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Studies on Betula Essential Oils

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Essential oils were obtained from leaf, branch and buds of Betula species: B. pendula Roth, B. browicziana A.Güner, B. litwinowii Doluch., B. recurvata V. Vassil., and B. medwediewii Regel naturally growing in various parts of Turkey. Also buds of the common birch B. pendula essential oil from Germany and two species native to Finland namely, Betula pubescens ssp. czerepanovii (Orlova) Hämet-Ahti and Betula pubescens ssp. pubescens Erhr. were investigated. Betula essential oils were obtained by different distillation techniques such as hydrodistillation, microdistillation and Likens-Nickerson simultaneous distillation-extraction method (SDE). The resulting volatile compositions were elucidated by gas chromatography (GC) and gas chromatography-mass spectrometry (GC-MS) systems. Known and new sesquiterpenes were isolated from Betula essential oils using column chromatographic techniques. Structure determination of each isolated compound was carried out using 1D and 2D NMR spectroscopic techniques supported by MS, UV and GC FITR. Biological activities were determined both for essential oils and pure compounds isolated from the oils of Betula species. Antifungal, antibacterial and antioxidant activity results were carried out using various in vitro techniques.
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Issue in Honor of Prof. Atta-ur-Rahman ARKIVOC 2007 (vii) 335-348
ISSN 1424-6376 Page 335 ©ARKAT USA, Inc.
Studies on Betula essential oils
K. Hüsnü Can Başer* and Betül Demirci
Department of Pharmacognosy, Faculty of Pharmacy, Anadolu University, 26470-Eskişehir,
Turkey
E-mail: khcbaser@anadolu.edu.tr
Dedicated to Professor Atta-Ur-Rahman on the occasion of his 65th birthday
Abstract
Essential oils were obtained from leaf, branch and buds of Betula species: B. pendula Roth, B.
browicziana A.Güner, B. litwinowii Doluch., B. recurvata V. Vassil., and B. medwediewii Regel
naturally growing in various parts of Turkey. Also buds of the common birch B. pendula
essential oil from Germany and two species native to Finland namely, Betula pubescens ssp.
czerepanovii (Orlova) Hämet-Ahti and Betula pubescens ssp. pubescens Erhr. were investigated.
Betula essential oils were obtained by different distillation techniques such as hydrodistillation,
microdistillation and Likens-Nickerson simultaneous distillation-extraction method (SDE). The
resulting volatile compositions were elucidated by gas chromatography (GC) and gas
chromatography-mass spectrometry (GC-MS) systems.
Known and new sesquiterpenes were isolated from Betula essential oils using column
chromatographic techniques. Structure determination of each isolated compound was carried out
using 1D and 2D NMR spectroscopic techniques supported by MS, UV and GC FITR.
Biological activities were determined both for essential oils and pure compounds isolated from
the oils of Betula species. Antifungal, antibacterial and antioxidant activity results were carried
out using various in vitro techniques.
Keywords: Betulaceae, Betula species, Birch tree, essential oil, sesquiterpenes, caryophyllene,
chromato-spectral techniques, biological activity
Introduction
Well-known as birch tree, the genus Betula of the family Betulaceae, has a wide distribution in
the northern hemisphere from Canada to Japan.1 Five Betula species, namely B. browicziana A.
Güner, B. litwinowii Doluch., B. medwediewii Regel, B. pendula Roth and B. recurvata V. Vassil
are naturally growing in eastern and northern Turkey, at high altitudes. Only B. browicziana is
endemic to Turkey.2,3
The Birch tree has a long history of medicinal use in different countries and cultures to cure
skin diseases especially eczema, infections, inflammations, rheumatism and urinary disorders.
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Betula bud oil is also widely used in cosmetic products as a tonic and antiseptic mainly in hair
products.4-7
Birch bark contains betulin, betulinol and a betuloside. The young leaves are rich in saponins
and contain a diuretic flavonoid derivative (hyperoside), sesquiterpenes and tannins. The buds
are rich in volatile oil. Birch tar contains creosol and guaiacol.5,8
The essential oils obtained from Betula species have been the subject of many
investigations.7-12 Betulenol, the main component of the oil, was isolated and reported from
Betula buds and named first as betulol by Soden and Elze in 1905. Its structure was tentatively
elucidated as a bicyclic primary sesquiterpene alcohol. Further investigations on this molecule
were conducted by Triebs and other researchers as compiled in a work of Guenther.5 Afterwards
Treibs and Lossner reported α- and β-betulenol, their acetates and α-betulenal by means of
synthesis to support the chemical structures present in the essential oil of Betula lenta.8 In
contrast, Holub reported the occurrence of α- and β-betulenol, as well as α-betulenol acetate
with different structures as the previous investigators, also isolated from Betula species.9 Dhar et
al. reviewed the chemistry of the birch tree including the essential oil which appeared to support
Holubs' previous work.10 Hiltunen and co-workers reconfirmed by means of chemical reactions
and gas chromatography / mass spectrometry (GC - MS), the occurrence of the main compounds
as α- and β-betulenol and their relevant acetates in the bud oil of B. pubescens Ehrh., supporting
Treibs’ work.11
Essential oil components of B. pendula were analyzed by Stepen and co-workers using GC
where the main components were identified as α-betulenol acetate, caryophyllene and
derivatives including low amounts of α- and β-betulenol.12 Kaneko et al. reported betulenols
and their acetates in the essential oils isolated from the buds of nineteen Betula species.7 Studies
on the essential oils and sesquiterpenes of Betula species growing in Turkey were subject to
several studies by our group.13-18
This present work covers the essential oil chemistry as well as biological activities of the
main components isolated from various Betula species investigated by our group.
Results and Discussion
Caryophyllene and its derivatives have been of special interest in the field of natural products
chemistry and subjected to many detailed works and reviews.19-22 There have been many
conflicts and disagreements concerning absolute configurations and structures of caryophyllene
derivatives isolated from natural sources.7-9,23
The buds of B. pendula, B. litwinowii and B. medwediewii collected from various parts of
Turkey were hydrodistilled while B. browicziana and B. recurvata buds were subjected to
simultaneous distillation-extraction method (SDE) using a Likens-Nickerson apparatus due to
limited plant material. The bud oils were analysed by GC-MS. The main component was isolated
by Medium Pressure Liquid Chromatography (MPLC) in high purity.13,16 Literature search and
comparison with spectral data23 confirmed the identity of this compound as 14-hydroxy-β-
caryophyllene (1), which was found 20.5-37.5% in all investigated oils.
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In the light of the recent accumulated data, we propose that 14-hydroxy-β-caryophyllene is
synonymous with α-betulenol formerly isolated by Treibs from the bud essential oil of B. lenta 8.
The isolation of 14-hydroxy-β-caryophyllene (1) was also reported by Macleod24 from
Pterocaulon serrulatum (Montr.) Guillaumin, an Australian plant, supporting the previously
reported data.23,25
We acetylated 1 to form 14-acetoxy-β-caryophyllene (1a),13 which was also shown to be
naturally present in Betula bud essential oils (0.1-0.8%) by GC-MS (Scheme 1). Consequently,
we suggest that 14-acetoxy-β-caryophyllene (1a) is synonymous with α-betulenol acetate, which
was reported from B. lenta essential oil earlier.8
(CH
3
CO)
2
O
Pyridine, 60
0
C
H
H
1
H
H
1a
OH OAc
Scheme 1. Acetylation of 14-hydroxy-β-caryophyllene (1).
β-Betulenal (2) which was isolated by MPLC from Betula essential oils was also
synthesized. 13 β-caryophyllene (3) was treated with SeO2, resulting in the formation of β-
betulenal (2), 14-hydroxy-isocaryophyllene (4), and isocaryophyllene (5), as seen in Scheme 2.
Compound 2 and 4 were isolated individually from the reaction mixture followed by structures
confirmation by 1H and 13C NMR. This information supported that 14-hydroxy-isocaryophyllene
(4) is synonymous with β-betulenol and β-betulenal (2) with isocaryophyllen-14-al, when
compared with previous investigations.8 To ensure the proposal, 2 was subjected to a mild
reduction with NaBH4, resulting in β-betulenol (4). These compounds were also detected in the
Betula bud essential oils by GC-MS. Content of β-betulenol and β-betulenal, in the oils of
investigated Betula species were found from trace to 1.2% and 2.0-5.2%, respectively (Table 1).
H
H
3
H
H
2 R= CHO
4 R= CH
2
OH
5 R= CH
3
R
SeO
2
EtOH
Scheme 2. Oxidation of β-caryophyllene (3).
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Table 1. Main components of the different parts of Betula species growing in Turkey
RRI Compound Betula pendula
%
Betula browicziana
%
Betula litwinowii
%
Betula
medwediewii
%
Betula recurvata
%
Br L B Br L B Br L B Br L B Br L B
1093 Hexanal 0.1 0.1 tr 0.1 0.1 tr - - - 0.1 0.5 tr - 0.1 -
1225 (Z)-3-Hexenal tr 0.2 tr - 0.4 tr - tr - - 5.8 - - 0.4 -
1360 Hexanol 0.1 0.1 tr 0.1 0.1 tr - 0.2 - - 1.4 - - 0.2 -
1400 Nonanal 0.2 0.1 tr 0.2 0.6 0.1 - 0.1 - 0.2 1.8 0.1 tr 0.2 -
1412 (E)-2-Hexenol - - - - - - - - - - 0.7 - - 0.1 -
1553 Linalool 0.4 0.1 tr 0.3 0.5 0.1 0.5 1.0 - 0.3 2.8 tr 0.2 0.2 -
1612 β-Caryophyllene (3) 2.9 1.4 3.9 2.4 0.3 4.9 0.8 1.1 1.3 0.1 0.4 1.2 0.2 1.3 3.2
1687 α-Humulene 4.3 2.0 6.8 3.8 0.3 3.7 0.8 0.7 1.6 0.2 0.2 2.3 0.3 1.7 5.6
1706 α-Terpineol 0.1 tr - 0.1 0.1 - 0.2 0.3 - 0.1 0.5 - tr 0.1 -
1758 (E,E)-α-Farnesene - - - - - tr 0.2 0.6 - - 1.9 tr tr 0.1 -
1772 Citronellol 0.2 tr tr 0.1 0.1 tr 0.3 0.7 - 0.6 - 0.1 0.1 0.1 -
1798 Methyl salicylate tr - - - - - - - - 67.8 49.8 0.3 - - -
1802 Cumin aldehyde - - - - 0.8 - - - - - - tr - - -
1804 Myrtenol 0.2 - - 0.7 - - - - - - - - tr tr -
1834 ethyl salicylate - - - - - - - - - 4.8 0.2 - - - -
1857 Geraniol 0.3 0.1 0.1 0.2 1.1 tr 0.4 2.0 tr 3.4 1.8 0.4 0.1 0.6 tr
1958 (E)-β-Ionone - 0.6 - 0.1 0.3 - - 0.2 - 0.2 1.0 - - tr -
2008 Caryophyllene oxide 4.0 4.3 5.3 3.9 2.3 6.1 2.3 3.1 3.2 0.4 0.5 2.6 1.6 2.9 1.7
2020 des-4-Methyl-
caryophyll-8(14)-en-5-
one (10)
5.3 4.7 5.1 6.9 10.2 5.2 3.1 5.7 6.0 2.2 0.8 7.8 4.2 6.9 3.9
2041 Pentadecanal - - - - - - - - - 0.5 0.2 0.3 - - -
2045 Humulene epoxide-I 0.5 0.3 0.6 0.6 0.2 0.3 tr 0.1 0.2 - - 0.2 0.1 0.2 0.2
2071 Humulene epoxide-II 4.9 4.8 6.9 3.9 2.4 4.2 1.4 1.5 3.3 0.4 0.4 3.1 1.3 2.6 2.4
2092 4,5-Dihydro-β-
caryophyllene-14-al (9)
1.5 2.3 1.5 0.8 1.1 1.3 0.2 0.6 2.2 0.3 0.1 2.7 0.3 2.2 0.8
2100 Heneicosane 0.6 0.1 0.4 - - tr 0.3 0.3 - 0.1 - 0.4 0.4 - -
2186 Eugenol 1.7 0.2 0.2 0.9 0.2 0.3 - - 0.1 1.0 0.9 0.1 - 0.6 tr
2193 β-Betulenal (2) 7.6 4.7 4.0 11.1 13.9 5.2 5.5 7.3 3.3 0.7 0.8 2.7 4.4 5.2 2.0
2200 Docosane 0.1 - - - - - 0.2 1.1 - - - - - - -
2239 Carvacrol - tr - 2.6 2.5 0.1 0.2 0.1 tr 2.2 0.6 1.0 0.2 0.1 tr
2272 14-Acetoxy-β-
caryophyllene
(=α-Betulenol acetate)
(1a)
0.6 0.6 0.8 1.2 0.5 0.8 0.7 1.0 0.2 tr - 0.1 3.7 2.3 0.5
2282 14-Acetoxy-4,5-dihydro-
β-caryophyllene (8a)
0.3 0.2 0.4 - 0.2 0.3 0.3 0.4 0.2 0.1 - 0.3 0.5 0.3 0.3
2300 Tricosane 1.0 - - 0.3 - - 3.0 1.1 - 0.2 0.1 0.9 2.6 - -
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2316 Caryophylla-
4(14),8(15)-dien-5β-ol
(=Caryophylladienol I)
0.4 0.6 0.4 0.5 0.8 1.1 0.4 0.7 0.4 - 0.4 0.2 0.3 0.7 0.2
2324 Caryophylla-
4(14),8(15)-dien-5α-ol
(=Caryophylladienol II)
1.4 2.1 1.7 1.5 1.8 2.8 1.5 2.6 0.9 tr - 0.6 1.0 2.1 0.6
2329 14-Acetoxy-α-
humulene
0.3 0.2 0.3 - - - 0.2 0.2 0.1 - - 0.1 0.2 0.1 0.1
2346 6-
Hydroxycaryophyllene
(14)
1.0 1.6 1.4 0.5 0.3 2.0 2.3 3.7 0.9 - - 0.9 0.3 1.1 2.1
2357 14-Hydroxy-β-
caryophyllene (=α-
Betulenol) (1)
19.8 29.3 25.3 18.0 12.7 28.2 14.4 13.2 21.9 1.8 3.5 20.5 8.2 20.8 37.5
2384 Hexadecanol - - - - 1.3 - - 0.3 - - 0.4 - - 0.5 -
2393 14-Hydroxy-
isocaryophyllene (=β-
Betulenol) (4)
0.9 1.3 1.2 1.3 1.1 1.0 - 0.6 0.6 0.2 0.1 0.8 0.4 0.5 tr
2400 Tetracosane - - - - - - 0.7 - - - - - 0.2 - -
2415 14-Hydroxy-4,5-
dihydro-β-
caryophyllene (8)
13.4 21.4 17.2 14.3 24.8 16.0 19.1 18.5 36.8 4.2 3.7 27.6
22.7 25.2 23.8
2478 14-Hydroxy-α-
humulene
1.0 1.4 1.7 1.2 0.4 1.1 0.6 0.7 3.3 0.2 - 4.9 0.5 1.4 3.5
2500 Pentacosane 5.3 1.3 0.5 1.3 2.0 - 13.6 3.6 0.4 0.2 1.2 1.6 13.3 1.2 0.2
2609 14-Hydroxy-4,5-epoxy-
β-caryophyllene (
ββ
)
(7)
- 0.2 0.2 tr - 0.1 - - - - - - - 0.1 -
2617 14-Acetoxy-4,5-epoxy-
β-caryophyllene (
βα
)
(6a)
- - tr tr - - - - - - - - - 0.2 -
2622 Phytol 0.1 0.2 tr 0.1 0.2 - 0.1 0.6 - - 1.6 0.1 0.7 0.4 -
2663 14-Hydroxy-4,5-epoxy-
β-caryophyllene (
βα
)
(6)
0.2 0.9 1.3 0.3 0.2 0.4 - 0.3 0.9 - 0.1 0.3 - 0.5 0.7
2700 Heptacosane 3.2 0.2 0.3 0.6 0.8 - 3.0 2.4 - 0.1 1.4 1.7 8.6 1.0 -
2931 Hexadecanoic acid 0.4 0.2 0.1 1.0 0.4 - 0.9 0.5 - 0.1 3.1 0.1 1.0 0.1 -
Br: Branch, L: Leaf, B: Bud
RRI Relative retention indices calculated against n-alkanes
% calculated from TIC data
tr Trace (< 0.1 %)
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Manns and Hartmann reported (4E)-isocaryophyllen-14-al (=β-betulenal) in Cunila spicata
Benth. (Lamiacea).26 Barrero et al.27 and Hiede et al.28 reported the presence of betulenal in
Juniperus oxycedrus and J. virginiana essential oils without its configuration. Kaiser and
Lamparsky29 assigned the structure of the aldehyde, formed in the reaction mixture by direct
oxidation of caryophyllene with SeO2, as caryophyllen-14-al (=α-betulenal), which was also
detected in lavender oil.
With the same intention as above we acetylated 14-hydroxy-isocaryophyllene (4), resulting
in the formation of 14-acetoxy-isocaryophyllene (=β-betulenol acetate) (4a). However, the
acetate 4a was not detected in any Betula essential oils investigated in this study (Scheme 3).
H
H
4
CH
2
OH H
H
4a
CH
2
OAc
(CH
3
CO)
2
O
Pyridine, 60
0
C
Scheme 3. Acetylation of 14-hydroxy-isocaryophyllene (4).
Furthermore, 14-hydroxy-β-caryophyllene (1) was epoxidized by m-CPBA resulting in the
formation of the two synthetic diastereomeric epoxides namely, 14-hydroxy-4,5-epoxy-β-
caryophyllene (
βα
) (6) and 14-hydroxy-4,5-epoxy-β-caryophyllene (
ββ
) (7), as shown in
Scheme 4.16 These compounds were shown to be present in the investigated Betula essential oils
(Table 1). 14-Hydroxy-4,5-epoxy-β-caryophyllene (
βα
) (6) was also obtained from the bud
essential oil of B. pendula by MPLC. The acetate of this compound (6a) was shown to be present
in the composition of the investigated Betula essential oils. The acetate of
ββ
-
form (7a) was also
found in essential oil of B. recurvata leaves in trace amounts (Table 1).
H
H
1
OH H
H
O
R
6 R= CH
2
OH
6a R= CH
2
OAc
H
H
O
R
7 R= CH
2
OH
7a R= CH
2
OAc
m-CPBA
MeOH, 0
0
C
Scheme 4. Epoxidation of 14-hydroxy-β-caryophyllene (1).
In vitro antimicrobial activity evaluation against selected human pathogens Escherichia coli,
Staphylococcus aureus, Micrococcus luteus, Pseudomonas aeruginosa, Bacillus cereus and the
fungus Candida glabrata using 14-hydroxy-β-caryophyllene (1), 14-acetoxy-β-caryophyllene
(1a), β-betulenal (2), β-caryophyllene (3), and 14-hydroxy-isocaryophyllene (4) were conducted.
Chloramphenicol was used as reference and moderate activities were observed against Gram
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(+)/(-) bacteria. Ketoconazole was used as antifungal reference against C. glabrata, where also
moderate activity was observed. Antibacterial activity was shown against Streptococcus nutans,
S. aureus and E. coli for caryophylla-4,8(13)-dien-6-ol, caryophylla-4,8(13)-dien-6-one,
caryophylla-4,7-dien-6-one and caryophylla-3,8(13)-dien-5,6-diol isolated from B. pubescens,
activities of which were said to be patented.30 Other antimicrobial investigations using different
extracts of various Betula species have been conducted.31-34 Recently, 14-hydroxy-β-
caryophyllene (1) was reported to have antibacterial activity against Bacillus subtilis and
Escherichia coli.24
Our research into Betula species growing in Turkey has resulted in the isolation of new
caryophyllene derivatives namely; 14-hydroxy-4,5-dihydro-β-caryophyllene (8), 4,5-dihydro-β-
caryophyllene-14-al (9), and des-4-methyl-caryophyll-8(14)-en-5-one (10) from B. litwinowii.15
14-Acetoxy-4,5-dihydro-β-caryophyllene (8a) was prepared from 14-hydroxy-4,5-dihydro-β-
caryophyllene (8) (Figure 1). 14-Acetoxy-4,5-dihydro-β-caryophyllene (8a) was also identified
by GC-MS and retention index data to be identical to that present in the Betula essential oils
(Table 1).
R
H
H
8 R= CH2OH
8a R= CH2OAc
CHO
H
H
9
H
H
10
O
Figure 1. Isolated and semi-synthetic new compunds from B. litwinowii.
14-hydroxy-4,5-dihydro-β-caryophyllene (8) induced 100% inhibition of the plant
pathogenic fungi Cephalosporium aphidicola and Rhizoctonia cerealis at 200
µ
g/mL. This
compound was also as active as the antibacterial standard chloramphenicol against Bacillus
cereus, with a MIC value of 125 µg/mL, but was less active against Escherichia coli,
Micrococcus luteus, Staphylococcus aureus, and Pseudomonas aeruginosa. Same compound
displayed moderate antifungal activity against Candida glabrata, having a MIC value of 125
µ
g/mL when compared to ketoconazole (62.5
µ
g/mL).15
The leaves of five Betula species growing in Turkey, were hydrodistilled and the oil
compositions were investigated by GC-MS. 14-Hydroxy-β-caryophyllene (1) was found as the
main constituents (29.3%) in the oil of B. pendula. 14-Hydroxy-4,5-dihydro-β-caryophyllene (8)
was identified as the main constituents in the oils of B. recurvata (25.%), B. browicziana
(24.8%) and B. litwinowii (18.5%). Interestingly, in the oil of B. medwediewii, methyl salicylate
(49.8%) was the major constituent.14
14-Hydroxy-β-caryophyllene (1) was found as main compound in the hydrodistilled branch
oil of B. pendula and B. browicziana (19.8% and 18.0%, respectively). 14-Hydroxy-4,5-dihydro-
β-caryophyllene (8) was characterized as the main component B. recurvata and B. litwinowii
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branch oils (22.7 and 19.1%, respectively). Methyl salicylate (67.7%) was identified as a major
compound in the oil of B. medwediewii (Table 1).
Various phytopathogenic fungi were evaluated by agar tube dilution method35 to test the
antifungal activities of the leaf essential oils of B. pendula, B. browicziana, B. medwediewii, B.
recurvata and B. litwinowii at 400
µ
g/mL concentration. Cephalosporium aphidicola,
Drechslera sorokiniana, Fusarium solani, Rhizoctonia cerealis, were inhibited, whereas weak
activity or no inhibition was observed against Aspergillus quadrilieneatus, A. flavus, Gibberella
fujikuroi, Trichoderma harzianum and Trichothecium roseum.14 Previous studies demonstrated
the antifungal activity of some Betula species; B. alba 36, B. lenta37, B. nigra38, B. papyrifera39
and B. plathyphylla var. japonica.40
In the course of our research into Betula species, we isolated essential oils from the buds of
Betula pubescens ssp. pubescens and B. pubescens ssp. czerepanovii naturaly growing in Finland
which were analyzed both by GC and GC-MS. 14-Acetoxy-β-caryophyllene (1a) was
determined as the main component in both oils (32.5 and 30.0%, respectively). The essential oil
was subjected to column chromatography and a bicyclic aldehyde; birkenal (11) and a tricyclic
lactone; hushinone (12) were isolated as new compounds. Birkenal (11) was subjected to a mild
reduction with NaBH4 to result in birkenol (13). This compound was shown to be naturally
present in both essential oils (0.4-0.6%) with the aid of GC-MS (Table 2). The acetate of this
alcohol; birkenyl acetate (13a) was shown to be naturally present at low concentrations (0.1%) in
both essential oils investigated, as a new natural compound. 6-Hydroxycaryophyllene (14) was
also isolated from the oils. Acetylation of this compound resulted in the formation of 6-
acetoxycaryophyllene (14a) (Figure 2). The new acetate was also detected in the essential oils
and identified as such by co-elution by means of TLC and GC-MS.17 Recently, Domrachev and
Tkachev assigned the absolute configuration of birkenal by chemical correlation with known
caryophyllene-type derivatives.41
The air-dried buds were hydrodistilled for 3 h using a Clevenger-type apparatus to yield
5.0% (A) and 7.8% (B) of essential oils on a dry-weight basis.
The antioxidant activities of the essential oils from both species and the isolated pure
compounds namely; birkenal (11), hushinone (12), birkenol (13), and 6-hydroxycaryophyllene
(14) were assessed by measuring their ability to scavenge 1,1-diphenyl-2-picrylhydrazyl radicals
(DPPH). The test was performed on the samples at concentrations of 0.5 and 1.0 mg/mL but
scavenging activity of the radicals was not determined.17
Other recent work of our group on volatiles of the buds of B. pendula obtained by
hydrodistillation and microdistillation collected from Germany was reported. The volatiles were
analyzed both by GC and GC-MS systems. α-Copaene (12% and 10%), germacrene D (11% and
18%) and δ-cadinene (11% and 15%) were identified as the main constituents in the
hydrodistilled and microdistilled samples, respectively. In this study, the essential oil profile of
B. pendula obtained from the buds (Table 3) was quite different from those of previous
investigations and results.13,14,16 Kaneko et al.7 had reported δ-cadinene (9.6%) as the main
constituent of B. pendula from Japan. However, in other previous studies betulenols were found
to be the major constituents in the volatile oil of B. pendula.13,14, 16, 42
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Table 2. Essential oil compositions the buds of B. pubescens ssp. pubescens (A) and B.
pubescens ssp. czerepanovii (B)
RRI Relative retention indices calculated against n-alkanes
%: calculated from FID data
tr: trace (< 0.1 %)
H
H
11 R= CHO
13 R= CH
2
OH
13a R= CH
2
OAc
R
H
H
O
O
12
H
H
14 R= OH
14a R= CH
2
OAc
R
Figure 2. Isolated and semi-synthetic compounds from Betula pubescens.
RRI Compound A (%) B (%)
1612 β-Caryophyllene (3) 0.3 0.7
1823 Birkenal (11) 11.7 10.8
2008 Caryophyllene oxide 3.1 3.5
2009 Birkenyl acetate (13a) 0.1 0.1
2071 Humulene epoxide II 0.4 0.5
2100 Heneicosane 1.3 0.4
2149 Birkenol (13) 0.4 0.6
2193 β-Betulenal (2) 1.1 1.7
2209 Hushinone (12) 0.7 0.2
2210 6-Acetoxycaryophyllene (14a) 5.0 1.0
2272 14-Acetoxy-β-caryophyllene (1a) 32.5 30.0
2300 Tricosane 1.7 2.6
2316 Caryophylla-2(12),6(13)-dien-5β-ol
(=Caryophylladienol I)
1.2 1.3
2324 Caryophylla-2(12),6(13)-dien-5α-ol
(=Caryophylladienol II)
5.2 5.8
2329 14-Acetoxy-α-humulene 1.2 0.7
2346 6-Hydroxycaryophyllene (14) 11.7 15.1
2357 14-Hydroxy-β-caryophyllene (1) 1.7 3.5
2617 14-Acetoxy-4,5-epoxy-β-caryophyllene (
βα
) (6a) 1.3 1.8
2663 14-Hydroxy-4,5-epoxy-β-caryophyllene (
βα
) (6) - 0.2
Issue in Honor of Prof. Atta-ur-Rahman ARKIVOC 2007 (vii) 335-348
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Conclusions
Betula species display an important resource for sesquiterpenes in particular for caryophyllene
derivatives. Their biological activity is also worthwhile to investigate as in in vitro pre-screens
we have observed antimicrobial activity against various human and plant pathogens. Another
interesting aspect of sesquiterpenes and caryophyllenes is the potential use in flavour and
fragrance industries, however, the mentioned secondary metabolites need to be investigated
further from this aspect.
Experimental Section
Plant material. Leaf, branch and buds of B. pendula, B. browicziana, B. litwinowii, B. recurvata
and B. medwediewii were collected from different localities in North Eastern region of Turkey.
Voucher specimens are kept at the Herbarium of the Faculty of Pharmacy of Anadolu University
in Eskişehir, Turkey (ESSE). Detailed information on the plant materials used are given in Table
4. Buds of B. pubescens ssp. czerepanovii and B. pubescens ssp. pubescens were collected in
April 2002 from the Botanical Garden of the University of Turku (SW Finland). Voucher
specimens of the buds have been deposited in the Turku University Herbarium under numbers
TUR 573172 and TUR 573171, respectively. Buds of B. pendula growing in Germany, were
collected from Maxhütte, Regensburg in April 2002.
The plant materials were either hydrodistilled using a Clevenger type apparatus or were
subjected to Likens-Nickerson simultaneous distillation-extraction (SDE) method and
Microdistillation method when the plant material amounts were insufficient. The essential oils
were analysed by GC and GC-MS.
Isolation of the essential oils
Hydrodistillation. The plant materials were subjected to hydrodistillation for 3 h using a
Clevenger-type apparatus to produce the essential oils. The percentage (%) yields were
calculated on dry weight basis after drying over anhydrous Na2SO4.
Likens-Nickerson distillation-extraction method. B. browicziana and B. recurvata (1.0 g of
buds) were subjected to SDE for 1 hour using a Likens-Nickerson apparatus with 1 ml of n-
hexane as solvent.
Microdistillation. The plant material (~200 mg) was placed in the sample vial of the
MicroDistiller® (Eppendorf, Germany) system together with 10 ml of distilled water. NaCl (2.5
g) and water (0.5 ml) were added into the collection vial to break any possible emulsion
formation. n-Hexane (300 µl) was also added into the collecting vial to trap the volatile
components. The sample vial was heated to 100ºC at a rate of 20ºC/min and then kept at 100ºC
for 15 min. It was then heated to 112ºC at a rate of 20ºC/min and kept at this temperature for 35
min. Later, the sample was subjected to post-run for 2 min under the same conditions. The
collecting vial was cooled to –5ºC during the distillation. After the distillation was completed the
n-hexane-trapped volatiles were analyzed by both by GC and GC-MS.
Issue in Honor of Prof. Atta-ur-Rahman ARKIVOC 2007 (vii) 335-348
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Table 3. Main components of Betula pendula buds growing in Germany
RRI Compound Hydrodistillation Microdistillation
1400 Nonanal 0.9 tr
1466 α-Cubebene 0.8 0.5
1493 α-Ylangene 1.1 0.7
1497 α-Copaene 11.8 9.6
1549 β-Cubebene 0.7 0.5
1589 β-Ylangene 1.3 0.4
1597
β-Copaene 1.0 0.5
1612 β-Caryophyllene (3) 3.4 3.2
1617 6,9-Guaiadiene 2.4 1.9
1628 Aromadendrene 0.6 0.3
1661 Alloaromadendrene 2.2 2.2
1677 epi-Zonarene 0.6 0.6
1687 α-Humulene 2.9 3.0
1704 γ-Muurolene 2.6 3.0
1726 Germacrene D 11.4 18.0
1740 α-Muurolene 2.0 2.5
1773 δ-Cadinene 10.8 15.3
1776 γ-Cadinene 2.4 4.0
1810 3,7-Guaiadiene 0.5 0.7
1941 α-Calacorene 0.7 0.5
2008
Caryophyllene oxide 0.5 0.7
2071 Humulene epoxide-II 0.5 0.6
2080 Cubenol 2.7 0.6
2088 1-epi-Cubenol 5.0 1.4
2109 Furopelargone B 0.9 1.4
2187 T-Cadinol 1.5 3.4
2209 T-Muurolol 0.9 1.7
2219 δ-Cadinol 0.4 0.7
2255 α-Cadinol 2.8 5.8
2300 Tricosane 0.5 0.3
2369 Eudesma-4(15),7-dien-1β-ol 0.1 0.7
2500 Pentacosane 1.6 2.8
RRI: Relative retention indices calculated against n-alkanes
%: calculated from FID data
tr: Trace (< 0.1 %)
The plant material was hydrodistilled for 3 h using a Clevenger type apparatus. The essential oil
yield was calculated on dry weight basis corresponding to 0.5%.
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Table 4. Information on the Betula species growing in Turkey and essential oils
Betula
species
Collection Site Altitude
(m)
Collection
Period
Parts Oil Yield*
(%)
ESSE
Rize - Çamlıhemşin 1765 07.1996 Branch 0.15 12239
Rize - Çamlıhemşin 1765 07.1996 Leaf 0.11 12239
browicziana
Rize - Çamlıhemşin 1765 05.1998 Bud # 12760
Artvin - Hatila valley 2050 07.1998 Branch 0.01 12755
Artvin - Hatila valley 2050 07.1998 Leaf 0.17 12755
litwinowii
Artvin - Hatila valley 2050 05.1998 Bud 6.34 12757
Rize - Çamlıhemşin 1700 05.1998 Branch 0.1 12759
Rize - Çamlıhemşin 1700 06.1998 Leaf 0.13 12563
medwediewii
Rize - Çamlıhemşin 1700 05.1998 Bud 1.25 12759
Erzurum 1800 05.1998 Branch 0.1 12527
Erzurum 1800 05.1998 Leaf 0.63 12527
pendula
Erzurum 1800 05.1998 Bud 3.82 12527
Rize - Çamlıhemşin 1700-1800 06.1998 Branch ** 12534
Rize - Çamlıhemşin 1700-1800 06.1998 Leaf 0.56 12534
recurvata
Rize - Çamlıhemşin 1700 09.1998 Bud # 12758
*Yields are given on moisture free basis
** Due to the poor yield of oil, it was dissolved in n-hexane.
# Likens-Nickerson SDE
Analysis of the essential oils
Gas chromatography (GC). Betula essential oils were analyzed by GC using a Hewlett Packard
6890 system and an HP Innowax FSC column (60 m x 0.25 mm , with 0.25 µm film thickness)
was used with nitrogen at 1 mL/min. Initial oven temperature was 60°C for 10 min, and
increased at 4°C/min to 220°C, then constant at 220°C for 10 min and increased at 1°C/min to
240°C. Injector temperature was set at 250°C. Percentage composition of the individual
components were obtained from electronic integration using flame ionization detection (FID) at
250°C. n-Alkanes were used as reference points in the calculation of relative retention indices
(RRI). Relative percentages of the characterized components were as cited in Table 1-3.
Gas chromatography-mass spectrometry (GC-MS). GC-MS analysis was performed with a
Hewlett-Packard GCD, system and Innowax FSC column (60 m x 0.25 mm , 0.25 µm film
thickness) was used with Helium. GC oven temperature conditions were as described above, split
flow was adjusted at 50 mL/min, the injector temperature was at 250°C. Mass spectra were
recorded at 70 eV. Mass range was from m/z 35 to 425.
Identification of components. Identification of the essential oil components were carried out by
comparison of individual relative retention times with those of authentic samples or by
comparison of their relative retention index (RRI) to series of n-alkanes. Computer matching
against commercial (Wiley and MassFinder 2.1) and in-house “Baser Library of Essential Oil
Constituents” libraries made up by genuine compounds and components of known oils, as well
as MS literature data was also used for the identification.
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... The essential oils of leaves from birch species are commonly dominated by sesquiterpenoids of the caryophyllene type like αbetulenol, 14-hydroxy-4,5-dihydro-β-caryophyllene, and α-betulenol acetate. [20,21] Other sesquiterpenoids have been identified as the main compounds in some extracts. [20][21][22][23][24] Some birch species have been found to yield essential oils containing other types of secondary metabolites as their main components. ...
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Green chemistry was called to protect the environment and human beings from the used or wasted chemicals and solvents that represent hazards in the research laboratories. This chapter summarizes the fundamentals and applications of supercritical fluid extraction (SFE) as an alternate green and safe approach for the extraction of essential oils from different plants. At first, we explained essential oils and enumerated their sources and medicinal uses. Then, we discussed old technology for their extraction then presented the SFE approach as a green environmentally benign approach for essential oils extraction. The advantages of using SFE for essential oil extraction over traditional classical techniques were emphasized. SFE could reduce the use of petroleum solvents as well as decrease the extraction time compared to traditional extraction methods. The supercritical fluids (SFs) were characterized with a solubility like liquid and diffusivity like gas, which could dissolve different types of essential oils. Next, the effect of extraction parameter optimization on the SFE of essential oil was discussed. Finally, the taxonomy of different plant sources for essential oils and their SFE method of extraction were summarized and emphasized with many examples from the literature.KeywordsEssential oilsTaxonomyExtractionGreen solventsSupercritical fluid extractionMedicinal uses
Chapter
The potential applications of biotechnology for the utilization of the essential oils extracted from 56 trees, shrubs, and vines were examined. Monoterpenoids are the most common components of essential oils, followed by sesquiterpenoids, whereas, in some cases, phenylpropanoids and fatty acids can be components. Terpenoid yields from in vitro cultured calli or cell suspensions are much lower, compared to the yields from intact plant tissues. However, alkaloid caffeine can be synthesized at amounts of an order of magnitude higher than cultured calli, compared to intact plant tissues, whereas alkaloid trigonelline yields are comparable to those from plant tissues. Cineole and pinene essential oils can also be extracted from transgenic plants, such as coffee plants with less caffeine, rose geranium with more geraniol, black pepper with altered terpenoid constituency, and eucalyptus with more limonene. Biotransformations of isolated essential oil compounds produce mainly hydroxylated, epoxidated, and other catabolic products, some of them, like decalactone, lilac aldehyde, lilac alcohol, phenylethanol, and caryophyllene oxide, being perfume compounds, while others, such as anisic acid, benzyl alcohol, verbenone, and carveol, are also of medicinal value.
Chapter
Generally, according to biosynthetic origin, the components of essential oils are divided in two groups, including terpene origin compounds and aromatic constitutes. Essential oils have antimicrobial activity against a broad spectrum of gram-positive and gram-negative bacteria. The antimicrobial activity of essential oils are often related to their major components, even though the presence of minor compounds and the ratio between active constituents also play crucial role due to synergistic effect. Other antimicrobials than essential oils have been reported to have interaction with essential oils to outcome synergistic, additive or antagonistic effects. Inhibitory action of essential oils against food microorganisms, turn them as promising antimicrobial agents for food application. Effectiveness of antimicrobial activity of essential oils in gaseous phase without requiring straight contact with microorganisms can be considered as a promising way to develop antimicrobial packaging. Antimicrobial activity of essential oils could be retained or improved by encapsulation.
Article
A new caryophyllene, 4,5-epoxy-13-hydroxy-β-caryophyllene, has been isolated from Pterocaulon serrulatum using a bioassay-guided fractionation procedure. Several known compounds were also identified in the extracts, including 14-hydroxy-β-caryophyllene, three simple coumarins and a flavanone.
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A review is given of the literature over the period from the middle of the 1950s to the beginning of the 1980s on the distribution in nature, the biological activity, the conformation, and the chemical transformations of sesquiterpenes of the caryophyllene type.
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The quantitative amounts of the essential oil of the European white birch of the Yakut population in the annual cycle and its component composition have been investigated.
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The occurrence of a series of new constituents which can be considered as Diels-Alder adducts of methyl vinyl ketone and ocimene (→1–4), myrcene (→9, 10) or β-far-nesene ( →11, 12), respectively, was reported. Furthermore, the structures of four isomeric cyclohexene derivatives could be established as adducts 21–24 of (E, Z)- and (E, E)-1,3,5-undecatrience and methyl vinyl ketone. Another series of constituents having the norbornane skeleton represents adducts 25–32, and 33–40 of methyl cyclopentadiene and 1-octen-3-one or methyl vinyl ketone, respectively. In accordance with Alder's endo-rule the endo-isomers are preponderant in the natural as well as in the synthetic mixtures. Most of these constituents could also be identified in a lavender absolute as well as in a freshly prepared hexane extract of lavender flowers (Lavandula officinalis CHAIX).
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The absolute configuration of the nor-sesquiterpene aldehyde birkenal isolated from essential oil of Betula pubescens (Betulaceae) buds was proved by chemical correlation with caryophyllene.
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The isomerization of β-caryophyllene (3), under treatment with SeO2, is described. Chemical correlations, between 3 14--hydroxy-β-caryophylllene (6z) from Juniperus oxycedrus, are establised. High resolution 1H NMR spectra and analysis by molecular mechanics of 3, 6 and 14-acetoxy-β-caryophyllene (7) indicate the existence of two conformational isomers, βα and ββ, in each compound. At 35°C, the βα conformer predominates in 3 and 7 but the ββ conformer predominates in 6. The higher precentage of 6ββ possibly derives from an intramolecullar hydrogen bond. The treatment of 3, 6 and 7 with m-CPBA generates, in each case, two diasteromeric 4,5-epoxi-derivatives. The epoxides obtained from 6 have been isolated and analysed separately.
Article
The sesquiterpene from Juniperus oxycedrus L. (Cupressaceae), previously assigned as 15-hydroxy-9-epi-β-caryophyllene with the unusual cis-ring junction, has been shown to be the trans-fused isomer, 15-hydroxy-β-caryophyllene. The absolute stereochemistry for this compound has been determined by synthesis from (−)-β-caryophyllene.