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Current Trends in Biotechnology and Pharmacy
Vol. 9 (3) 293-304 July 2015, ISSN 0973-8916 (Print), 2230-7303 (Online) 294
Abstract
Secondary metabolites (SM) are
compounds that are not necessary for a cell
(organism) to live, but play a role in the interaction
of the cell (organism) with its environment. These
compounds are often involved in plants protection
against biotic or abiotic stresses. Secondary
metabolites are from different metabolites
families that can be highly inducible in response
to stresses. Primary metabolites perform
essential metabolic roles by participating in
nutrition and reproduction. A few SMs are used
as especially chemical such as drugs, flavours,
fragrances, insecticides, and dyes and thus have
a great economic value. These new technologies
will serve to extend and enhance the continued
usefulness of the higher plants as renewal
sources of chemicals, especially medicinal
compounds. A continuation and intensification
efforts in this field is expected to lead to
successful biotechnological production of
specific, valuable and as yet unknown plant
chemicals.
Keywords: Secondary metabolites, drugs,
flavours, fragrances, biotechnology
Introduction
Plants possess capacity to synthesize
different organic molecules called secondary
metabolites. Unique carbon skeleton structures
are basic properties of plant secondary
metabolites. Secondary metabolites are not
necessary for a cell (organism) to live, but play a
role in the interaction of the cell (organism) with
its surroundings, ensuring the continued
existence of the organism in its ecosystems.
Formation of SMs is generally organ, tissue and
cell specific and these are low molecular weight
compounds. These compounds often differ
between individuals from the same population
of plants in respect of their amount and types.
They protect plants against stresses, both biotic
(bacteria, fungi, nematodes, insects or grazing
by animals) and abiotic (higher temperature and
moisture, shading, injury or presence of heavy
metals). SMs are used as especially chemical
such as drugs, flavours, fragrances, insecticides,
and dyes by human because of a great economic
value.
In plants, SMs can be separated into three
groups (Terpenoids, Polyketides and
Phenypropanoids) based on their biosynthesis
origin (1). Alkaloids are additional class of SMs,
which are nitrogenous organic molecules
biosynthesized mainly from amino-acids, e.g.,
tryptophan, tyrosine, phenylalanine, lysine and
arginine using many unique enzymes (2). Many
of the most important therapeutic agents are
alkaloids. The sites of biosynthesis are
compartmentalised at cellular or sub-cellular
level. However SMs can be transported long
distances and accumulate from their location of
synthesis.
Primary Vs Secondary Metabolites : Primary
metabolites are found in all plants and execute
vital metabolic responsibilities, by participating in
Secondary Metabolites of Plants and their Role:
Overview
Saurabh Pagare1*, Manila Bhatia1, Niraj Tripathi2, Sonal Pagare3 and Y.K. Bansal1
1Department of Biological Science, Rani Durgavati Vishwavidyalaya,
Jabalpur (M.P.)-482001, India
2Directorate of Weed Science Research, Jabalpur (M.P.)-482004, India
3NTPC Hospital,Korba (C.G.)-495450, India
*For Correspondence - saurabhhind@gmail.com
Secondary Metabolites of Plants and their Role
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Current Trends in Biotechnology and Pharmacy
Vol. 9 (3) 293-304 July 2015, ISSN 0973-8916 (Print), 2230-7303 (Online) 295
nutrition and reproduction (2). Sometimes it is
hard to discriminate primary and secondary
metabolites. For example, both primary and
secondary metabolites are found among the
terpenoids and the same compound may have
both primary and secondary roles. Secondary
metabolites are broad range of compounds from
different metabolite families that can be highly
inducible in stress conditions. Carotenoids and
flavonoids are also involved in cell pigmentation
in flower and seed, which attract pollinators and
seed dispersers. Therefore, they are also
involved in plant reproduction (3). Plant primary
products refer to the compounds of nucleic acids,
proteins, carbohydrates, fats and lipids and are
related to structure, physiology and genetics,
which imply their crucial role in plant
development. In contrast, secondary metabolites
usually take place as minor compounds in low
concentrations. Primary metabolism refers to the
processes producing the carboxylic acids of the
Krebs cycle. Secondary metabolites, on the other
hand, are non-essential to life but contribute to
the species’ fitness for survival. In fact, the
specific constituents in a certain species have
been used to help with systematic determination,
groups of secondary metabolites being used as
markers for botanical classification
(chemotaxonomy). Plants secondary metabolites
can be divided into three chemically distinct
groups viz: Terpenes, Phenolics, N (Nitrogen) and
S (sulphur) containing compounds.
I)Terpenes : Terpenes comprise the biggest
group of secondary metabolites and are free by
their common biosynthetic origin from acetyl-coA
or glycolytic intermediates. An immense bulk of
the diverse terpenes structures produced by
plants as secondary metabolites that are
supposed to be concerned in defense as toxins
and feeding deterrents to a large number of plant
feeding insects and mammals. Terpenes are
divided into monoterpenes, sesquiterpenes,
diterpene, Triterpenes and polyterpenes. The
pyrethroid (monoterpenes esters) occur in the
leaves and flowers of Chrysanthemum species
show strong insecticidal responses to insects like
beetle, wasps, moths, bees, etc and a popular
ingredient in commercial insecticides because
of low persistence in the environment and low
mammalian toxicity. In Gymnoperms (conifers)
á-pinene, â-pinene, limonene and myrecene are
found. A number of sesquiterpenes have been
till now reported for their role in plant defense
such as costunolides are antiherbivore agents
of family composite characterized by a five
member lactone rings (a cyclic ester) and have
strong feeding repellence to many herbivorous,
insects and mammals. ABA is also a
sesquiterpene plays primarily regulatory roles in
the initation and maintenance of seed and bud
dormancy and plants response to water stress
by modifying the membrane properties and act
as a transcriptional activator (4). Abietic acid is a
diterpene found in pines and leguminous tress.
It is present in or along with resins in resin canals
of the tree trunk . Another compound phorbol
(Diterpene ester), found in plants of
euphorbiaceae and work as skin irritants and
internal toxins to mammals. The milkweeds
produce several better tasting glucosides
(sterols) that protect them against herbivors by
most insects and even cattle. Several high
molecular weight polyterpenes occur in plants.
The principal tetraterpenes are carotenoids
family of pigments.
(II) Phenolic compounds : Plants produce a
large variety of secondary products that contain
a phenol group, a hydroxyl functional group on
an aromatic ring called Phenol, a chemically
heterogeneous group also. They could be an
important part of the plants defence system
against pests and disease including root parasitic
nematodes (5). Elevated ozone (mean 32.4ppb)
increased the total phenolic content of leaves and
had minor effects on the concentration of
individual compounds (6).Coumarin are simple
phenolic compounds widespread in vascular
plants and appear to function in different
capacities in various plant defense mechanisms
against insect herbivores and fungi. They derived
from the shikimic acid pathway, common in
bacteria, fungi and plants but absent in animals
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Vol. 9 (3) 293-304 July 2015, ISSN 0973-8916 (Print), 2230-7303 (Online) 296
(7). Some coumarin derivatives have higher anti-
fungal activity against a range of soil borne plant
pathogenic fungi and exhibit more stability as
compared to the original coumarin compounds
alone (7). Furano is Also a type of coumarin with
special interest of phytotoxicity, abundant in
members of the family umbelliferae including
celery parsnip and parsley. Psoraline, basic linear
furacoumarin, known for its use in the treatment
of fungal defence and found very rarely in SO2
treated plants (8). Ligin is a highly branched
polymer of phenyl- propanoid groups, formed
from three different alcohols viz., coniferyl,
coumaryl and synapyl which oxidized to free
radical (ROS) by a ubiquitous plant enzyme-
peroxidises, reacts simultaneously and randomly
to form lignin. Its physical toughness deters
feeding by herbivorous animals and its chemical
durability makes it relatively indigestible to
herbivorous and insects pathogens. Lignifications
block the growth of pathogen and are a frequent
response to infection or wounding. Flavanoids
perform very different functions in plant system
including pigmentation and defence. Two other
major groups of flavanoids found in flowers are
flavanones and flavanols function to protect cell
from UV-B radiation because they accumulate
in epidermal layers of leaves and stems and
absorb light strongly in the UV-B region while
letting visible (PAR) wavelengths throughout
uninterrupted (9). In addition exposure of plants
to increased UV-B light has been demonstrated
to increase the synthesis of flavanones and
flavanols suggesting that flavanoids may offer
measures of protection by screening out harmful
UV-B radiation (6). Isoflavanoids are derived from
a flavanones intermediate, naringenin,
ubiquitously present in plants and a play a critical
role in plant developmental and defence
response. They secreted by the legumes and play
an important role in promoting the formation of
nitrogen fixing nodules by symbiotic rhizobia (10).
Moreover, it seems that synthesis of these
flavanoids is an effective strategy against reactive
oxygen species (ROS). The analysis of activity
of antioxidant enzymes like SOD, CAT, POX,
APX, GPX and GR suggested that peroxidases
were the most active enzymes in red cabbage
seedlings exposed to Cu++ stress (11).Tannins
included in the second category of plant phenolic
polymers with defensive properties. Tannins are
general toxins that significantly reduce the growth
and survivorship of many herbivores, and also
act as feeding repellents to a great diversity of
animals.
(III) Sulphur containing secondary
metabolites: They include GSH, GSL,
Phytoalexins, Thionins, defensins and allinin
which have been linked directly or indirectly with
the defence of plants against microbial pathogens
(12,13,14). GSH is the one of the major form of
organic sulphur in the soluble fraction of plants
and has an important role as a mobile tool of
reduced sulphur in the regulation of plant growth
and development and as a cellular antioxidants
in stress responses (15), reported as a signal of
plant sulphur sufficiency that down regulates
sulphur assimilation and sulphur uptake by roots.
GSL is a group of low molecular mass N
(nitrogen) and S (sulphur) containing plant
glucosides that produced by higher plants in order
to increase their resistance against the
unfavourable effects of predators, competitors
and parasites because their break down products
are release as volatiles defensive substances
exhibiting toxic or repelient effects for example,
mustard oil glucosides in cruciferae and allyl cys
sulfoxides in alllum (16). They are metabolised
and absorbed as isothiocyanates that can affect
the activity of enzymes involved both in the
antioxidant defence system and in the
detoxification from zenobiotics abd significantly
affect GST activity and cell protection against
DNA damage (17) whereas toxicity of
glucosinolatic products is well documented but
their mode of action has not yet been elucidated
and results from experiments with Brassica
plants modified in GSL content generated doubts
about their contribution to plant defences.
Phytoalexins are synthesized in response
to bacterial or fungal infection or other forms of
stress that help in limiting the spread of the
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invading pathogens by accumulating around the
site of infection, appears to a common
mechanism of resistance to pathogenic microbes
in a wide range of plants. Many of these changes
are linked to a rapid apoptotic response, resulting
in death of one or a few invaded plant cells,
known as the hypersensitive response (HR).
Most plant families produce organic phytolexins
of diverse chemistry; these groups are often
associated with a family, for example
sesquiterpenoids of Solanaceae, isoflavonoids
of Leguminosae, while phytoalexins from
Brassica have an indole or related ring system
and one S atom as common structural features.
Crucifereae appears to be the only plant family
producing these S metabolites, which are clearly
different from the other well- known
GSL.Cruciferous crops are cultivated worldwide
because they are extremely valuable and for the
last decades, various research groups have
investigated cruciferous phytoalexins as well as
their biological activity.Typically, there are multiple
responses involving several related derivatives
such as up to nine wyerone (Furano-acetylenic
derivatives) forms in Vicia fava and several forms
of phaseollin in Phaseolus vulgaris and glyceollin
in Glycine max, postin in Pisum sativum pods,
Ipomearone in sweet pototo, orchinol in orchid
tubers, trifolirhizin in red clover. Defensins,
thionins and lectins are S-rich non-storage plant
proteins synthesize and accumulate after
microbial attack and such related situations. They
inhibit growth of a broad range of fungi.
Additionally defensins genes are partly pathogen-
inducible and others that are involved in
resistance can be expressed constitutively. Some
plant species produce lectins as defensive
proteins that bind to carbohydrates or
carbohydres containing proteins.
(IV) Nitrogen containing secondary
metabolites: They include alkaloids, cyanogenic
glucosides, and non-proteins amino-acids. Most
of them are biosynthesized from common amino-
acids. Alkaloids found in approximately 20% of
the species of vascular plants, most frequently
in the herbaceous dicot and relatively a few in
monocots and gymnosperms. Generally, most of
them, including the pyrrolizidine alkaloids (PAs)
are toxic to some degree and appear to serve
primarily in defense against microbial infection
and herivoral attack. Cyanogenic glucosides
constitue a group of N-containing protective
compounds other than alkaloids, release the
poison HCN and usually occur in members of
families viz., Graminae, Roosaceae and
leguminosesae. They are not themselves toxic
but are readily broken down to give off volatile
poisonous substance like HCN and volatile H2S
when the plant crushed; their presence deters
feeding by insects and other herbivorous such
as snails and slugs. Amygdalin, the common
cynogenic glucoside found in the seeds of
almonds, apricot, cherries and peaches while
Dhurrin, found in Sorghum bicolar.
Many plants also contain unusual amino acids
called non-protein amino-acids that incorporated
into proteins but are present as free forms and
act as protective defensive substance. For
examples, canavanine and azetidine-2 carboxylic
acid are close analogs of arginine and proline
respectively. They exert their toxicity in various
ways. Some block the synthesis of or uptake of
protein amino acid while others can be mistakenly
incorporated into proteins. Plants that
synthesized non-protein amino acid are not
susceptible to the toxicity of these compounds
but gain defence to herbivorous animals, insects
and pathogenic microbes.
Transport, Storage and Turnover: SMs can
be water soluble (hydrophilic) compounds or
lipophilic (needs organic solvents), therefore
needs different cellular mechanism for their
transport, storage and turnover. Most substances
are synthesized in the cytoplasm, the ER or in
the organelles. Hydrophilic SMs are usually
stored in the vacuole after their formation in
cytoplasm, whereas lipophilic substances are
sequestered in resin ducts, laticifers, glandular
hairs, trichomes, thylakoid membranes or on the
cuticle. Hydrophilic SMs have to pass the
tonoplast, which is impermeable to many of the
polar secondary metabolites. For some alkaloids
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and flavanoids, a specific transporter has been
described, which pumps the compounds into the
vacuole. In order to avoid autotoxicity, plants
cannot store these compounds in the vacuole
but usually sequester them on the cuticle, in dead
resin ducts or cells which are lined by a
biomembrane but an impermeable solid barrier.
In many instances, the site of biosynthesis is
restricted to a single organ such as roots, leaves
or fruits, but an accumulation of the
corresponding products can be detected in
several other plant tissues. Long distance
transport must take place in these instances. The
xylem or phloems are likely transport routes but
an apoplastic transport can also be involved.
Storage can also be tissue and cell- specific,
depending upon the protection providing to the
plants.In a number of plants, specific idioblasts
have been detected that contain tannins,
alkaloids or glucosinolates. More often, SMs are
concentrated in trichomes or glandular hairs
(many terpenoids in Labiatae, Asteraceae),
stinging hairs (many amines in urticaceae) or the
epidermis itself (many alkaloids, flavanoids,
anthocyanins, cynogenic glycosides, coumarins,
etc.) flowers, fruits and seeds are usually rich in
SMs, especially in annual plants. In perennial
species, high amounts of SMs found in bulbs,
roots, rhizomes and the bark of roots and stems.
It is well-established that profiles of SMs vary with
time, space and developmental stage. Since
related plant species often show similarities in
the profiles of their SMs, they have been used
as taxonomic tool in plant systematic. However,
profiles of closely- related plants quite often differ
substantially or those of unrelated plant group
show strong similarities; this clearly shows that
SM patterns are not unambiguous systematic
markers but that convergent evolution and
selective gene expression are common themes.
Extraction of Secondary Metabolites from
Plant : Plant secondary metabolites are currently
the subject of much research interest, but their
extraction as part of phytochemical or biological
investigations presents specific challenges that
must be addressed throughout the solvent
extraction process. Successful extraction begins
with careful selection and preparation of plant
samples. During the extraction of plant material,
it is important to minimize interference from
compounds that may coextract with the target
compounds, and to avoid contamination of the
extract, as well as to prevent decomposition of
important metabolites or artifact formation as a
result of extraction conditions or solvent
impurities. Researchers from a variety of
scientific disciplines are confronted with the
challenge of extracting plant material with
solvents, often as a first step toward isolating and
identifying the speciûc compounds responsible
for biological activities associated with a plant
or a plant extract. The impetus for this research
arises largely because plants form the foundation
of traditional pharmacopeias, and because many
of our currently important pharmaceutical drugs
are obtained from plants. Further interest arises
from the growing awareness that many of the
secondary metabolites of organisms, including
plants, serve important biological and ecological
roles, mainly as chemical messengers and
defensive compounds. Investigators engaged in
the isolation of secondary metabolites from plants
soon discover the need for considerable
laboratory finesse in the apparently routine
‘‘sample preparation’’ steps that convert crude
plant material into an extract suitable for chemical
analysis, biological testing, or chromatographic
separation.
Major Secondary Metabolite Pathways : In
plants particularly three pathways are the source
of most secondary metabolites: The shikimate
pathway, the isoprenoid pathway and the
polyketide pathway. After the formation of the
major basic skeletons, further modifications
result in plant species specific compounds. The
shikimate pathway is the major source of
aromatic compounds. It is found in
microorganisms and plants, but not in mammals,
making it an interesting target for herbicides and
antibiotics, as these compounds are expected
not to have any effect on the mammalian system.
Glyphosate is a well known example. The
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enzymes channeling chorismate into the
aromatic amino acids pathways are chorismate
mutase and anthranilate synthase. Although, in
several plant species for both chorismate mutase
and anthranilate synthase more than one gene
has been cloned, only in case of chorismate
mutase a plastidial and a cytosolic enzyme have
been found. The phenylpropanoid pathway is one
of the most important metabolic pathways in
plants in terms of carbon flux. In a cell more than
20% of the total metabolism can go through this
pathway, the enzyme chorismate mutase is an
important regulatory point. The importance of this
pathway is due to the fact that it leads to among
others lignin, lignans, flavonoids, and
anthocyanins. Key to these products is the
enzyme phenylalanine ammonia lyase (PAL),
which converts phenylalanine into trans-cinnamic
acid by a non-oxidative deamination. This
enzyme can be found in all plants, in some plants
a single enzyme is found, whereas others may
have several iso-enzymes. The other important
pathway in plants is that of the terpenoids, also
known as isoprenoid pathway. Terpenoids include
more than one third of all known secondary
metabolites. Moreover, the C5-building block is
also incorporated in many other skeletons, e.g.
in anthraquinones, naphtoquinones,
cannabinoids, furanocoumarines, and terpenoid
indole alkaloids. In the “decoration” type of
reactions in various types of secondary
metabolites C5-units are attached to the basic
skeleton, e.g. hop bitter acids, flavonoids and
isoflavonoids.
Functions of Secondary Metabolites : Many
secondary compounds have signalling functions
influence the activities of other cells, control their
metabolic activities and co-ordinates the
development of the whole plant. Other
substances such as flower colours serve to
communicate with pollinators or protect the plants
from feeding by animals or infections by
producing specific phytoalexines after fungi
infections that inhibit the spreading of the fungi
mycelia within the plant (18). Plants use
secondary metabolites (such as volatile essential
oils and colored flavonoids or tetraterpenes) also
to attract insects for pollination or other animals
for seed dispersion, in this case secondary
metabolites serve as signal compounds.
Compounds belonging to the terpenoids,
alkaloids and flavonoids are currently used as
drugs or as dietary supplements to cure or
prevent various diseases (19) and in particular
some of these compounds seem to be efficient
in preventing and inhibiting various types of
cancer (20, 21). It has been estimated that 14-
28% of higher plant species are used medicinally
and that 74% of pharmacologically active plant
derived components were discovered after
following up on ethno-medicinal use of the plants
(22). Secondary metabolites are a metabolic
intermediates or product, found as a
differentiation product in restricted taxonomic
groups, not essential to growth and life of the
producing organism and biosynthetized from
one or more general metabolites by wider variety
of pathways than is available in general
metabolism.
Presence of volatile monoterpenes or
essential oils in the plants provides an important
defense strategy to the plants, particularly against
herbivorous insect pests and pathogenic fungi.
These volatile terpenoids also play a vital role in
plant-plant interactions and serve as attractants
for pollinators (23). They act as signalling
molecules and depict evolutionary relationship
with their functional roles. Soluble secondary
compounds such as cyanogenic glycosides
isoflavoids and alkaloids can also be toxic to
animals.
Biotechnology and Secondary Metabolites :
Since SM have evolved as compounds that are
important for the ûtness of the organisms
producing them, many of them interfere with the
pharmacological targets, which make them
interesting for several biotechnological
applications. Controlled clinical studies have
shown the efficacy of several, for example
extracts from Ginkgo biloba, Hypericum
perforatum, Piper methysticum, Chamomilla
recutita, Crataegus monogyna, Silibum
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marianum, Melissa ofûcinalis, Mentha piperita,
Valeriana ofûcinalis.
The use of stimulants (such as caffeine,
nicotine, ephedrine), fragrances (several
essential oils), ûavours (essential oils, capsaicin,
piperine, etc.), natural dyes, poisons (strychnine)
and hallucinogens (morphine, heroin, cocaine,
tetrahydro cannabinol) is based on SM. Since
many SM are insecticidal, fungicidal and
phytotoxic, they may be used in agriculture as
natural plant protectants. Before the advent of
synthetic pesticides about 60 years ago, plant-
derived insecticides (including nicotine, rotenone,
quassin, ryanodine, pyrethrins and azadirachtins)
were a common theme. Applications
unequivocally showed that these natural
insecticides worked. One ecological advantage
is that SM are readily degraded in plants and in
soil, is also their disadvantage and synthetic
pesticides are more resistant and persistent.
Moreover, modern pesticides are usually more
potent than biopesticides. On the other hand,
plants are easy to grow and biopesticides could
be a sustainable source of plant protectants for
farmers in countries that do not have access to
Western synthetic pesticides. Unfortunately,
legislation does not favour mixtures of
compounds to be used as pesticides; therefore,
the development of biorational pesticides has to
face many obstacles. Nevertheless, natural
compounds do provide an underexplored
alternative. As a consequence of these various
applications, a world market for plant extracts
and isolated SM exists, which exceeds 10 billion
US dollars annually. Therefore, it is a challenge
for biotechnologists to find ways to produce these
compounds in sufûcient quantity and quality.
The main and traditional way is to grow the
respective plants in the ûeld or in greenhouses
and to extract the products from them. For
several species, new varieties have been
selected with improved yields and quality. In this
context, cell and organ culture are important
techniques for in vitro propagation. In a few
instances, genetic engineering of secondary
metabolism has already had a direct inûuence
for example, when Atropa belladonna plants were
transformed with the gene that encodes the
enzymes converting L-hyoscyamine into L-
scopolamine, new plants were generated which
produced scopolamine as the major product.
More often, ûavonoid metabolism has been
altered genetically, producing plants with different
ûower colours. It is a challenge for future
research to isolate the genes of biosynthetic
pathways and to express them either in
transgenic plants or in microbes.
If successful, recombinant bacteria or
yeasts might be grown someday, which will
produce valuable plant SM. Combinatorial
biosynthesis might then be an open field. Using
genes encoding enzymes for the biosynthesis of
antibiotics, this strategy has already been
successful. It has also brought about renewed
interest in the regulation of SM synthesis and in
the location and means of sequestration of these
substances within the plant. In recent years,
attempts have been made to express the genes
of alkaloid biosynthesis in microorganisms.
Ultimately, it might be possible to produce
valuable alkaloids from recombinant bacteria or
yeast. If the corresponding SM (both from plant
or microbial origin) confers resistance to insects
or pathogens, genetic transformation of
susceptible crop plants could be another valuable
avenue for Exploitation. For more than two
decades, scientists around the world have tried
to produce valuable SM in cell or organ cultures.
Whereas undifferentiated cell cultures have often
failed to produce such a compound in reasonable
yields, differentiated organ cultures (e.g.
transformed root cultures) are often as active as
the intact plant .Cell- and tissue-speciûc gene
expression appears to control these processes.
In addresses the production of SM in vitro (Table
1).
It is possible that genetic engineering may
help to improve plant cell cultures as
biotechnological production systems in the future.
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Table1. Secondary Metabolites from Plant Cell, Tissue and Organs Cultures
Plant Name Active Ingredient Culture Type
Adhatoda vasica Vasine Shoot culture(24)
Agastache rugosa Rosmarinic acid Hairy root(25)
Ammi majus Umbelliferone Shootlet(26)
Triterpenoid Suspension(27)
Angelica gigas Deoursin Hairy root(28)
Arachis hypogaea Resveratol Hairy root(29)
Artemisia annua Artemisinin Callus(30)
Aspidosperma ramiflorum Ramiflorin Callus(31)
Azadirachta indica Azadirachtin Suspension(32)
Brucea javanica Cathin Suspension(33)
Bupleurum falcatum Saikosaponins Root(34)
Camellia chinensis Flavones Callus(35)
Capsicum annum Capsiacin Callus(36)
Cassia acutifolia Anthraquinones Suspension(37)
C. senna Anthraquinone Hairy root(38)
Catharanthus roseus Indole alkaloids Suspension(39)
Vincristine Suspension(40)
Catharathine Suspension(41)
Cayratia trifoliata Stilbenes Suspension(42)
Centella asiatica Asiaticoside Hairy root(43)
Callus(44)
Drosera rotundifolia 7-Methyljuglone Shoot culture(45)
Eleutherococcus senticosus Eleuthrosides Suspension(46)
Eriobotrya japonica Triterpenes Callus(46)
Fabiana imbricata Rutin Callus and Suspenson(47)
Fagopyrum esculentum Rutin Hairy root(48)
Fritillaria unibracteata Alkaloids Multiple shoot(49)
Gentiana macrophylla Glucoside Hairy root(50)
Gentianella austriaca Xanthone Multiple shoot(51)
Glycyrrhiza glabra Glycyrrhizin Hairy root(52)
Gymnema sylvestre Gymnemic acid Callus(53)
Hemidesmus indicus Lupeol, Rutin Shoot culture(54)
Hypericum perforatum Hypericin Multiple shoot(55)
Mentha arvensis Terpenoid Shoot(56)
Momordica charantia Flavonoid Callus(57)
Saurabh Pagare et al
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Conclusion
This review has dealt with a small
selection of plant secondary- metabolites and
their potential roles in defence mechanisms and
ecological adaptation, in addition to the topics
we have covered. there is an enormous range of
other compounds present in the plant kingdom,
with a very varied distribution. Plant secondary
metabolism produces products that aid in the
growth and development of plants but are not
required for the plant to survive. Secondary
metabolites have important ecological functions
in plants: They protect plants against being eaten
by herbivores and against being infected by
microbial pathogens. They serve as attractants
(odor, color, taste) for pollinators and seed-
dispersing animals. They function as agents of
plant-plant competition and plant-microbe
symbioses. The ability of plants to compete and
survive is therefore profoundly affected by the
ecological functions of their secondary
metabolites. Biotechnological approaches are
also involved in production of secondary
metabolites through genetic engineering process.
Plant tissue culture may also play a major role
for the same.
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