step was
the same as during carotol isolation. The fractions
were controlled by TLC, and fractions 46Ð55,
showing a similar spotting patterns zone (R
f
be-
tween 0 and 0.32), were combined. After evapora-
tion, the residue (0.19 g) was characterised by GC-
MS, showing the presence of 10 compounds. This
mixture was applied onto a silica gel column
(Merck Kieselgel 60; 0.063Ð0.2 mm particle size;
300 ¥15 mm ID). The column was eluted with
CH
2
Cl
2
/EtOAc (15:1 v/v). Eluates were collected
as 26 ¥20 ml subfractions, analysed by TLC, and
those containing daucol were combined (fractions
10Ð17). The obtained compound was recrystal-
lised from hexane at 4 ∞C for 48 h and analysed by
GC-MS and
1
H NMR spectroscopy.
Structural studies
The analysis of the essential oil was performed
using a Hewlett Packard 6890 gas chromatograph
equipped with a FID detector. The diethyl ether
solution (1 µl) was injected into a HP-1 capillary
column (30 m ¥0.32 mm bonded-phase fused sil-
ica). The initial oven temperature was maintained
at 60 ∞C for 2 min and then raised at 10 ∞C min
Ð1
to 280 ∞C. Helium was used as carrier gas. MS
analyses were performed on a quadrupole Hewlett
Packard 6897 instrument with ionisation at 70 eV.
The structure of the active compound was found
using a peak matching library search to published
standard mass spectra and by comparison with lit-
erature data.
The NMR experiments were carried out using
a Bruker DRX 300 MHz spectrometer. Chemical
shifts were referred to TMS (tetramethylsilane).
The proton and carbon assignments were per-
formed by means of COSY, TOCSY, HMQC,
DEPT-135 and HMQC-TOCSY experiments
using a spin lock time in the range 80Ð120 ms. The
TOCSY spectra were acquired with total spin-
locking time of 80 ms using the MLEV-17 mixing
sequence. In order to assign the carbon signal of
the daucol molecule the HMBC spectra were ad-
ditionally performed.
I. Jasicka-Misiak et al. · Antifungal Activity of Sesquiterpenes 793
Antifungal activity
Fungal bioassays in 9-cm Petri dishes were de-
signed to evaluate the influence of tested sub-
stances on mycelial growth of Alternaria alternata.
The mixtures of: carotol, caryophyllene and daucol
8:2:1 w/w/w (at the same weight ratio as it was
found in carrot seed oil and in carrot seeds); caro-
tol and daucol 8:1 w/w; carotol and caryophyllene
4:1 w/w; caryophyllene and daucol 2:1 w/w as well
as carrot seed oil were tested for antifungal activ-
ity. Appropriate amounts of above terpenoids
were mixed (before sterilization) with Czapek me-
dium to obtain the final concentration of 150 mg/l.
The commercially available fungicide Funaben T
was used as a control. The agar was allowed to
solidify and experiments were initiated by placing
6-mm fungal plugs taken from the growing mar-
gins of 9-day-old cultures, mycelial side down, on
Czapek medium. Plates were incubated at 24Ð
25 ∞C. Radial growth of the strain was recorded
daily, by taking the mean diameter of colonies
from each plate. The same experiments were car-
ried out for individual compounds: carotol, daucol
and caryophyllene. All the experiments were per-
formed four times, with four replications with four
pure Czapek medium controls.
Data analysis
The data were subjected to analysis of variance
to test the significance of all factors examined in
each experiment. F test was done to determine the
homogeneity of error variances among runs. Treat-
ment means were separated using Tukey’s HSD
test at a 5% significance level (Statgraphics
“
Plus 5, 2000).
Results and Discussion
Carrot seed oil composition
The chemical composition of the carrot seed oil
was determined by GC-MS analysis. The results
are presented in Table I as percent of the total MS
ion current. The compounds are listed according
to their elution order. Monoterpenes and sesqui-
terpenes represent the major components of car-
rot seed oil. Out of 40 compounds detected in the
chromatogram of the carrot seed oil 33 were iden-
tified. In our studies, only those components which
were present in the oil in amounts higher than
0.1% have been taken into consideration.
Table I. Levels (peak area percent) of major compo-
nents of carrot seed oil purchased from Augustus Oils
Ltd.
Component Carrot seed oil
RT
a
RA
b
(%)
α-Thujene 3.06 1.90
α-Pinene 3.20 3.94
Camphene 3.43 0.92
β-Pinene 3.46 1.90
β-Myrcene 3.65 1.44
α-Terpinene 3.97 1.43
o-Cymene 4.03 1.34
Limonene 4.12 1.75
γ-Terpinene 4.49 1.43
Terpinolene 5.54 0.63
Linalool 6.08 0.51
Pinen-4-ol 7.32 0.42
Terpinen-4-ol 8.16 0.22
3-Carene 8.60 0.83
Neryl acetate 8.69 1.06
Calarene 8.80 3.23
Zingibren 8.99 2.13
α-Farnesene 9.10 3.35
β-Caryophyllene 9.18 10.66
α-Cedrene 9.35 2.74
α-Himachalene 9.44 0.55
β-Cubebene 9.57 0.53
α-Longipinene 9.73 0.76
Aromadendrene 9.93 1.92
β-Farnesene 10.08 4.03
Levomenol 10.18 0.34
Vitamin A aldehyde 10.33 0.66
Isolimonene 10.56 3.24
Caryophyllene oxide 10.97 4.34
Carotol 11.22 38.85
χ-Cadinene 11.49 0.25
Daucol 11.57 2.00
Total 99.30
a
Retention time on HP-1 column in minutes.
b
Relative area (peak area relative to total peak area).
The main components of the oil were carotol
(38.8%) and β-caryophyllene (10.7%), accompa-
nied by caryophyllene oxide (4.3%) and a second
daucane sesquiterpene alcohol namely daucol
which is present in significant amounts (2.0%).
The other identified volatile components have
been reported previously as constituents of an-
other organs of carrot (Seifert and Buttery, 1978;
Buttery et al., 1979; Kjeldsen et al., 2001). All of
them, except the sesquiterpenic alcohols carotol
and daucol are well-known compounds isolated
from many other plant sources. Especially, β-ca-
ryophyllene is a widespread sesquiterpene. Caro-
tol, daucol and β-caryophyllene comprised 51.5%
of the oil.
794 I. Jasicka-Misiak et al. · Antifungal Activity of Sesquiterpenes
OH
1
23
5
6
7
8
9
10
11
13
14
15
4
12
a
OH
O
1
23
5
6
8
9
10
11
12
14
15
b
4
Fig. 1. Structures of carotol (a) and daucol (b).
Isolation of carotol and daucol
The previously described methods for isolation
of carotol and daucol are based on fractional dis-
tillation (Sykora et al., 1961; Hashidoko et al.,
1992). In our opinion column chromatography is a
faster and simpler method since carotol was ob-
tained from carrot seed oil by only one step by
means of silica gel column chromatography with
high efficiency (99%). Fractions with daucol were
provided by the same column, however, they re-
quired further purification by means of additional
silica gel column chromatography. These three
chromatographic steps resulted in the isolation of
daucol of 99% purity.
1
H NMR and
13
C NMR spectra of carotol and
daucol (Fig. 1) assigned using the set of NMR ex-
periments (see Materials and Methods) are sum-
marized in Tables II and III.( The chemical shifts
of proton and carbon peaks for the carotol mole-
Table II.
1
H and
13
C chemical shifts of carotol in chloro-
form (CDCl
3
).
Number of
1
H
a13
C
a1
H
13
C
carbon
with
its proton
1C 49.09 49.08
2CH
2
1.70/2.26 38.62 1.70/2.26 38.62
3CH 5.32 122.13 5.32 122.13
4C 138.60 138.59
5CH
2
2.08 29.45 2.08 29.45
6CH
2
1.94 34.45 1.63/1.94 34.41
7C 84.55 84.54
8CH 1.80 52.54 1.79 52.53
9CH
2
24.39 1.52/1.68 24.39
10CH
2
1.3 39.45 1.29/1.57 39.45
11CH
3
0.95 21.47 0.95 21.47
12CH
3
1.67 25.23 1.67 25.24
13CH 1.80 27.58 1.81 27.59
14CH
3
1.00 24.04 1.00 24.05
15CH
3
0.95 21.38 0.94 21.38
7C-OH 1.14 1.14
a
Bülow and König, 2000.
Table III.
1
H and
13
C chemical shifts of daucol in chloro-
form (CDCl
3
).
Number of
1
H
a1
H
13
C
carbon with
its proton
1C 45.15
2CH
2
1.28/1.68 1.28/1.68 40.09
3CH 3.72 3.74 71.70
4C 85.22
5CH
2
1.36/1.86 1.37/1.86 29.50
6CH
2
1.55/2.15 1.58/2.15 41.15
7C 91.63
8CH 1.50 1.50 52.40
9CH
2
1.70 1.71 26.20
10CH
2
1.25/1.30 1.24/1.28 32.90
11CH
3
1.06 1.06 22.42
12CH
3
1.36 1.36 23.45
13CH 1.77 1.78 31.51
14CH
3
0.81 0.82 21.79
15CH
3
1.06 1.06 22.93
a
Platzer et al., 1987.
cule are in good agreement with those reported in
the literature (Bülow and König, 2000; Platzer
et al., 1987; Hashidoko et al., 1992). The proton
chemical shifts of daucol are also in good consis-
tence with only one up to now published data
(Bülow and König, 2000), however, additional as-
signments for carbon atoms were performed (Ta-
ble III).
Antifungal activity
The antifungal activity of carrot seed terpenoids
was tested on strains isolated from non-disinfected
and untreated seeds. Seven strains of fungi belong-
ing to the Alternaria family and one strain of
Acremonium were isolated from the surface of
carrot seeds. Thus, Alternaria predominated
among all the identified genera of fungi. Because
the phytopathogenic activity of Alternaria towards
carrot plants is well documented they were chosen
for further experiments.
At the start, we tested the effect of crude carrot
seed oil and appropriate mixtures of carotol,
caryophyllene and daucol in different weight ra-
tios (see Materials and Methods) on the growth of
Alternaria alternata. The composition of the mix-
ture of the three terpenoids was set at the same
ratio as it was found in crude oil. For comparison
the additional tests with the commercially avail-
able fungicide Funaben T were also performed.
The obtained results are shown in Fig. 2a. Carrot
I. Jasicka-Misiak et al. · Antifungal Activity of Sesquiterpenes 795
Fig. 2. The effect of tested mixtures (a)
and poor substances (b) at 150 mg/l on
mycelial growth of Alternaria alternata
0
1
2
3
4
5
6
7
8
9
10
11
12345678910
control
seed oil
daucol
carotol
Funaben T
Cultivation time [d]
Colony diameter [cm]
0
1
2
3
4
5
6
7
8
9
10
11
12345678910
control
carotol;caryophyllene (2:1 w/w)
carotol;caryophyllene (4:1 w/w)
carotol;daucol (8:1 w/w)
carotol;caryophyllene;daucol (8:2:1 w/w/w)
Funaben T
a
b
on solid media.
seed oil exhibited moderate inhibitory effects on
mycelium radial growth of Alternaria alternata
(20% of inhibition). Mixtures containing only ca-
rotol exhibited strong inhibitory activity. This ac-
tivity increased with an increasing content of caro-
tol in individual mixtures. The highest inhibition
of the growth of pathogenic fungi was determined
for a carotol and daucol mixture (66%) in which
the content of carotol was the highest (90%).
The experiments with individual substances,
namely carotol, caryophyllene and daucol were
carried out to find out, whether the observed ac-
tivity derives from the action of carotol only or
from a synergetic nature. The kinetics of inhibition
of Alternaria alternata by these terpenoids used at
the concentration 150 mgl/l in Czapek medium is
shown in Fig. 2b. It is clearly seen that these com-
pounds started to influence the fungal growth after
the third day of incubation (see the standard devi-
ation bars) and the differences in their action had
significantly grown with time. Carotol significantly
inhibited the growth of the fungi and reduced the
colony radial size by 65% at the 9
th
day of the
experiment. Quite different effects were observed
for daucol (second specific sesquiterpene alcohol
of the oil) where slight stimulation of the develop-
ment of Alternaria alternata was observed. Wide-
spread in various plants the sesquiterpene β-ca-
ryophyllene failed to have any effect. Therefore, it
can be concluded that carotol is the main agent
attributed for antifungal activity of carrot seeds.
The activity of carotol is nearly as strong as of the
commercially abailable fungicide Funaben T
(85%).
796 I. Jasicka-Misiak et al. · Antifungal Activity of Sesquiterpenes
Acknowledgements
This research was supported by Polish State
Committee for Scientific Research (Komitet Ba-
dan
´Naukowych) grants PBZ KBN Ð060/T09/
2001/37. Piotr Młynarz wishes to thank The Foun-
dations for Polish Science for scholarship.
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