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REVIEW
Studies on perilla, agarwood, and cinnamon througha combination of fieldwork and laboratory work
Michiho Ito
Received: 6 March 2008 / Accepted: 30 April 2008 / Published online: 28 June 2008
� The Japanese Society of Pharmacognosy and Springer 2008
Abstract Fieldwork is one of the primary methods for
studying medicinal plants and materials, and information
thus obtained can be valuable for experiments performed in
the laboratory. Meanwhile, results of experiments in the
laboratory can be brought back to the field for verification
and further investigation. A combination of field and labo-
ratory work has led to effective progress in studies of
medicinal plants in the field of pharmacognosy. However,
the collection of samples with information through field-
work is not easy, and it fundamentally requires a great deal
of research experience. Geographical, ethnical, and politi-
cal affairs often affect its performance, and to establish a
good cooperative relationship with foreign localities is
inevitably required. Beyond these difficulties, fieldwork
can provide a framework for the research project and
excellent and unique viewpoints concerning the target. This
review article describes studies on perilla, agarwood, and
cinnamon, focusing mainly on the results of fieldwork
performed in Indochina on these species. All three of these
medicinal plants contain essential oils, and their composi-
tion varieties, biosynthetic pathways, pharmacological
activities, or induction mechanisms for production are
principally investigated through shuttling between field-
work and laboratory experiments.
Keywords Fieldwork � Perilla � Agarwood �Cinnamon � Indochina
Introduction
Perilla [Perilla frutescens (L.) Britton], agarwood (Aqui-
laria sp.), and cinnamon (Cinnamomum cassia Blume) are
natural medicines found in eastern Asia. They are primarily
used in medicinal roles and also for other secondary pur-
poses, i.e., perilla as a kitchen herb, cinnamon as a spice,
and agarwood as an incense; increasing numbers of prod-
ucts made from these plants can be found in various forms
in our daily life. Each of these plants contains fragrant oils,
the composition and content of which significantly affect
the quality and pharmacological activities of these medi-
cinal plants. However, little study has been done by
researchers in pharmaceutical sciences relating to the fac-
tors responsible for the variation and mechanisms of the
formation and accumulation of the fragrant compounds in
the plant body. In spite of their familiarity in our daily life,
these plants have not beem fully investigated either in the
field of plant taxonomy or of plant breeding, probably
because they are not main crops in agriculture. Perilla is
one of the most popular kitchen herbs in Japan, used as a
garnish for raw fish or coloring and flavoring for traditional
pickles, but it is not frequently chosen as a material for
scientific studies. Agarwood and cinnamon are timber
species native to tropical and subtropical zones of East
Asia, but do not grow in Japan. Their trunks and bark are
the parts used, so considerable periods of time are required
to complete studies on them, which may make their ana-
lysis less popular. Studies on these species of medicinal
plants, not only phytochemically, but also on their present
status in production sites, taxonomical examination, clon-
ing, and heterologous expression of biosynthetic enzymes
related to essential oil compounds and more, are under way
as part of comprehensive research based on fieldwork in
Indochina. Several years have passed since the research
M. Ito (&)
Department of Pharmacognosy,
Graduate School of Pharmaceutical Sciences,
Kyoto University, 46-29 Yoshida-Shimoadachi,
Sakyo, Kyoto 606-8501, Japan
e-mail: [email protected]
123
J Nat Med (2008) 62:387–395
DOI 10.1007/s11418-008-0262-z
project was started, and numerous interesting and novel
results have come from the study.
Research project based on fieldwork
Our research project is based on fieldwork mostly per-
formed outside Japan, and many laboratory experiments
have been developed as an outcome of the fieldwork, in
which ‘‘people,’’ ‘‘materials,’’ and ‘‘information’’ will fre-
quently come and go between the field and laboratory. In
order to reach what is required in the project, researchers
will go out to the field to come into contact with the target,
become familiar with the surrounding environment, and
gather materials and information. Raw materials and
information are brought back from the field to the labora-
tory, sorted, and employed in many types of experiments,
such as taxonomical comparisons of morphological char-
acteristics and nucleic acid sequences, phytochemical
fractionation guided by certain biological activities, or
cloning and functional expression of enzymes relating to
the biosynthesis of compounds, and so on. Accompanied
by results of this laboratory work, researchers will return to
the field for the next stage. Shuttling between field and
laboratory cycles gradually builds up a complete picture of
the target.
Many of the targets are medicinal plants, for example,
agarwood, cinnamon, clove, ephedra, or licorice, which do
not grow natively in Japan, and information derived from
imported natural medicine products made of dried parts of
the plant is the only thing available in the laboratory.
Everything starts in these cases by going to the site of their
cultivation or natural growth. While Japanese domestic
species, such as perilla, can be cultivated in the experi-
mental field next to the laboratory, so that some particular
investigations can be done using plants in the field even for
perilla fieldwork outside, Japan has brought numerous new
findings and materials for study.
A style of research based on fieldwork is frequently
employed for studies of cultural anthropology, folklore,
and ethnology, while pharmacognosy and its related fields
are probably the only research fields among pharmaceutical
sciences that can use fieldwork to their advantage. It is
unique, but mere observation in fieldwork is not enough for
project construction, and neither are laboratory experi-
ments; the best results can be obtained when they are
combined properly. Practically speaking, the collection of
samples with information through fieldwork is not easy,
and it fundamentally requires a great deal of research
experience in fieldwork. Especially fieldwork performed
overseas is very much affected by geographical, ethnical,
and political affairs, which accordingly change the actual
fieldwork protocols in each area as well as the volume and
character of information obtained from them. The target
plants are often the natural medicines merchandized in the
area as goods that local people are living on, and tips and
secrets related to production of the plants may not be easily
drawn from them by research interviews because the
researcher is a stranger in the area. It is necessary and
important to find a suitable person in the fieldwork area
who can be a partner researcher of the project and can then
perform cooperative field surveys several times within the
first few years to establish good connections with people in
the locality and at the same time to increase familiarity
with the culture and atmosphere there. These efforts will
gradually reduce local people’s feeling of wariness towards
foreign researchers and lead to greater openness in inter-
views. The significance of the information as well as the
quality of samples obtained from the site can be greatly
improved as members of the research group are accepted
into the local society. Recent trends in scientific research
are mostly pursuing quicker and easier protocols or ready-
made reagent kits that guarantee the same results in all
laboratories and a saving of time; however, contrarily
studies based on fieldwork often require many years of
efforts to gather truly important and essential facts about
the target.
Our series of research projects in Indochina started with
a field survey on Vietnamese folk medicine, which con-
sisted of two trips in 1995 [1]. Afterwards, cinnamon and
agarwood, both of which are special products of medicinal
plants in Vietnam, were set as the targets of intensive study
along with traditional and folk medicines used among
people in rural villages. As for perilla, a wide range of
studies has been done using Japanese species, though one
of the fields of studies, namely phylogenetic studies
searching for ancestral species of the cultivated species
through a chemotaxonomical approach, inevitably needs
field research outside Japan; therefore, perilla was added to
a list of target species of the project. Since 2005, the
investigation area for the project has been enlarged not
only in Vietnam, but also in Thailand and Laos, and field
surveys and experiments are performed continuously in
each area.
Perilla
Perilla (Perilla frutescens) (Fig. 1-7, 8) is probably more
familiar to Japanese people as a culinary plant than as a
medicinal plant, and its seeds (mericarps) are used like
sesame seeds. The scent of perilla is derived from essential
oils that are synthesized and accumulated in trichomes
located on both the surfaces of leaves and stems. The
varieties of scent arise from the composition of oil com-
pounds, which are dependent on genetic regulation [2].
388 J Nat Med (2008) 62:387–395
123
There are several types of oil composition, but only a type
whose main compound is perillaldehyde (PA) is recognized
as having medicinal uses in the Japanese Pharmacopoeia.
Japanese culinary perilla is also of the PA type, while this
smell seems to be preferred only by Japanese and Viet-
namese, and neither Chinese, Thai, Korean, Taiwanese, nor
mountainous Laotian people use this type, but rather use
other types, such as perillaketone (PK)- or piperitenone
(PT)-containing varieties. However, in Indochina, it is
mainly in towns and cities that perilla leaves are used as a
vegetable, and people in mountainous villages do not use
the leaves, but eat the mericarps. In Japan, food usage of
mericarps is found especially in the northern part of Hon-
shu Island, while historically it has been used for making
Fig. 1 1 Fresh and dried MN
cinnamon bark in the factory
(Tam Ky, Vietnam). 2 YB
cinnamon bark dried in the
factory (Yen Bai, Vietnam).
3 Fruits of MN cinnamon tree
(Tra My, Vietnam). 4 Dark-
colored portion of a treated
Aquilaria tree (Borai, Thailand).
5 Resinous portion of thin twigs
of a treated Aquilaria tree (Hai
Nan island, China).
6 Distillation apparatus for
agarwood oil (Borai, Thailand).
7 Perilla mericarps sold at the
market (Nam Tha, Lao PDR).
8 Perilla plants growing on
roadside of the rice field (Fang,
Thailand)
J Nat Med (2008) 62:387–395 389
123
drying oil for waterproofing umbrellas or as lamp oil.
Mountainous villagers in Indochina mainly use perilla
mericarps like sesame, and foods made with perilla meri-
carps have long been very popular in the area. For example,
mericarps are roasted and mixed into steamed sticky rice
often with cane sugar. However, recent development of
irrigation systems changed their main crop from dry-paddy
rice to paddy rice, which resulted in less cultivation of
perilla because perilla in this area is mostly cultivated
mixed with dry-paddy rice, and dampish paddy rice fields
are not suitable for the cultivation of perilla. In addition,
sesame seems to have replaced perilla as a more mer-
chandisable crop [3].
The morphological characteristics of perilla plants cul-
tivated for using mericarps are different from that of plants
for leaf use, which are supposed to have been established
by an extensive breeding for selecting larger grains with
thinner pericarps that could be suitable for food usage. On
the other hand, characteristics of leaf scent, in other words,
the composition of essential oil, are not likely to have been
an index for breeding, which accordingly left the plants
almost free from selection bias with regard to oil types;
therefore, it is interesting to analyze oil type variation of
these varieties. Actually, a new oil type, which consists
mainly of piperitenone and related cyclohexene-type
compounds (PT type), was found among mericarp samples
collected in northern Thailand [4]. In addition, recent
samples from Laos were found to include an oil type that
contains significant amounts of a putative intermediate for
furan ring-bearing compounds [3].
There are two main groups among the oil types of
perilla; one is a monoterpenoid type, which includes types
of PA, PT, PK, elsholtziaketone (EK), perillene (PL), shi-
sofuran (SF), and citral (C), and the other is the
phenylpropene (PP) type, which harbors several sub-types
[5]. Strict genetic control of these types is observed [6], and
dominancy between the types could be analyzed by
crossing experiments; pure strains of perilla that had been
bred by successive self-pollination, which was affirmed by
bagging flowers just before they open every year, were
employed for crossing experiments between different oil
types to determine the number of loci functionally regu-
lating the expression of the types. It usually takes 3 years
to determine one locus that corresponds to a characteristic.
Our recent studies were mainly focused on the molecular
cloning of enzymes for oil compound synthesis that were
considered to correlate with these loci. Generally, mono-
terpene compounds of essential oils are formed from
geranyl diphosphate (GDP) with the initial removal of the
pyrophosphate portion by the synthase, and then oxidized,
hydroxylated, or further cyclized by a P450-cytochrome-
dependent enzyme and/or other oxygenase to be converted
into various oil compounds. Since the monoterpene
principles of perilla oil are of two types, cyclohexene and
furan-ring types, their synthetic enzymes have been pro-
posed to be a limonene synthase and a geraniol synthase,
respectively. A limonene synthase from a mint species has
already been cloned by Croteau’s laboratory [7], and a PA-
type perilla homologue was cloned using the mint limo-
nene synthase as a probe for cDNA library screening [8].
Recently, geraniol synthases of perilla were cloned through
a RACE (rapid amplification of cDNA ends) method by
designing primers against the conserved DDXXD motif
sequence [9]. In particular, the sequences of geraniol syn-
thases that were cloned from the cultivated species,
P. frutescens, and the wild species, P. citriodora, are very
similar, which supports our hypothesis that the cultivated
species of perilla was developed as an amphidiploid of the
wild species [9]. Molecular cloning of the enzymes con-
cerned with the biosynthesis of oil compounds is important
to clarify the pathway of secondary metabolites, but it is
also of interest for investigations into the phylogenetic
relationship between species and strains and to determine
the ancestral species of perilla. Future studies will pursue
enzymes concerned with furan ring formation and the
synthesis of phenylpropene compounds.
Perilla plants for medicinal and culinary use are all the
cultivated species, P. frutescens, which has 2n = 40
chromosomes, while the wild species of the same genus
have 2n = 20 chromosomes. Three Japanese wild species
are listed, and several oil types are found among them, such
as those in the cultivated species; however, the variety of
oil types found within a group is different among species
[5, 10]. One of the wild species, P. citriodora (Makino)
Nakai, shares many oil types with the cultivated species,
and its distribution ranges from Japan and Taiwan to
southern China. Furthermore, with the following results
that the morphological characteristics of young inflores-
cences of P. citriodora resemble most closely those of the
cultivated species rather than those of other wild species
[10], ten bivalent chromosomes were observed in the
microscopic section of mitotic metaphase pollen mother
cells of the F1 plant between P. frutescens and P. citriodora
[11]. In addition, the patterns of RFLP (restricted fragment
length polymorphism) and RAPD (randomly amplified
polymorphic DNAs) showed P. citriodora was the most
closely related to cultivated species [12], and the sequences
of geraniol synthases expressed in P. frutescens and in
P. citriodora were almost identical, not only for the coding
regions, but also for the non-coding regions [9]. Therefore,
we propose that the cultivated species of perilla was
formed as an amphidiploid of two wild species, one of
which was P. citriodora. The other putative parental wild
species of the amphidiploid is unknown; therefore, one of
the main purposes of our fieldwork on perilla is searching
for candidates for the ancestral wild species of cultivated
390 J Nat Med (2008) 62:387–395
123
perilla. More results of experiments are described else-
where [13].
Occasionally, considerable amounts of fossilized perilla
mericarps are discovered in the ruins of Johmon era (ca.
10,000–400 BC) settlements [14], which are almost always
found with fossilized rice grains. This might suggest that
ancient people who had started cultivation of rice, probably
a dry-paddy rice, already recognized that perilla mericarps
were edible and raised them together in their fields. This
custom of growing perilla with dry-paddy rice has been
continued till now in the mountainous villages in Indo-
china. Though our research project is based in the field of
pharmaceutical sciences, not agriculture or ethnobotany,
studies based on fieldwork frequently extend outside their
original field. This integrated aspect of studies must be one
of the most unique and attractive parts of pharmacognosy
when it is based on fieldwork.
Agarwood
Agarwood (Fig. 1-4, 6) is a kind of natural medicine
mixed into a number of traditional oriental prescriptions,
such as ‘‘Rokushin-gan ( )’’ or ‘‘Kiou-gan ( )’’,
but it is most widely used as an incense wood. Pieces of
agarwood of the highest quality are especially distin-
guished and called ‘‘Kyara ( )’’ in Japanese. Pieces of
Kyara are an important material for Japanese traditional
incense ceremonies, where participants try to distinguish
several pieces of Kyara by inhaling the subtile fragrance
rising from each warmed piece. Agarwood is also used in
Indochina as a blending material for high-quality stick
incense and has been produced mainly in Vietnam as a
special product of the area. However, probably because
agarwood has always been a very expensive product that
particular peoples collected in the mountains and brought
to towns, there is very little information available on its
production. The method of production and how to find
and collect agarwood in woods seem to be secrets that are
never disclosed by people of these localities. In the year
2000, when our project was started in Vietnam, Aquilaria
trees were not very well known even in the research sites,
though these trees have flourished recently in Vietnam,
Thailand, and some other places in Indochina as one of
the most profi-
table plants. Wild Aquilaria trees as well as other agar-
wood-producing species were all included into the list of
CITES (Convention on International Trade in Endangered
Species of Wild Fauna and Flora) Appendix II in 2005
and since then have been strictly inspected and controlled
by the governments of their countries of origin when they
are exported and imported. Agarwood has become a
famous and topical product in Indochina.
Particular species of Thymeraeaceae belonging to
Aquilaria, Gonistulus, Gyrinops, and some other species
are known to be the origins of agarwood. Resin is accu-
mulated in the dying trunks and branches, but not at all in
fresh and healthy trees; resinous compounds consisting of
fragrant sesquiterpenes and unique chromones are accu-
mulated in wounded or withered parts, especially where
living cells and dying cells occur mixed together. This
resin production can be mimicked experimentally on a
miniature scale by making holes or sticking pushpins and
nails onto the trunks of Aquilaria trees grown in the
greenhouse, which led us to identify epoxychromones and
syringaresinoles that were initially formed in the course of
resin production [15]. It was also found using the mimic
resin production system that sesquiterpene compounds
formed by artificial wounding were of the guaian type,
whereas agarwood of the highest grade contains much
higher amounts of the eudesman type. Both types of ses-
quiterpenes are supposed to be derived from FPP (farnesyl
pyrophosphate), though the formation of each compound is
catalyzed by different enzymes. This implies that the
condition of artificial wounding and of natural agarwood
formation are definitely different, and the induced meta-
bolic enzymes are different. Induction of resinous
compound formation by certain stimuli was also observed
for cultured cells of Aquilaria species, where methyl
jasmonate and other chemical substances, which have been
reported as inducers of defensive secondary metabolism,
are applied instead of physical wounding [16].
These experiments on plants and cultured cells could be
the basis of studies of artificial agarwood production
through trying to clarify the mechanisms of biosynthesis of
resin as well as its inducibility. Good results from such a
study might be of substantial value for the local production
of agarwood, which would be an example of a reward for
local cooperation. Research projects including fieldwork
are interesting and unique in this aspect as its management
requires the local people’s cooperation and at the same
time rewards their efforts; scientific impact factors or
counting of papers are not of absolute importance for the
project. This character of the study might be very different
from that of other fields of pharmaceutical sciences, but
hopefully can be understood generally.
Trees of agarwood-producing species can be cultivated
rather easily in tropical and sub-tropical climates; however,
accumulating resin in their trunks is very difficult, and
many attempts to achieve it have failed. The white and
porous wood without resin is useless and cannot even be
used as timber for building houses. Therefore, it is urgently
required that the local people develop the best method of
accumulating high-quality resin in cultivated agarwood
trees within a short period. An American researcher devised
a means of producing fragrant compounds in the trunks of
J Nat Med (2008) 62:387–395 391
123
Aquilaria trees and took out a patent for the method in the
USA (US patent no. 6848211); pipes of chlorinated vinyl
are stuck into the trunks, and a special liquid is injected
through the pipes into the tree trunks to induce the pro-
duction of fragrant compounds. An agarwood seller in
Thailand has developed a method of producing agarwood
for distillation by injecting a special mix of clay into holes
drilled in Aquilaria trunks, and he has already started pro-
duction of agarwood oil using materials obtained by his
method. Our experimental trials for making resin are based
on information from these studies and that collected by
interviews with local people, though neither the patented
American method nor the local Thai method could produce
better agarwood than natural sources. These artificial
methods yield a dark-colored, soft, and fragile portion of
Aquilaria tree trunks containing sesquiterpene and chro-
mone compounds, but its fragrance and characteristics are
somewhat different from the material called ‘‘Jinkoh ( )’’
in Japanese. These fragrance-containing portions could not
be used for the Japanese traditional incense ceremony.
However, these methods are welcomed by local people
because these agarwoods can be used as materials for oil
distillation. Agarwood oil is an expensive and famous
blending material for fragrant balms in the Middle East,
especially among wealthy people of petroleum-producing
countries, even to the point of coming to mountainous
agarwood-oil factories in Indochina carrying US dollars in
suitcases to buy agarwood oil. The price of agarwood and
its distilled oil have been rising drastically since all species
of agarwood-producing trees were listed as endangered, so
that any kind of agarwood, even of a low-grade and less-
resinous pieces, are collected and sold, which consequently
seems to be accelerating the exhaustion of agarwood.
However, through our repeated field surveys, we have come
to understand that the required attributes of agarwood used
for oil distillation and those for the Japanese incense cer-
emony are completely different. This is because the incense
ceremony is a Japanese original tradition that people in
Indochina are not familiar with, so they do not know what is
suitable for the ceremony, and agarwood is one of the few
agricultural products that is expected to generate a good
retail price to reward the localities. This means that local
people want to harvest agarwood as much as poaaible
within a short cultivation time, and these products are used
for oil distillation. Interviews with local people revealed
that planted trees of Aquilaria sp. in Indochina are mostly
cultivated for 3–5 years, treated by various methods in
order to produce resinous compound in the trunks, and
finally harvested within 5–8 years and cut into pieces for
distillation.
In the laboratory, phytochemical analyses and pharma-
cological studies of local varieties of agarwood oils as well
as its isolated constituents are under way. Neither agarwood
nor its distilled oil is officially listed in the Japanese Phar-
macopoeia, so no standard for quality control has been
determined up to now. Composition analyses of oils
revealed a wide range of varieties, but their retail price does
not always correspond to quality differences. Sometimes
the main component of the oil turned out to be an unex-
pected compound that had never been reported as a
principal of agarwood resin, but was instead a principal of
another Labiatae herb; this supposedly occurred due to
blending of essential oils other than agarwood in order to
increase its volume. Adulterated products of agarwood
seem to be on the increase as the inflation of agarwood
prices accelerates. These agarwood oils, especially those
containing abundant sesquiterpene compounds of eudes-
mane and guaiane types, were used for our pharmacological
assays. Agarwood oils were administered to mice by natural
breathing, and compounds from the natural oil had a strong
behavior-restraint effect on mice. Further studies with a
combination of phytochemical and pharmacological
experiments revealed low-molecular-weight active sub-
stances, such as calarene, benzyl acetone, and valerian-
4,7,(11)-dien, in the oils [17]. The olfactory sense, foremost
among the five senses of humans, is supposed to be the most
closely related to one’s recall of experiences and has been
investigated by many researchers. However, the above-
mentioned behavior-restraint activity observed in mice is
supposed to be independent of experience, but is probably
caused by compounds absorbed via nasal and lung mucous
membranes into the blood stream. This activity might be
capable of treating ADHD (attention deficit hyperactivity
disorder) by non-obtruding administration by natural
breathing.
Agarwood had barely been studied prior to our research
project in Indochina. Repetition of our field surveys and
accumulation of years of knowledge on cultivation in the
greenhouses of our campus have been combined with
experiments in laboratories and gradually revealed the
reality of agarwood. However, taxonomical information on
the species is still not perfect, and what influences the
different amount of resin and quality of fragrance in each
piece of agarwood, namely, whether it is dependent on the
plant species or the induction process, is uncertain [18]. In
order to understand what makes the best agarwood, we
need further investigations on plant physiological mecha-
nisms of resin production in the wood as well as the
fundamental plant taxonomy of agarwood-producing
species.
Cinnamon
Cinnamon (Fig. 1-1, 3) is more commonly used as spice and
flavoring for food and drinks than as a medicine, and 90%
392 J Nat Med (2008) 62:387–395
123
of consumption in Japan is for food stuffs. However, cin-
namon is a very important medicinal plant, which is
included in many Kampo prescriptions and also as an aro-
matic stomachic for over-the-counter sale. Cinnamon
powder used for spice is made from the bark of Cinnamo-
mum burmannii (Nees & T. Nees) Blume, C. cassia (=C.
aromaticum Nees), or C. zeylanicum Blume (=C. verum J.
Presl), while the source plant species for Cinnamomi Cortex
in the Japanese Pharmacopoeia is solely designated as
C. cassia. The bark of C. zeylanicum bears a particular
fragrance derived from a mixture of cinnamaldehyde and
considerable amounts of eugenol, and European people
seems to prefer this type. Our research targeted the varieties
of C. cassia, the sort of cinnamon authorized for medicinal
use by the Japanese Pharmacopoeia; however, scientific
research, especially concerning biological aspects of source
plants and production processes, have not been performed
frequently up to now, although large amounts of cinnamon
are consumed both for medicinal and food stuff use. The
production site of cinnamon (C. cassia) is particularly
restricted to southern China and Vietnam, and cinnamon
has long been known as a special product of Vietnam.
People in Vietnam have been producing cinnamon since
ancient times, and they clearly distinguish cinnamon
products from northern and southern areas. How different
were they and what makes them different were the first
simple questions that caused us to launch the research
project.
Vietnam has two main production places for cinnamon.
One is in the northern area where Yen Bai and its neigh-
boring districts produce YB cinnamon, and the other is in
the southern area around the Quan Nam district, and its
products are called MN cinnamon [19]. The source plant
species for cinnamon from both areas are supposed to be
C. cassia, though the tastes of these two cinnamons are
fairly different; YB cinnamon has a strong pungent taste,
and MN is much more sweet. Repeated visits to the pro-
duction places and many interviews with local people in
the areas gradually unveiled their distinctive characters.
YB cinnamon. The history of cinnamon cultivation in
Yen Bai and its neighboring district is very long, so that the
mountains in the production area are almost all covered by
pure forests of cinnamon trees. Commercial cinnamon
products in this area are all made from cultivated trees, and
none are from wild trees. The cinnamon trees are cultivated
according to a well-organized plan that has been estab-
lished over the long history of cultivation in this area. Trees
are cut at their base when they are harvested to peel bark
off, and residual roots in the soil are also dug out for new
seedlings to be planted. Another method of harvesting,
which leaves the base part of the trees with roots and
several new shoots coming out from the residual thick
trunk to be grown for the next harvesting, is commonly
performed in China. However, in Vietnam, this method has
not been adopted because people in Vietnam believe the
former method produces better cinnamon. Seeds of cin-
namon trees for cultivation are collected in their own forest
and germinated nearby. Thin barks for exporting to India
are harvested from trees of 5- to 7-years old, and thick
barks to be made into tube-type cinnamon are from
10-year-old trees. April to October is the season for peeling
bark off the trees, and the most intensive period is at the
end of April. Trees in mountainous areas are, in most cases,
owned and taken care of by individual families. Peeled
fresh bark is sold to brokers by weight and then transferred
to processing factories to be dried, classified, cut, and
packed in boxes according to customer requests. High-class
products made from more than 25-year-old trees have been
produced in the past, but recently have not been common in
the area. Most of the cinnamon bark produced in the YB
area now is tube-type cinnamon made from 8- to 10-year-
old trees. YB cinnamon is very famous worldwide for its
excellent quality, so that special commercial promotion for
sale seems not to be required, and the product is dispatched
for domestic sale as well as exported to Taiwan, Korea,
India, and Japan.
MN cinnamon. The code name ‘‘MN’’ originates from
an old name for the area, Minh Nam, which means
southern area. Cinnamon trees grown in this area are called
Tra My type, which is a form native to southern Vietnam,
while the northern cinnamon forma is called Than Hoa
type. Since Tra My and Than Hoa types differ in many
characteristics, they are strictly distinguished in Quan Nam
province. Than Hoa type trees grow much faster than the
Tra My type, so the farmers have introduced the Than Hoa
type actively in the past. However, although the trees are
raised in the same area under the same conditions and with
the same care, the Tra My type bears far better oily bark, so
its products bring much better prices. Nowadays, Than Hoa
type trees are not allowed to be planted anew in Quan Nam
province. These two types are almost the same in mor-
phological characteristics, but the adaxial surface color of
leaves, taste of the petiole, and surface appearance of the
bark are somewhat different between them. These charac-
teristics are stable differences and are shown clearly when
these two types are planted at the same site. As in the north,
cinnamon trees on the mountains are owned and taken care
of by families, especially for mountainous minority tribes
in the MN area. Cinnamon trees in this area are a kind of
property for these minority people, and whether they har-
vest cinnamon or not in a season as well as how much they
sell are dependent on how much money they need at the
time. In particular, for occasions such as a marriage or the
birth of a child that require more money than usual, they
plan to harvest bark to sell. There are also big plantations
of cinnamon run by businessmen. Some plantation owners
J Nat Med (2008) 62:387–395 393
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operate processing factories where raw material of cinna-
mon bark from both their own plantations and from other
growers are gathered. Thick barks of excellent quality are
formed into ‘‘M’’ shape, which can be made exclusively
from oil-rich bark, and further processed by scraping the
outer cortex off according to the customer’s request. These
high-class products are made from bark of at least 20-year-
old trees and normally from 30- to 40-year-old trees. Pro-
cessed and dried cinnamon barks are classified and packed
for shipping abroad as well as for domestic sale. The leaves
of these cinnamon trees also contain large amounts of oil
that can be extracted by distillation, though recent market
demand for leaf oil has fallen, and manufacture stopped
several years ago. The largest customer of MN cinnamon is
Taiwan, which is followed by Vietnamese domestic
customers.
The taste of cinnamon consists of both sweet and
pungent elements; qualified cinnamon powder gives a
sweet taste at the beginning and then a strong piquant
taste follows. This double-phased taste of cinnamon is
known to be stronger as its oil content increases, but
which compound is responsible for each taste is not clear.
It seems that many people expect the pungent taste to
come from cinnamaldehyde, while the source of the sweet
taste has been in question since cinnamon bark does not
contain much glucose or fructose. There is a sort of
tannin in the bark of C. zeylanicum that has a sweet taste,
but this compound has not yet been reported from bark of
C. cassia. However, we found that cinnamaldehyde, the
major component in cinnamon oil, gives both sweet and
pungent tastes; cinnamaldehyde was revealed to be a
single compound contained in a fraction of sweetness
derived from sweet leaves of a certain species of Cin-
namomum growing in Taiwan (data not shown). This
sweetness of cinnamaldehyde was reminiscent of the roots
of C. sieboldii Meisn, a common species of cinnamon in
Japan, which has a sweet taste. This species contains
cinnamaldehyde exclusively in the roots. However, the
difference in taste between YB and MN cinnamon
barks—YB is pungent and MN is more sweet—might be
described as depending on whether MN cinnamon con-
tains a group of tannins or other kinds of compounds that
mask the pungent taste of cinnamaldehyde or whether YB
cinnamon contains those that mask the sweet taste, since
the content of cinnamaldehyde in the two is not especially
different. Further analyses on what makes the difference
in the proportional balance of tannin and cinnamalde-
hyde—whether from the source plant species or any
environmental factors related to the growing sites—is still
under investigation. The taxonomy of Cinnamomum spe-
cies is said to be very difficult even for professional
taxonomists and requires further discussion based on a
composed field of studies.
Future studies
In this report, I mostly described the results on perilla,
agarwood, and cinnamon obtained directly from fieldwork
being performed outside Japan. Fieldwork abroad generally
consumes a large portion of researcher’s energy in getting
funding for the project, special preparation, and project
performance, though much more time could be spent on
experiments in laboratories than in the field, and more
opportunities for publishing scientific papers are actually
given by the results from bench-top work than those from
fieldwork. However, because fieldwork on the target is
combined with laboratory experiments, a further under-
standing of the research target can be made available, and a
novel and unique viewpoint can be given. Fieldwork more
or less forms a framework of the research project that often
stretches beyond the boundaries of research fields; as for
studies in pharmacognosy, there are wide areas of cross-
over with the fields of agriculture and ethnobotany, and
these sometimes look inevitably interesting and are often
essential for further understanding of the target, though our
ultimate research goal should be within the field of phar-
maceutical sciences.
Acknowledgments I would like to express my sincere thanks to the
local people and researchers in Vietnam, Thailand, Taiwan, and Laos
who cooperated with us to achieve the field studies. My appreciation
is also expressed to the Japanese researchers and students who worked
with on these projects. My special thanks also go to Professor Gisho
Honda of Himeji Dokkyo University (emeritus Professor of Kyoto
University).
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