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BIOCHEMISTRY RESEARCH TRENDS
ESSENTIAL OILS PRODUCTION,
APPLICATIONS AND HEALTH BENEFITS
ANABERTA CARDADOR MARTÍNEZ
AND
VÍCTOR M. RODRÍGUEZ GARCÍA
EDITORS
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Published by Nova Science Publishers, Inc. † New York
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In: Essential Oils Production … ISBN: 978-1-53614-369-0
Editors: Anaberta Cardador Martínez et al. © 2018 Nova Science Publishers, Inc.
Chapter 13
CINNAMON ESSENTIAL OIL: CHEMICAL
COMPOSITION AND BIOLOGICAL ACTIVITIES
Peter Knauth, Zaira López López,
Gustavo Javier Acevedo Hernández
and María Teresa Espino Sevilla
Universidad de Guadalajara, Centro Universitario de la Ciénega,
Ocotlán, Jalisco, Mexico
ABSTRACT
The botanical name “Cinnamomum” is derived from the Hebraic and Arabic term
amomon, meaning fragrant spice plant. The common name Cinnamon is derived from the
Greek word kinamon that loosely means “Arabian spice”. The aroma of Ceylon
cinnamon has a very characteristic sweet, warm, spicy, and woody aroma, the flavor is
warm, spicy and aromatic, the essential oil also has a sweet, spicy, slightly woody, and
clove-like aroma. The major chemical constituents of cinnamon bark oil are
cinnamaldehyde (65-80%) and eugenol (5-10%). Other abundant constituents are the
cinnamyl group such as cinnamic acid and cinnamyl acetate, compounds containing
endocyclic double bond as α-thujene, α-terpineol, α-cubebene, unconjugated exocyclic
double bond eugenol, β-caryophyllene, terpinolene and hydroxyl-substituted aliphatic
compounds. Cinnamon essential oil has biological activities, for instance, antioxidant,
antimicrobial, antifungal, antidiabetic among others. This work describes the botanical
origin of cinnamon, production of its essential oil and come of the biological activities
attributed not only to essential oil but also to individual components.
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216
Keywords: cinnamon, cinnamaldehyde, hydro-distillation, antioxidant, antibacterial,
antifungal, cytotoxicity
INTRODUCTION
The botanical name “Cinnamomum” is derived from the Hebraic and Arabic term
amomon, meaning fragrant spice plant. The common name Cinnamon is derived from the
Greek word kinamon that loosely means “Arabian spice” [1]. There are about 250 species
of the genus Cinnamomum but only two species are industrially widespread; these are,
Cinnamomum verum (previously known as Cinnamomum zeylanicum) and Cinnamomum
cassia. They are mainly located in Asia and Australia. Cinnamomum verum receives the
common names true cinnamon or Ceylon cinnamon because it is native to Sri Lanka
which is also named Ceylon. In the case of C. cassia, a native of southern China, the
common names are cassia, Chinese cinnamon, false cinnamon, cassia lignea, bastard
cinnamon, cassia-bark tree, Chinese cassia or Saigon cinnamon. Cinnamon is considered
one of the oldest herbal medicines, the Chinese were already using it in the traditional
medicine before 2500 BC, it is mentioned in the Bible and it was used by ancient
Egyptians as embalming fluid [1]. The Portuguese invaded Sri Lanka immediately after
reaching India in 1536 because they found cinnamon trees growing there and exported
this spice to Europe during the early 16th and 17th centuries [1]. Nowadays, the most
important commercial cultivations outside of Sri Lanka are India, Africa, South America,
the West Indies, Indonesia and Seychelles [1]. The food industry prefers the bark and leaf
oil of C. verum. The food and pharmaceutical industry use the oil from both C. verum and
C. cassia [2]. Cinnamon is commonly used as bark sticks, bark powder, bark essential oil,
leaf essential oil or oleoresin. The aroma of Ceylon cinnamon has a very characteristic
sweet, warm, spicy, and woody aroma, the flavor is warm, spicy and aromatic, the
essential oil also has a sweet, spicy, slightly woody and clove-like aroma. Cinnamon is
used as a flavor ingredient in the confection industry around the world, as a condiment in
several dishes or in several alcoholic and non-alcoholic beverages [3]; on the other hand,
due to its fragrance, it can be incorporated into different varieties of perfumes and
medicinal products. This spicy taste and fragrance are due to the presence of
cinnamaldehyde [4]. Thus, the major chemical constituents of cinnamon bark oil are
cinnamaldehyde (65-80%) and eugenol (5-10%). Other abundant constituents are the
cinnamyl group such as cinnamic acid and cinnamyl acetate, compounds containing
endocyclic double bond as α-thujene, α-terpineol, α-cubebene, unconjugated exocyclic
double bond eugenol, β-caryophyllene, terpinolene and hydroxyl-substituted aliphatic
compounds as E-nerolidol, L-borneol, and borneol [5]. There are more species of the
genus Cinnamomum, such as C. burmannii Blume or Indonesian cassia, C. loureirii Nees
known as Vietnamese cassia, C. tamala (Buch.-Ham.) Nees and Eberm known as Indian
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cassia and C. cordatum (Kosterm) are found in the Malaysian peninsula; however, they
are not as industrially widespread as C. verum and C. cassia, because the content of
cinnamaldehyde and eugenol are consistently more abundant in the last two species. It is
well known that these compounds are responsible for the fragrance and most of the
biological activities of cinnamon. In this chapter, the characteristics and properties of C.
verum are described.
CINNAMON IN THE WORLD
Up to 2016, Sri Lanka has been the main supplier of true cinnamon in the world,
supplying more than 85% of the world's demand. The special spicy-sweet flavor and
aroma of cinnamon are very appreciated in Mexican and Latin American cuisines,
consumption in this region is, therefore, higher than in other markets such as the
European Union and the United States. Besides foods and beverages, cinnamon is also
used in pharmaceutical and perfumery industries (EDB, 2016). Each part of the cinnamon
tree such as bark, leaves, roots, fruits, flowers and stem vary strongly in the nature and
concentration of their biologically active compounds. The bark and leaves are the most
commercialized parts; for instance, cinnamon bark products are processed as quills.
There are three major commercial categories: quillings, featherings, and chips; quillings
are broken pieces and splits of medium quality. The main importers of cinnamon
quillings in 2004 were Mexico (59%) and the USA (9%) (Table 1). Featherings are
feather-like pieces of inner bark consisting of shavings and small pieces of bark that
remain from the quillings after processing, this product is considered of medium quality.
Chips are not peeled out from the stem, instead, they are scraped off the greenish-brown,
mature, thick, handpicked pieces of bark and are of inferior quality. Oil is extracted from
the leaves by distillation; the major importers of cinnamon leaf oil are in decreasing order
the USA, the UK, Germany, France, Spain, Italy and India (EDB statistics, 2010).
Table 1. The major importing countries of cinnamon quills from Ceylon
Country
Total import (Tons)
Percentage of total import (%)
Mexico
4,773
59
USA
752
9.4
Colombia
648
8
Ecuador
533
6.5
Peru
463
5.7
Other
459
5.7
Guatemala
204
2.5
EU
150
1.8
El Salvador
108
1.4
Total
8,090
100%
Source: SL Customs report, 2005.
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Figure 1. Illustration of the branch of a C. verum tree depicting the leaves and inflorescence. The flower
and fruits are also represented.
Cinnamon has a broad use in the food industry, but currently, the biological activities
such as antimicrobial, antioxidant, anti-inflammatory or antidiabetic properties have
become very important for the pharmaceutical industry. In this chapter, these properties
will be explained in more detail.
BOTANICAL DESCRIPTION AND DISTRIBUTION
The genus Cinnamomum encompass as many as 250 aromatic evergreen trees and
shrubs primarily located in Asia and Australia. Cinnamomum verum J. Presl, formerly
known as Cinnamomum zeylanicum Blume, and originally named by Carolus Linnaeus as
Laurus cinnamomum L., is an indigenous tree of Sri Lanka and southwestern India
commonly known as true cinnamon, Sri Lanka or Ceylon cinnamon. Although different
species of the genus are often marketed as “cinnamon”, C. verum is generally considered
to have a more delicate flavor and is preferred in the food industry. It is a moderately
sized tree that grows to around 10 to 15 m with young branches that are smooth and
brown. The bark is smooth, light pinkish brown, up to 10 mm thick with a strong pleasant
cinnamon smell and a spicy, burning taste. Bark tissues display islands of sclerenchyma
in the pericyclic region, which are connected by a continuous band of stone cells, and are
characterized by the presence of secretion cells, containing mucilage or essential oil
droplets. The tree has leathery leaves, usually opposite, glabrous, lanceolate to ovate, 7 to
18 cm long, with pointed tips. The upper surface of the leaf is dark green, shining and
smooth, while the lower surface is paler and dull. Leaves are trivenate, exhibiting the
three main nerves prominently on both surfaces (Figure 1). The inconspicuous flowers,
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which are pale yellow, are tubular with 6 lobes and grow in axillary or terminal panicles
(clusters) that are up to 20 cm long. The fruit is a small (1 to 1.5 cm long), fleshy ovoid
purple drupe that ripens to black, partly surrounded by an enlarged cup-like perianth,
which contains a single seed. The flowering time fluctuates from October to February,
and the fruit ripens in May to June. C. verum is a cross-pollinated species and flowers
display protogynous dichogamy (sequential hermaphroditism), that is to say, the male
and female phases are separated by almost a day thereby ensuring outcrossing [6-8].
Besides Sri Lanka, C. verum is also grown in Indonesia, China, and Vietnam, together
making up nearly 99% of the world’s cinnamon production [9].
EXTRACTION METHODS
Essential oils (EOs, also known as volatile oils) are complex mixtures of hundred or
more compounds, synthesized by plants in order to protect them from predators. Volatile
compounds, produced by living organisms or from plant materials like flowers, buds,
seeds, leaves, wood, fruits, roots, branches, and barks are mainly isolated by physical
means (mainly by pressing and distillation) [10, 11].
The quality of EOs depends on a) the genetic variety, b) the developmental state of
the plant, c) geographical and environmental factors such as temperature, luminosity,
relative humidity, soil composition and d) cutting, post-harvest operations and the
extraction method, being the latter the most important of all the points [12].
Essential oils can be divided into two broad categories:
Large volume oils which are usually distilled from a leafy material such as
lemongrass, citronella, cinnamon, lemon, lime and orange oils are also produced
in very large amounts.
Small volume oils which are usually distilled from fruits, seeds, buds and, to a
lesser extent, of flowers, e.g., cloves, nutmeg, coriander, vetiver and flower oils
[13].
The isolation, concentration, and purification of EOs are important processes that
have been used for years, as a consequence of the widespread use of these compounds;
the industry has largely used the hydro and steam distillation as essential oil extraction
methods.
During hydro-distillation, EOs components form an azeotropic mixture with water.
Most EOs do not mix well with water, so after condensation, they are separated by
decantation. The process can take between 1 and 10 h, but in most cases, the distillation
lasts between 3 and 4 h [14]. The extraction period influences not only the yield but also
the composition of the extract. This method can be achieved by one of two alternatives:
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Clevenger apparatus: the plant material can be extracted by immersing it in
water, which is then boiled at about 100°C. About 50% of the reported
investigations use this type of apparatus in their distillation method [14].
Steam distillation: the plant material is placed into a steam distillation chamber
and afterward steam is forced into the chamber. After the EOs has interacted with
the steam, the steam flows into a chilled chamber and condenses, providing the
EOs.
In both methods, the volatile components are transported by the vapor to a condenser.
During the condensation, layers rich in oil and rich in water are formed, which are
separated by decantation [14].
During both forms of hydro-distillation, the sample is exposed to temperatures close
to 100°C, which can induce changes in the "heat-labile" components. Prolonged heating
in contact with water can lead to the hydrolysis of esters, the polymerization of aldehydes
or the decomposition of other components, and are the principal disadvantages of these
extraction methods.
However, other extraction techniques have been developed according to the type of
plant and oil desired, for instance:
Enfleurage: is a method used for samples with small amounts of EOs, in fresh plants
(flower petals), where the use of distillation is not feasible and consists of making a
maceration by mixing a light oil with the flower petals, let it rest 1 h, afterwards the oil
has absorbed the fragrance, the oil is extracted with alcohol (ethanol) and the essence is
recovered.
Extraction by supercritical fluid: is another method to isolate the volatile compounds
of the plants, using extraction by means of supercritical carbon dioxide. Maybe superior
to the methods discussed above for its extraction speed, its selectivity and its suitability,
especially for the extraction of essential oils with thermally labile compounds. In
addition, it can be applied to a wide range of pressure and temperature conditions, which
allows the conservation of essential oils.
However, its disadvantage is that the equipment and reagents used in the process are
very expensive [14].
Solvent extraction (Soxhlet method): this method, especially for oleoresins involves a
solvent, high temperatures and therefore volatile compounds can be lost.
The pressing and microwave-assisted hydro-distillation are little used nowadays [15,
16].
The hydro-distillation method is the most commonly used one due to the low energy
consumption and low costs (for reagents and equipment) [17, 18]. According to
Anderson et al. [19], the used extraction method depends on the part of the plant: from
whole plants are made aqueous extracts; from bark can be obtained alcoholic extracts or
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EOs and from leaves EOs. Table 2 shows the composition of some samples of C. verum
and C. cassia obtained by hydro-distillation or steam-distillation.
CHARACTERIZATION
The two most important varieties of cinnamon are Ceylon (C. verum) and Chinese
cinnamon (C. cassia), their wide variety of uses, especially in health benefits, make them
important throughout the world. In such a way it is important to know their composition
and analyze their activity.
Modern analysis techniques have enabled the identification and quantification of
individual components and the study of their effects. Generally, liquid chromatography
(LC) is applied for the identification of phenolic constituents, while gas chromatography
(GC) for the identification of volatile compounds [20].
Proximate composition of cinnamon (C. verum and C. cassia) is shown in Table 2.
The oil from C. verum bark contains a high ratio of saturated fat with palmitic acid
being the main fatty acid (31-33%), followed by oleic acid (29-30%), linoleic acid (15-
16%) and stearic acid (12-14%) [21].
Table 2. Proximate composition of
C. verum
and Chinese cinnamon
(
C. cassia
) barks (%)
%
Ceylon cinnamon (C. verum)
Chinese cinnamon (C.cassia)
Moisture
9.45a
7.70a
Fat
4.69a
4.65a
Ash
3.77a
2.89a
Crude fiber
21.27
a
33.41
a
Carbohydrate
55.83
a
47.25
a
Protein
4.99a 4.65b
4.10a
Phosphorus
0.05b
0.066a
Iron
0.004b
0.0027a
Sodium
0.01b
0.0187a
Potassium
0.40b
0.197a
Calcium
0.69a
1.157a
Vitamins (mg/kg)b
B1
B2
C
Niacin
A
1.4
2.1
398
19
1750
I.U.
a Reference: [21].
b Reference: [22].
Amino acids analysis: The amino acid content of C. verum from barks is rich in
glutamic acid (13.78% protein) followed by aspartic acid (10.25% protein), leucine
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(8.80% protein), lysine (8.30% protein) and serine (6.84% protein) as well as C. cassia is
rich in glutamic acid followed by aspartic acid, leucine, lysine and valine. In general, the
amino acid profile for both barks indicates a good protein nutritional quality.
Table 3. Main compounds obtained by GC-MS of essential oil from
C. verum
and
C. cassia
using hydro-distillation
Compounds
C. verum (%)
C. cassia (%)
Bark
Leaves
Bark
Leaves
trans-Cinnamaldehyde
[1-7, 10-14]
45.1 – 97.7
2.07
87-92.20
30.4-70
cis-Cinnamaldehyde[8]
tr-2.3
Benzaldehyde [1, 5]
9.94
0.24 - 0.58
(trans)-Cinnamyl acetate[5]
(trans)-Cinnamyl acetate [13]
7.44
3.13
Limonene [5, 8, 9]
2.87-4.42
Eugenol [1, 2, 4, 5, 7-10]
0.10-74.9
85.7-87.3
Coumarin[6]
0.45
trans- cinnamic acid [7]
5-10
Linalool [1, 2]
0.72-3.78
0.97
α-Pinene [2, 8]
tr-5.76
p-Cymen [8]
tr-0.7
α-Terpineol [8]
0.1
tr
Caryophyllene [1-3, 8, 9]
1.0-5.48
1.08-1.9
1,8-Cineole [8]
tr
0.7
Benzyl Benzoate [9]
2.19
Cinnamyl alcohola [9]
Cinnamyl alcoholb [10]
1.25
5.13-8.21
β-Pinene [1, 3, 8]
0.17-0.44
Methyl eugeno [10] l
5.23
Eugenyl acetate [2]
6.07
-Guaiene
[1]
1.51-7.34
Terpinen-4-ol [8]
0.1
tr
2'-Methoxy- cinnamaldehyde [8]
1.5
Copaene [1, 3]
0.68-3.86
3-Methoxy-1,2-propanediol [12]
29.30
o-Methoxy cinnamaldehyde [12, 13]
4.67
25.4
Catechin [11]
1.057
Caffeic acid [11]
0.015
a Steam distillation process
b Hydro-distillation using Clevenger type apparatus
c Water and alcohol extracts process
tr = traces
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223
trans-
Cinnamaldehyde
Eugenol
(R)-Limonene
Cinnamyl acetate
Benzaldehyde
Caryophyllene
(R)-Linalool
-Pinene
-Guaiene
Copaene
p-Cymene
Coumarin
Figure 2. Structures of the most abundant constituents of essential oils from C. verum
Anti-nutritional factors of C. verum and C. cassia are phytic acid (mg/kg sample) 835
and 1291, respectively [21].
The major compounds of C. verum obtained by hydro-distillation were trans-
cinnamaldehyde in the bark (66.3-97.7%), eugenol in the leaves (85.7-87.3%) and
cinnamyl acetate in the fruit stalks (36.6%). On the other hand, Singh et al. [4] used
Soxhlet extraction to obtain oleoresins, where they detected traces (tr < 0.01) of p-
cymene and α-terpineol and caryophyllene (1.0%) in the leaves and bark respectively
(Table 3).
Other reference shows that aromatic plants are rich in volatile oils, responsible for
pleasurable aromas. The main flavor compound in cinnamon EOs extracted from the bark
is cinnamaldehyde (56-78%), while in cinnamon EOs extracted from leaves, eugenol (60-
77%) is the main compound. Cinnamaldehyde is the responsible for the sweet taste of
cinnamon. In sweet food, there is a synergistic effect that enhances the sweet sensation of
the food when combining the sweet taste of sugar and the sweet aroma of cinnamon [22].
The variation on the composition of the same genus of cinnamon can be greatly
attributed to the differences in species, plant varieties, growth conditions, harvesting
O
H
CH2
O
H3C
HO
H3C CH3
CH3
O CH3
O
H O
H
H2C
CH3
CH3
H
CH3
CH2
H3C CH3
H3C OH
CH3
H3C
H3C
CH3
CH3
CH3
H3C
HH
H
CH3
CH3
H3C
OO
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α
Peter Knauth, Zaira López, Gustavo Acevedo & Teresa Espino
224
times, soil properties, climate, origin, environmental conditions and geographic
parameters [21, 23, 24].
Singh et al. [4] used hydro-distillation using Clevenger’s apparatus to obtain EOs
and GC and GC-MS for the characterization of the EOs, where showed the chemical
composition of volatile oil of leaves and barks of cinnamon, where 19 components were
detected by GC-MS, the main component of C. verum leaves was eugenol (87.3%)
followed by bicyclogermacrene (3.6%), α-phellanderene (1.9%), β-caryophyllene (1.9%),
aromadendrene (1.1%), p-cymene (0.7%) and 1,8-cineole (0.7%). Moreover, its oleoresin
showed the presence of 25 components accounting for 97.1% of the total amount with
eugenol (87.2%) as a major component.
Regarding cinnamon bark volatile oil showed the presence of 13 components,
accounting for 100% of the total amount. (trans)-Cinnamaldehyde was found as the major
component along with δ-cadinene (0.9%), α-copaene (0.8%) and α-amorphene (0.5%),
whereas its bark oleoresin showed the presence of 17 components accounting for 92.3%
of the total amount. The main components were (trans)-cinnamaldehyde (49.9%),
coumarin (16.6%), δ-cadinene (7.8%), α-copaene (4.6%), (cis)-cinnamaldehyde (1.5%),
ortho-methoxy cinnamaldehyde (1.5%) and β-bisabolene (1.4%) along with several other
component [4]. Some structures of cinnamon essential oil compounds are shown in
Figure 2.
The properties of cinnamon (Ceylon and cassia) come from its essential oils and
compounds, particularly cinnamaldehyde. This compound gives cinnamon its flavor and
aroma and is also responsible for many of its health benefits.
However, the most important distinction between them may be the presence of
coumarin, a natural plant secondary metabolite that acts as a blood thinner. Cassia
contains approximately 1% coumarin, while Ceylon contains only 0.004%, or 250 times
less [25]. This is so low that it is often undetectable. It is contraindicated for anyone
taking prescription blood thinners. Coumarin has also been shown to be toxic to the liver
and kidneys, and it may also be carcinogenic, which can negate any health benefits of
cinnamon.
ANTIBACTERIAL
Although many studies on the antimicrobial activity of CE are available, the number
of included publications reduced considerably after applying exclusion criteria of i) no
reported MIC, ii) strains different from the reference strains used, iii) non-bark parts, iv)
an extraction solvent other than water, alcohol or hydrodistillation, v) concentration of
commercial essential oil not indicated. Generally, the reported MICs against reference
strains was relatively high with typically 200-560 µg/ml for Gram-positive strains (with
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some exceptions having MICs up to 3,800 µg/ml) and, with higher variations, 140-1600
µg/ml (and an exception up to 5,800 µg/ml) for Gram-negative bacteria (Table 4).
Table 4. Reported Minimal Inhibitory Concentration (MIC) of extracts or essential
oils from
C. verum
against bacterial reference strains
Strain: Gram (-)
Num.
MIC µg/ml
Reference
Enterobacter aerogenes
ATCC13048
>1024
[10]
Escherichia coli
ATCC8739
>1024
[10]
ATCC10536
>1024
[10]
ATCC11105
2500
[9]
ATCC25921
625
[9]
ATCC25922
280 - 390 - 1120 - 1250
- 1600
[3] - [4] - [12] - [9] -
[8]
O157:H7
625
[9]
Klebsiella pneumoniae
ATCC11296
256
[10]
ATCC13883
140
[12]
ATCC15380
3200
[8]
ATCC700803
195
[4]
Proteus mirabilis
ATCC7002
140
[12]
Proteus vulgaris
ATCC13315
1600
[8]
Salmonella typhimurium
ATCC13311
1560
[4]
ATCC14028
140
[12]
Providencia stuartii
ATCC29916
256
[10]
Acinetobacter lwoffii
ATCC19002
35
[12]
Pseudomonas aeruginosa
ATCC27853
280 - 390 - 800
[12] - [4] - [8]
ATCC49189
5200
[5]
PA01
>1024
[10]
Haemophilus ducreyi
ATCC33940
50
[5]
Bacillus cereus
ATCC11778
560
[2]
Bacillus subtilis
ATCC6633
1600
[8]
Bacillus licheniformis
ATCC14850
3800
[7]
Listeria monocytogenes
ATCC19177
400
[2]
Staphylococcus aureus
ATCC19177
256
[6]
ATCC25923
3200
[8]
ATCC29213
370 - 390 - 560
[3] - [4] - [12]
Enterococcus faecalis
ATCC29212
97.5 - 1120
[4] - [12]
Lactobacillus casei
ATCC11578
300
[1]
Streptococcus pyogenes
ATCC19615
560
[12]
Streptococcus pneumoniae
ATCC49619
35
[12]
Streptococcus mutans
ATCC700610
195
[4]
ATCC25175
200
[1]
Streptococcus mitis
ATCC49456
350
[1]
Streptococcus bovis
ATCC9809
195
[4]
Mycobacterium tuberculosis 37Ra
MTCC300
100
[11]
Mycobacterium smegmatis
CMM2067
70
[12]
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Table 5. Reported Minimal Inhibitory Concentration (MIC) of extracts or essential
oils from
C. verum
against fungal reference strains
Strain
Num.
MIC µg/ml
Reference
Aspergillus fumigatus
AQC-A31
160
[31]
Candida albicans
ATCC2091
350
[30]
ATCC10231
70-160
[31, 32]
ATCC90028
1120 - 7500
[29, 32]
Candida parapsilosis
ATCC90018
<40
[32]
ATCC200219
80
[31]
Candida glabrata
ATCC1300
160
[31]
ATCC90030
15000
[29]
Candida tropicalis
ATCC7110
160
[31]
Candida krusei
ATCC6258
<40
[32]
Only a few studies deal with the mode of action to explain their antibacterial effects.
Within 1 h, commercial essential oils from C. cassia (C. verum was not analyzed) let the
intracellular ATP content of Escherichia coli O157:H7 or Listeria monocytogenes 2812
significantly decrease, acidified their cytosol and finally caused visible membrane
damage by a release of intracellular constituents (measured at λ 260 nm) [26]. The
principal component of cinnamon, trans-CA, acts as a competitive inhibitor of the
carboxyl-transferase subunit of the AcetylCoA-Carboxylase (EC 6.4.1.2), the key
enzyme for fatty acid synthesis, competing with the coenzyme biocytin (i.e., biotinylated
lysine) and not with the substrate AcetylCoA or product MalonylCoA [27]. Cinnamon
essential oils not only inhibit bacterial growth but also suppress quorum sensing and
biofilm formation: A commercial cinnamon bark essential oil (the concentration of its
constituents remains unclear) at 0.05% (v/v) nearly completely inhibited biofilm
formation of Pseudomonas aeruginosa with CA being the main active compound.
Additionally, at the mentioned concentration, cinnamon bark essential oil completely
inhibited the expression of the virulence factors pyocyanin and PQS, although not
pyochelin or rhamnolipids; the active compound here was especially eugenol and to a
lesser extent CA. Biofilm formation of E. coli EHEC was strongly reduced at 0.01% (v/v)
cinnamon bark essential oil and the most active compound was eugenol and to a much
lesser extent CA; the expression of the virulence factor stx2 (Shigella-like toxin) was
reduced only slightly [28].
ANTIFUNGAL
Applying the same exclusion criteria as for antibacterial activity, much less
antifungal studies are published. While a watery extract of C. verum bark was not very
effective against Candida (MIC = 7,500-15,000 µg/ml), the active compounds could be
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identified as trans-CA and O-methoxy-CA (MIC = 60-250 µg/ml) [29]. Other authors
detected much lower MICs (40-350 µg/ml) against several other fungi and yeast [30-32],
and confirmed that CA is the main active. Li et al. [33] found that cinnamon essential
oils on Rhizopus nigricans increased membrane permeability and decreased membrane
ergosterol content as well as succinate dehydrogenase and malate dehydrogenase activity,
which would explain its fungicidal effects.
ANTIOXIDANT CAPACITY (AOC)
Again, studies reporting results using plants other than C. verum or other parts than
the bark were excluded. Cinnamon bark mainly contains phenylpropanoids but also many
terpenoids, thus, it can be expected that essential oils have antioxidant properties. The
total phenolic content (TPC) from 5 different publications can be averaged (± SEM*1.96)
to 24.4 ± 13.5 µmol/g GAE (gallic acid equivalent) [34-39]. Even with the a priori
exclusions, results from different publications are very difficult to compare because i)
different (and not further characterized) raw material was used, ii) extractions were done
with different solvents and iii) different standards and concentrations were employed as
controls (ascorbate, gallate, Trolox, butylated hydroxyanisole as the most common). For
instance, for the frequently used radical scavenging test ABTS values of 1.1, 18.5, 121.6
and 1119.9 µmol/g TE (Trolox equivalent) are reported, which clearly illustrates the
problem [34, 35, 38, 39]. Therefore, it is easier to compare results quantitatively only
within the same publication and compare results among publications only qualitatively.
At least three groups found that CE has high antioxidative capacity (AOC) compared to
other spices: Shan et al. [35] found cinnamon for TPC and ABTS placed second among
26 spices and the same result, using the same tests, obtained by Przygodzka et al. [39]
who tested cinnamon against 11 different spices. In a more extensive work, Lin et al.
[40] found cinnamon having also the second highest TPC among 42 spices and the
highest DPPH radical scavenging capacity. Even more interesting is the fact that they
could attribute the antioxidant effect principally to the compound eugenol and not to the
main constituent trans-CA.
In vivo studies on antioxidative effects are less common. Dhuley et al. [41] revealed
that Wistar rats under a high-fat diet increased the activity of several antioxidant enzymes
(catalase, superoxide-dismutase, GSH-peroxidase), compared to a normal diet; and this
effect was even more pronounced for a high-fat diet supplemented with 10% cinnamon.
When diabetic rats were treated with 1.2 g/kg*d polyphenol-enriched CE, superoxide-
dismutase and GSH-peroxidase restabilized from about 70% to about 90% [42]. Much
more interesting is that in a study with 18 healthy persons the daily intake of 100 mg
cinnamon during 10 d decreased the plasma lipid peroxidation from 5.3 to 3.25 nmol/ml
[43].
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The antioxidant properties of CEs vary considerably. This is easy to understand,
because different geographic locations, the seasonal stage and age of the plant (bark) at
the moment of harvest, as well as the age of the sample and their storage conditions
(many were commercial samples), are not considered. Nevertheless, in all comparative
studies of spices, CEs were among those with the highest AOC (The same considerations
of the variability of biological material also apply to the extracts from other spices).
CYTOTOXICITY
Only studies reporting results on C. verum bark extracts or its components are
considered here. A watery extract led to cell cycle arrest in G2/M-phase of the T-
lymphocyte cell line Jurkat at 75 µg/ml and of the monocyte cell line U937 at 150 µg/ml
[44]. An acetonic extract acts on the colon cell line HT29 with a cytotoxic concentration
of CC50 = 190 µg/ml, i.e., in a similar range [37]. But most in vitro studies deal with
isolated and purified or acquired (pure) substances in order to narrow the cytotoxic
compound.
For trans-CA, the main compound of C. verum extracts, the reported cytotoxic
concentration can be averaged (± SEM*1.96) to CC50 = 38.2 ± 22.9 µM, depending on
the cell line and detection method [45-49].
Derivates from trans-CA like cinnamate and cinnamyl ester or cinnamyl alcohol are
less active than CA itself, indicating the importance of the free aldehyde group for the
biological activity (Figure 3). Moreover, the reduction of the propenal side chain to
propanal also reduced the biological activity [47]. All reports stated that CA induces
apoptosis: cell cycle arrest for A375 melanocyte in G1-phase [47] and for the colon cell
line HCT116 in G2/M-phase [48]. Moreover, it stimulates cytochrome-c release (after 2
h), activates caspase 9 (after 4 h) and caspase 3 (after 6 h) and causes DNA-laddering
(after 8 h) in HL60 [45]. One important step for apoptosis induction, caspase 3 activation,
could be confirmed by Cabello et al. [47], Chew et al. [48] and Chuang et al. [49].
Additionally, mitochondrial membrane potential decreased, ROS-formation [45] and,
thus, the expression of 18, from 84 assessed, ROS-related genes, increased [47]. Other
related effects are an inhibition of JAK2, STAT3 and STAT5 signalling [49], suppression
of NF-κB-regulated gene expression and reduction of cell invasion [47].
The derivate 2-methoxy-CA (more typical for C. cassia) is cytotoxic to the
hepatocyte cell line SK-Hep1 with CC50 = 25.7 µM and causes similar effects as CA
itself: cell cycle arrest, loss of mitochondrial membrane potential, caspase 3 and 9
activation and inhibits NF-κB-regulated gene expression [50].
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Figure 3. Derivates from Cinnamaldehyde
HYPOXIA, ANGIOGENESIS AND METASTASIS
Solid cancers are characterized by suffering hypoxia and nutrient deprivation, which
triggers angiogenesis, the basis for spreading metastasis. In the renal cell line RCC4
trans-CA inhibits Hif-1α-expression (Hypoxia-inducible factor) in a dose-dependent
manner, a protein which triggers hypoxia angiogenesis via VEGF (Vascular Endothelial
Growth Factor). As far as the mode of action, it is assumed that CA does not inhibit the
proteasomal degradation of Hif-1α, but it inhibits the phosphorylation of mTOR and thus
the transcription of Hif-1α [51]. Moreover, 100 µM CA revert the stimulatory adhesion
effect of the Tumor Necrosis Factor-alpha (TNFα) for the monocyte cell line THP1 at the
endothelial cell line EA.hy926. This effect is caused by strongly inhibiting the expression
of ICAM-1 (Intercellular Adhesion Molecule) and, to a lesser extent, of VCAM-1
(Vascular Cell Adhesion Molecule). Additionally, the TNFα-induced activation of NFκB-
regulated gene expression was inhibited while the expression of Nrf2-controlled genes
like thioredoxine reductase, a γ-glutamylcystein synthetase and, in consequence,
glutathione itself was increased [52]. The effect of CA on Nrf2-dependent gene
expression could be confirmed by Chew et al. [48].
Apart from in vitro studies, some of those effects could be demonstrated in animal
models: 5*106 tumor cells (Renca) were injected into mice after one week and were then
treated with 76 µmol/kg*d (i.p.) CA for one week: While the body weight did not
change, the tumor size decreased by 80% and reached its original size; although, when
the treatment was prolonged to 3 weeks, the tumor size did not decrease further. On the
other hand, angiogenesis was reduced within a tumor: the hemoglobin content reduced by
75% and PECAM-1 expression (Platelet Endothelial Cell Adhesion Molecule) reduced
by 50% [51].
ANTI-INFLAMMATION
As described above, trans-CA reduces TNFα-induced NFκB-regulated gene
expression; and those genes are, among others, involved in proinflammatory processes
Cinnamyl alcohol Cinnamate Cinnamyl acetate 2-Methoxy
cinnamaldehyde
Figure 3. Derivates from Cinnamaldehyde
OH
O
OH
O CH3
O
O
H
OCH3
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(e.g., iNOS and COX-2): Indeed, when mouse J774A.1 macrophages were pre-incubated
24 h with CE, followed by a stimulation with 25 µg/ml LPS (LipoPolySaccharid) during
4 h, a reduction of gene expression by 50% could be achieved for COX-2 with 50 µg/ml
extract and for IL-1β or IL-6 with 10 µg/ml extract [37]. This anti-inflammatory effect
could be narrowed to CA being the active compound to strongly reduce the liberation of
NO, TNFα, IL-1β and IL-6 in mouse BV6 microglial cells after their stimulation with
LPS; eugenol exhibited only a weak and cinnamyl acetate nearly no effect on these
markers [53]. Additionally, rat enterocytes decreased proinflammatory cytokines like
TNFα, IL-1β, IL-6 by half upon a treatment with 100 µg/ml CE, and at the same time
stimulated the JNK, p38, and ERK-pathways [54].
The anti-allergenic potential was studied by Hagenlocher et al. [55], who found that
human intestinal mast cells (hiMC), treated with 18 µg/ml ethanolic C. verum extract,
reduced IgE-induced FcεRI-mediated degranulation by 60%, and the release of cysteinyl
leukotrienes (cysLT) by 75%. Moreover, the expression of several other proinflammatory
chemokines (IL-8, MCP-1, MIP-1α, RANTES) and cytokines (TNFα) was nearly
abolished. This could likely be achieved by inhibiting the IgE-signalling cascade: JNK,
p38 and AKT were inhibited while ERK stayed unchanged; this culminates in an
inhibition of NFκB-induced gene expression and mTOR-induced protein biosynthesis.
Independently, 10 µM CA inhibits JNK, p38 and ERK-signalling in renal fibroblasts
NRK-49F with high glucose medium [56]. In a second study, Hagenlocher et al. [57]
could demonstrate that CA is the active compound, inhibiting degranulation with IC50
60 µM, release of cysLT with IC50 35 µM and the expression of the mentioned
cytokines abolished at 50 µM. This effect could even be demonstrated in animal models:
When IL-10-/--mice, a model for human inflammatory bowel disease, were fed with 800
mg/kg*d cinnamon bark, then the bowl wall thickness decreased (although not achieving
normal values) and the chemokines MCP1, MIP1α, MIP2 and the cytokine TNFα
decreased by 3 times while TGFβ increased by approximately 3 times. Moreover, no
impact on the tight junctions, measured as the expression of claudin, occludin, and ZO-1
could be observed while phosphorylated IκB decreased, indicating an inhibition of
NFκB-signalling [58]. Besides reducing effects of nutritional allergic reactions, CA can
reduce sneezing and nose rubbing by 35% in rats with allergic rhinitis, when each nostril
was treated with 400 µg twice per day [59].
As CA reduces the liberation of proinflammatory factors in mouse BV6 microglial
cells, anti-neuroinflammatory effects are postulated [53]. Indeed, 110 µg/ml of watery
CE inhibited tau-aggregation, a hallmark of Alzheimer disease (AD), in vitro by 75%. At
220 µg/ml, even a disassembly of pre-formed recombinant tau-fibers could be achieved.
The active compound for this action was identified as proanthocyanidin trimer, which
acts at 75 µM similar to 110 µg/ml extract. CA exhibited only a slight inhibition of tau-
aggregation [60]. Besides tau-aggregation, Aβ-amyloid fibrils are also probably
neurotoxic and contribute to neurodegeneration and dementia in the AD. Watery CE
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inhibits Aβ40-fibrillization with an IC50 = 0.7 µg/ml, while it is not cytotoxic to rat
neuronal PC12 cells up to 1 mg/ml; the active principle is also assumed to be polyphenols
[61].
Finally, the above mentioned anti-inflammatory effect of CE could also be
demonstrated in diabetic rats, an important mechanism to reduce insulin resistance:
NFκB-signalling as well as iNOS-activation was reduced from about 565-590% in
diabetic rats to nearly normal 125% after diabetic rats were treated with 1.2 g/kg*d
polyphenol-enriched CE [42].
Cinnamtannin A1 Cinnamtannin B1
Figure 4. Polyphenols from proanthocyanidins from C. verum
ANTI-DIABETES
Many effects of cinnamon on Diabetes are reported, but frequently the different
species of cinnamon are not considered and again, studies considering plants or parts
other than C. verum bark are not considered. First, CE can reduce the intestinal
absorption of carbohydrates by inhibiting the pancreatic α-amylase (in vitro, IC50 = 1.23
mg/ml), which reduces starch degradation, and by inhibiting the α-glucosidase maltase
(in vitro, IC50 = 0.77 mg/ml), that in turn reduces the degradation of limit dextrins, and
the sucrose α-glucosidase (in vitro, IC50 = 0.42 mg/ml), which inhibits the degradation of
fructose [62]. Similar results are also reported by Ranilla et al. [63]. Shihabudeen et al.
[64] revealed that maltase is reversibly inhibited by competition. Diabetic rats liberate
only 40% of the insulin compared to healthy rats, but when those rats are fed with 4
g/kg*d cinnamon, insulin liberation was restored to 97% [65]. Babu et al. [66] and later
Anand et al. [67] narrowed this effect to CA, which restores insulin liberation to normal
values when diabetic rats were fed with 150 µmol/kg*d CA. The next effect is that 110
µM cinnamtannin B1, a proanthocyanidin, stimulate insulin receptor phosphorylation,
O
HO
OH
OH
OH O
O
OH
OH
HO
OH
OH
O
HO
OH
OH
OH O
OO
OH
OH
OH
OH
OH
OH
OH
HO
HO
HO
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thus activation, by three times compared to unstimulated cells [68]. This action could be
confirmed by Qin et al. [69], who measured an increase of mRNA for the insulin
receptor from 40% to 80%, for IRS-1 (Insulin Receptor Substrate 1) from 45% to 95%
and for AKT from 55% to 110% in enterocytes from diabetic hamsters when treated with
50 µg/ml CE and compared to healthy controls. Upon insulin receptor activation,
especially in myocytes and adipocytes, GLUT4 is transported to the cell membrane to
increase glucose uptake as could be demonstrated by several groups: In vitro, 200-400
µg/ml CE simulated glucose uptake by adipocytes slightly, similar to 0.5 nM insulin [70].
Shen et al. [71] found that already 10 µg/ml CE increased glucose uptake in adipocytes
by 50%, similar to 100 nM insulin; moreover, this could be verified by determining the
translocation of GLUT4 into the cell membrane in adipocytes. Skeletal muscle cells in
diabetic rats reduced GLUT4 in the cell membrane to 40%, which can be recovered to
75% by a treatment with 150 µmol/kg*d CA [67]. Nikzamir et al. [72] showed that 50
µM CA additionally increased GLUT4 gene expression by three times. Contrary to
Taher et al. [68] and Qin et al. [69], Shen et al. [73] revealed that CE does not act on
the insulin receptor directly but stimulates the phosphorylation and hence activation of
the AMPK (AMP-sensitive Kinase), which caused the translocation of GLUT4.
However, upon activation, and especially in gluconeogenetic tissues (i.e., liver and
kidney), enzymatic activities are restored to normal values in diabetic rats:
gluconeogenesis is inhibited, i.e., PEPCK, fructose-1,6-bisphosphatase and glucose-6-
phosphatase activities decreased from 150-300% to 100-120%, and glycolysis is
stimulated, i.e., phosphofructokinase-1 and pyruvate kinase activities increased from 40-
50% to 85-95% in diabetic rats treated with 4 g/kg*d cinnamon, 100 mg/kg*d CE or 150
mmol/kg*d CA [65, 67, 74]. This causes a restoration of glycogen synthesis, which is
necessary to lower blood glucose; liver glycogen content increased again from 40-50% to
85-95% in diabetic rats treated as mentioned above [66, 67, 74]. The final effect on blood
glucose values depends considerably on the design of the study (i.e., insulin resistance
induced by streptozotocin or by fructose feeding): Treated diabetic rats decreased blood
glucose from 150% to 105% when treated with 100 mg/kg*d CE [74], from 345% to
115% when treated with 5% essential oils [75] or from 460% to 190% when fed with 5
g/kg*d cinnamon [65]. Probably CA caused this effect as rats fed with 150 mmol/kg*d
CA decreased blood glucose from about 520% to 150-200% [66, 67]. Others reported
weaker effects, e.g., a decrease from 415-550% to 320-355% was found after a treatment
with 100-600 mg/kg*d CE by Shen et al. [71] or Ranasinghe et al. [76]. In any case, all
studies agreed with a beneficial, i.e., blood glucose lowering effect. In consequence,
glycosylated hemoglobin (HbA1c) was also reduced: from 300% to nearly normal values
(120%) by a treatment with 100 mg/kg*d CE [74]. CA could be identified as the principal
component responsible for this effect [66, 67].
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Figure 5. Proved action of CA Cinnamaldehyde, CE Cinnamon Extract or CT Cinnamtannins:
Blue: proteins (enzymes, transcription factors). Green arrow: activation; Red line with a square: inhibition; dashed arrow: reduced action; Bold arrow: activated
action; Dotted arrow: activated action (described elsewhere). FFA free fatty acid; Fru fructose; Glc glucose; Hb hemoglobin; HDL high-density lipoprotein; IDL
intermediate density lipoprotein; LDL low-density lipoprotein; LPS Lipopolysaccharide; TAG triacylglyceride; TNFα tumor necrosis factor alpha; VLDL very
low-density lipoprotein. AMPK AMP-sensitive Kinase; AS160 Akt substrate of 160 kDa; ChREBP carbohydrate responsive element binding protein; FBPase
fructose-1,6-bisphosphatase; G6Pase glucose-6-phosphatase; GLUT glucose transporter; HSL hormone-sensitive lipase; IR insulin receptor; IRS insulin
receptor substrate; MTP microsomal TAG-transfer protein; NFκB nuclear factor kappa B; PEPCK phosphoenolpyruvate carboxykinase; PFK
phosphofructokinase; PK pyruvate kinase; PKA protein kinase dependent on cAMP; PLIN perilipin; SREBP sterol responsive element binding protein; TLR
Toll-like receptor; UCP uncoupling protein
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As a side effect, and a frequent problem in diabetic patients, blood lipid values
improved: in diabetic rats blood TAG reduced from 230-275% to 95-140% when diabetic
rats were fed with 4 g/kg*d cinnamon, 100 mg/kg*d CE or 5% essential oil [65, 74, 75];
this effect could be reproduced by feeding 150 mmol/kg*d [66]. At the same time, blood
LDL-cholesterol decreased from 170% to 105% in diabetic rats treated with 5% essential
oil [75] and blood HDL-cholesterol increased to nearly normal values: from 50-75% to
90-93% in diabetic rats treated with 100 mg/kg*d CE or 5% essential oil [71, 75]. The
latter effect could be attributed to a treatment with 150 mmol/kg*d CA [66]. This positive
effect on lipoprotein may be explained when diabetic hamster enterocytes were treated
with 50 µg/ml CE: expression of MTP (Microsomal TAG-transfer Protein; required to
form lipoproteins in Golgi-apparatus) decreased from 190% to 150% and SREBP1c
(Sterol Responsive Element Binding Protein; regulates genes for de novo lipogenesis)
decreased from 275% to 150% [69]. Indeed, enterocytes from diabetic rats exposed to
100 µg/ml CE reduce ApoB48 liberation into medium to 60% compared to heathy rat
cells. Recently, it could be shown that 100 µM CA activate PKA and the subsequent p38
pathway, which in hASC (Human Adipose-derived Stem Cells) stimulate thermogenesis
by activating HSL (Hormone Sensitive Lipase) and PLIN1 (Perilipin-1) and induces the
expression of UCP-1 (UnCoupling Protein-1). CA activates also FGF21 (Fibroblast
Growth Factor 21), which is required for a long-term reprogramming of adipocytes [77].
Astonishingly, although many beneficial studies on anti-diabetic effects in vitro and
in vivo are published and even several molecular mechanisms are revealed, CE from C.
verum have not been studied much in clinical trials; most studies on human beings were
done with extracts from C. cassia. We found only one clinical trial where persons
ingested 3 g/d CE from C. verum for eight weeks: A significant decrease in glycosylated
hemoglobin (by 6%) and in blood TAG-levels (by 15%) compared to a placebo group
could be detected; other values like blood glucose, LDL or HDL did not change
significantly [78].
PLANT BREEDING AND BIOTECHNOLOGY
C. verum is a cross-pollinated species and wide variability has been observed in
yield, quality of harvest and oil content, along with other morphological characteristics.
The selection of high-yielding lines is performed from open pollinated seedling progenies
to take advantage of the genetic variation in the population [79]. Cinnamon is commonly
propagated through seeds. However, vegetative propagation is necessary to produce high
yielding plantations, as well as to propagate the selected elite lines and to avoid variation
in yield and quality. The tree can be propagated vegetatively through cuttings and
layering. Single node cuttings with leaves can be rooted in a month under conditions of
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high humidity. It has been shown that application of auxins IBA or IAA enhances rooting
up to 73%. [8, 80].
Conventional methods of propagation by cuttings and layering are very slow and do
not guarantee homogeneity. Hence, plant micropropagation by tissue culture represents
the ideal pathway to develop rapid and reliable methods of propagating this species
maintaining the genetic uniformity in the propagules. In vitro bud break occurred in shoot
tip explants after eight weeks on MS medium containing 1.0 mg/l BAP supplemented
with 2.5 mg/l TDZ [81]. A protocol for the in vitro propagation of C. verum through
embryo culture and axillary buds was developed culturing embryonic axis on half
strength MS medium supplemented with 1.5 mg/BAP and 0.2 mg/l IAA. The shoots
obtained from the embryo explants were successfully rooted after subculture on medium
supplemented with 0.1 mg/l NAA, 4.0 mg/l BAP and 1.0 g/l activated charcoal [82].
Molecular markers are a useful tool for the assessment of genetic variation of propagation
methods, PCR-based techniques such as Randomly Amplified Polymorphic DNA
(RAPD) and Sequence Related Amplified Polymorphism (SRAP) have been developed
for C. verum. These molecular tools have also been applied to screen accessions of
collected germplasm and to estimate the genetic diversity of the species [81, 83, 84].
DNA barcoding methods have also been successfully applied to identify C. verum and to
differentiate it from related species such as C. cassia and C. malabatrum. These methods
are useful to verify the taxonomic status of collected accessions, and also for detection of
adulteration in commercial samples of true cinnamon, which sometimes contain spurious
species [84, 85]. Since high-quality DNA is a pre-requisite for the aforementioned
molecular tools, a new protocol of DNA isolation, which can be applied to different
species of the genus Cinnamomum, has been reported. This protocol is claimed to be able
to remove the polysaccharides and polyphenols abundant in cinnamon samples and to be
used to isolate DNA from young plant leaves as well as younger tissues including
seedlings or even frozen tissue [86].
CONCLUSION
Cinnamon has been broadly commercialized because of its fragrance, aroma and
spicy flavor and is very attractive to the food industry. Sri Lanka is the major exporter of
true cinnamon (C. verum) and Mexico is the major importer in the world. The main
active components of cinnamon bark are trans-CA and eugenol, which are responsible
for its fragrance and for most of its biological activities. Many studies attributed several
beneficial biological effects to cinnamon extracts or isolated compounds, but usually in
concentrations so high that they are not achieved in human bodies when they are
consumed in small quantities as in food spice. Additionally, it should be considered that
CA is eliminated readily: when rats orally ingest 125-500 mg/kg CA once, maximal
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plasma levels of 80-250 ng/ml were reached within 1.5-2 h and with a half-life time
of ~1.7 h, CA is oxidized rapidly to cinnamate and mainly eliminated in urine as
hippurate [87, 88]. Thus, in order to achieve the observed effects, CA, eugenol, a
proanthocyanidin or even whole extracts should be consumed as nutraceuticals.
Astonishingly, several studies did not differentiate well among the different
Cinnamomum species: C. verum is the classical Ceylon cinnamon, while C. cassia is
cheaper and sold as Chinese cinnamon. Both extracts vary considerably, with C. verum
having only traces of coumarin while C. cassia has much higher amounts. Due to
hepatotoxic effects of coumarin (reviewed in [89]) the European Food Safety Authority
(EFSA) had already recommended a Tolerable Daily Intake (TDI) of 0.1 mg/kg coumarin
for humans in 2004. Thus, it is of high interest for consumers that commercial products
(as well as scientific studies) indicate precisely, which type of cinnamon was used for the
production (and study, respectively).
Those facts demonstrate the need to develop protocols for the in vitro propagation of
C. verum in order to allow the propagation of selected genotypes to establish plantations
with high-yielding clones. The reported protocols can be applied not only as rapid and
efficient plant propagation systems but also as the means to develop additional techniques
based on in vitro culture for the plant improvement of cinnamon. Moreover, the
identification and verification of the C. verum elite varieties obtained from seeds or by
clonal propagation can be achieved through molecular tools such as DNA markers or
DNA fingerprinting.
While research to date has produced a large amount of information regarding the
composition and biological activity of cinnamon essential oil, the basic knowledge of the
biosynthetic routes and the regulatory mechanisms responsible for the production of the
principal constituents is still lacking. This fundamental understanding is urgently required
to create a rational approach towards commercial production of valuable metabolites
from cinnamon by plant biotechnology.
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ABOUT THE EDITORS
Anaberta Cardador Martínez
Tecnologico de Monterrey
Escuela de Ingeniería y Ciencias
Epigmenio González
Querétaro, México
mcardador@itesm.mx
Víctor M. Rodríguez García
Tecnologico de Monterrey
Escuela de Ingeniería y Ciencias
Epigmenio González
Querétaro, México
vmrodrigg@itesm.mx
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