8. primary and secondary plant metabolites i. · protein and nucleic acid synthesis (primary...
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8. Primary and secondary plant metabolites I.
Universal and specific plant metabolism
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Histology
Cytology
Morphology
Taxonomy
Plant physiology
PLANT METABOLITE ANIMAL
Primary plant
metabolites
Secondary plant
metabolites
Poisonous
compounds
Medicinal
compounds
Antinutritive
compounds
Forage
Plants with a
veterinarian
importance
The subject of veterinary botany
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Synthesized directly
from inorganic
compounds (simple
sugars, amino acids)
General plant metabolites
(CH, proteins, fatty acids)
Essential compounds
for life processes and
growth
permanent transition between primary and secondary
metabolites
Non-general compounds, with
small proportions in the cells
Derived from primary metabolites
Non-essential elements for life
processes
Do not take apart of primary
metabolism and energy flow
Their major role is in the
interspecific interactions
Produces in specific cells, stored in
vacuoles and intercellular cavities
Primary metabolites Secondary metabolites
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About plant metabolites in generalDue to the different metabolic pathways universal and
specific metabolites
Universal plant metabolism: photosynthesis, respiration,
protein and nucleic acid synthesis (primary metabolites)
Specific plant metabolism: taxonspecific series of metabolic
processes with specific enzymes (secondary metabolites)
The occurence of secondary metabolites is taxonspecific
Major groups of secondary metabolites (based on their
biosythesis)
1. Saccharides
2. Phenoloids
3. Polyketides
4. Terpenoids
5. Azotoids 4
System of plant metabolites due tobiosynthetic pathways
SACCHARIDES PHENOLOIDS POLYKETIDES TERPENOIDS AZOTOIDS
CO2 SO42- NO3
-
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Primary and secondary metabolicpathways in plants
CO2 SO42- NO3
-
pyruvate acetyl-CoA
pentose phosphate pathway
citric acid cycle
malonyl-CoA
shikimic acid
SACCHARIDES PHENOLOIDS POLYKETIDES TERPENOIDS AZOTOIDS
Calvin cycle
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amino acids,
nucleic acids
Photo-
syn-
thesis
Termi-
nal oxi-
dation
Glycolysis
Calvin
cycle
sugars
pyruvate
Citric
acid
cycle sesquiterpenoids
Plant primary and secondary metabolism
shikimic acidcinnamic
acid
gallic
acid
acetyl-CoA
universal
fatty acidsmalonyl-CoA
isoprene
diterpenoids
monoterpenoids
monosaccharides
(sugars) polysaccharides
oligosaccharides
SACCHARIDES
lignoids
flavonoids
coumarins
quinones
phenolic glycosides
tannins
PHENOLOIDS
cyanogenic glycosides
alkaloids
glucosinolates
AZOTOIDS
specific polyketides
specific fatty acids
POLYKETIDES
tetraterpenoids
triterpenoids
polyterpenoids
steroids saponins
TERPENOIDSFATTY ACID metabolism
NITROGEN
metabolism
CARBOHY-
DRATE
metabolism
CO2
System of secondary plant metabolites
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The role of secondary metabolites in plants
Regulation of growth – plant hormones:
gibberellic acid
Allelopathic compounds – regulate the
growth of other species (growth-stunting effect)
• juglone (Juglans regia – walnut)
• artemisinin (Artemisia annua – sweet
wormwood)
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Pollinator attractants – to support
fertilization or to catch insects
(carnivorous plants)
Insecticides – pyretroids
(Chrysanthemum cinerariaefolium –
pyrethrum) against lice and fleas
Insect repellents
• thymol (Thymus spp. – thyme
species) against snails
• linalool (Lavandula spp. –
lavander species) against moths
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Defense mechanism againstherbivores
• capsaicin (Capsicum spp. –
pepper species)
• solanine (Solanum spp. –
nightshade species)
Antimicrobial and antifungaleffect (inhibition of growth and
reproduction)
• resveratrol in grapes,
raspberries
•carvacrol (Thymus spp. –
thyme species)
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Carbohydrates
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Sweet tasteWater soluble
Sugar alcoholsAldehyde aldose
Ketone ketose
Trioses – C3
Tetroses – C4Pentoses – C5 constituents of DNA, RNA
Hexoses – C6 dietery energy source
SACCHARIDES = CARBOHYDRATES
general formula: (CH2O)n
monosaccharides
oligosaccharides
polysaccharides
Universal (glucose) and specific (digitoxose) sugars in glycosides13
SACCHARIDES = CARBOHYDRATES
oligosaccharides
disaccharides oligosaccharides consists
of 3-9 monomers
Two joined monosaccharides
Dietery energy source
• Consists of different
monosaccharide units
• Well transportablereserve carbohydrates
• Components of
hemicelluslose
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Non-digestable oligosaccharides
• Raffinose, stachyose and verbascose are non-
digestible saccharides
• Mainly in fabaceous plantsas stored nutrients
• Can cause bloating
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• Starch
• Cellulose
• Inulin
SACCHARIDES = CARBOHYDRATES
polysaccharides
homopolysaccharides
heteropolysaccharides
• Mucilage
• Gums
• Pectins
structural and reserve polysaccharides
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Non-starch polysaccharides (NSP)Major structural elements in the cell wall (cellulose,
hemicellulose, pectin)
Beta-glucans and arabinoxylans – mainly in cereals and pulse
crops
Water absorption sticky faeces syndrome
β-glucan Arabino-
xylan
total
hulled rice 0 0 0
millet 1 28 29
maize 1 43 44
wheat 5 61 66
triticale 7 70 77
rye 12 89 101
barley 33 76 109
oat 42
NSP compounds of cereals (g/kg dry matter)17
Glycosides
Not a single biosynthetic group!
When a sugar is bound to another functional group via a glycosidic bond glycosides
Groups according to the aglycon part:
• Cyanogenic glycosides, glucosinoates azotoids
• Cardiac glycosides, saponins terpenoids
• Rutin (rutoside) phenoloids
Carbohydrate, nitrogen and fatty acid metabolic pathways are
linked in their biosynthesis
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Phenoloids
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Consist of one or more aromatic rings and a –OH (hydroxyl) group
Phenoloids biosythesized mainly from shikimic acid orcinnamic acid
Phenolic compounds are general in many plant taxa
About phenoloids in general
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POLYKETIDSnitrogen
metabolism PHENOLOIDSshikimic acid pathway
cinnamic acid
derivates flavonoids
phenolic
quinones
phenolic
glycosides
tanninsaromatic
amino acids
Illicium anisatum – Japanese star anise
lignoids coumarines
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• Widely distributed in nature
• The aglycone part is a phenolic compoundwith hydroxyl, aldehyde or carboxyl groups
• Glycosides of salicylic acid – anti-inflammatory,
anti-fungal effect
• Simple hydroquinon glycosides – arbutin:
urinary antiseptic effectSalix alba – white willow
PHENOLOIDS
cinnamic acid
derivates
phenolic
glycosides
22Arctostaphylos uva-ursi -
bearberry
Natural occurence in species of
Rosaceae and Ericaceae families
Naphthoquinones
phenolic
quinones
Juglans regia - walnut Lawsonia inermis - henna
PHENOLOIDS
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Staining compounds, allelopathic effects
Some quinones are produced via polyketide pathway see later
Derived from phenylpropaneunits (cinnamic alcohol)
Lignins: polymer molecules
of the secondary cell wall
Degraded only by certain
microbes and fungi
Lignans: dimer molecules
Antioxydant and estrogen-like
effect
Linum usitatissimum - flax
Silybum marianum –
St. Mary’s thistle
cinnamic acid
derivates
lignoidsPHENOLOIDS
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cinnamic alcohol
Derived from phenylpropane units(cinnamic acid)
Occurs only members of a fewfamilies (e.g. Apiaceae, Rutaceae,
Asteraceae and Fabaceae)
Hydroxy coumarins and coumarindimers (dicoumarol)
anticoagulant effect
Furanocoumarine
(photosensitization, highly toxic
for fish)
Melilotus officinalis –
yellow sweet clover
Ruta graveolens
- rue
Galium odoratum – sweet woodruff
PHENOLOIDS
cinnamic acid
derivates
coumarines
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cinnamic acid
Flavonoids
• Universal plant pigments
• ~4000 different pH-sensitivemolecules
• Subdivided into groupsaccording to the position of phenyl ring isoflavones, neoflavonoids, trueflavonoids
• According to the degree of unsaturation and oxidationthe true flavonoids can divideinto several groups
Phenoloidpathway
Polyketide pathway
chromane ring
phenyl ring
true flavonoid isoflavonoidneoflavonoid
sugar moety26
Major groups of flavonoids
true flavonoids
isoflavones
neoflavonoids
chalcones (with an open chromane ring)
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myrtillin - blueberry genistein – soybean
quercetin - lovageapigenin - chamomille naringin - grapefruit
catechin - tea
aromadedrin– siberian pine
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• Activation of cytochrome-P450 enzymes
• Antioxidants effect – neutralize free radicals decreasing
toxic effects
• Immonstimulant effect – exact mechanism is not known
• Membrane interaction: some compounds can inhibit
histamine release
• Reduce risk of atherosclerosis
• Antiinflammatory agents
• Used in prevention of cardiovascular deseases
• Isoflavonoids are phytoestrogenes with insecticide activity
• Also in plants used as antidotes of snake venom
Biological effects of (iso)flavonoids
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Biflavonoids
Some biflavanoids are used as a treatment for memory disorders
improve cognitive functions and decrease side effects (anxiety,
dizziness, tinnitus, memory loss)
Ginkgo biloba - gingko
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• Tannins are widely distributed in
the plant kingdom
• Dicot families rich in tannins:
Rosaceae, Fabaceae,
Geraniaceae
• Tannin containing plants: Quercus
spp., Betula spp., Pinus spp.
• Hydrolyzable tannins (Hts): a
glucose with phenolic groups
(gallic acid)
• Condensed tannins(proanthocyanidins (Pas)):
oligomers or polymers of flavonoid
units (e.g. catechin)
tanninsPHENOLOIDS
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Hts: precipitate proteins water insoluble complexes
Antinutritive and poisonous effects, treatment of diarrhea
( see detailed mechanism and symptoms in seminar 3, 6)
Pas: medicinal effects
Camelia sinensis – tea plant
Quercus cerris –
turkey oak
Biological effects of tannins
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Fatty acids and polyketides
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Acetil CoA
Malonil CoA
tetracycline antibiotics
fatty acidmetabolism
poly-β-keto acidsspecific polyketides
saturated and
unsaturated fatty
acids
polyyne
Polyketide synthesis
Chainelongationwith a C2 keto
group
universal
polyketides
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Chaeroplyllum temulum –
rough chervil Oenanthe aquatica – water dropwort
Saturated and
unsaturated fatty
acids
Fatty acid metabolism
PolyynesAlternating single and
triple bonds
In fungi and plants
(Apiaceae)
Herbal toxins affect theCNS
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Polyketide chains are highly unstable ring
closing reactions aromatic rings
1. Phloroglucinol derivates (e.g. humulone) –
various effects
2. Anthraquinones (e.g. emodin) - laxative
3. Naphthodianthrones (e.g. hypericin) -
photosensitization
Humulus
lupulus -
hop
Specific polyketides
Cassia senna - senna
Hypericum
perforatum –
St. John’s wort
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Terpenoids
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mevalonic acid
(MEV) pathway methyl-erythritol-
phosphate (MEP)
pathway
geranyl diphosphate (GDP)
farnesyl diphosphate (FDP)
geranylgeranyl diphosphate (GGDP)
Terpenoid
synthesis
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Monoterpenes (C10)
General occurence in
plants
Volatile compounds inoils
Acyclic, monocylic(limonene in citrus fruits)
and bicyclic (pinene in
tansy) molecules and their
derivates
Monoterpenes oftenproduce an odour
They are rarely
accumulated in tissues
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• Allelopathic effect
• Insect repellent effect (menthol, myrcene, camphor)
• Pollinator attractants (pinene, eucalyptol)
• Antimicrobial, antifungal effect (carvacol)
• Toxic effects (pinene, thujone)
Effects and functions of
monoterpenes (C10)
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Non-volatile monoterpene derivates
Iridoids
Protective chemicals(microbes, fungi, herbivores
in a glycosidic form)
The flavour of iridoids is
distinctly bitter
Medicinal effects: sedative,
anti-inflammatory,
antibacterial
Pyrethrines
Insecticidal activity by
targeting the nervous system used against parasites
Chrysanthemum cinerariaefolium –
Dalmatian chrysanthemum
Valeriana officinalis - valerian
Plantago lanceolata –
ribwort plantain
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• Natural occurence mainly in Asteraceaefamily
• Acylic or cyclic compounds
• Can be present in oils, but less volatile
than monoterpenes
• Various effect: apetizing effect,
antispasmodic, painkillers but allergic
reaction and photosensitization is also
possible
Matricaria chamomilla –
German chamomilleSesquiterpenes (C15)
Humulus lupulus
- hop42
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Volatile (essential) oils
Not a single metabolite group!
A mixture of metabolites:
• mono and sesquiterpenes and their
derivatives
• phenypropanoids
• phenoloids
• other volatile compounds
Adsorbed from skin or the mucous
membranes of mouth or lungs
Can excreted with breath, digestion or
with urine
Effects (at the site of excretion): antiseptic, antispasmodic,
sedative, irrittive, toxic
• More than 2000 different molecules
• Apolar or semi-polar non-volatile compounds
• Plant hormones: regulate growth and
developement – gibberellic acid
• Toxic effets: irraritation, tumor promoters(phorbol)
• Medicinal effects: spasmolytic, cytostatic
compounds, antibacterial, antifungal and anti-
inflammatory activity, cardioactive effects
• Poisonous derivates with nitrogenheterocycles pseudoalkaloids (taxines,
aconitine) cardiac and CNS effect
Diterpenes (C20)
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Taxus baccata –
yew
Aconitum napellus -
monkshoodEuphorbia cyparissias
– cypress spurge
Stevia
rebaudiana -
candyleaf
Ginkgo biloba -
ginkgo
Salvia sclarea
– clary sageabietanes
tiglianes
cauranes
taxanes
Groups of
diterpenes (C20)
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Bitter substancesNot a single biosynthetic group!
Stimulate taste receptors increased
production of saliva and gastric juices
The bitterness value is the reciprocal of the dilution of a bitter
compound. It is determined by comparison with quinine
hydrochloride (bitterness value 200 000)
Bitter substances are mainly terpenoidgroups:
• monoterpene derivates (iridoids): oleuropein
• sesquiterpene lactons: artemisinin,
• diterpenoids: ginkgolide
Buxus
sempervirens –
boxwood
Artemisia absinthium –
wormwood46
Triterpenes (C30)
phytosterols
(C27-29)
triterpenoid
saponins (C30)
steroidal
glycoalkaloids
cardiac
glycosides
(C23, C24)
steroidal
saponins (C27)
squalene
cholesterol
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Saponins
Not a single biosynthetic group!
Amphipathic glycosides – emulsifying effect
Sapo (in Latin): soap – produce foam in the rumen (see
seminar 3)
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• Synthesized from squalene, with five rings bounds with
sugar saponin effect
• Poisonous/antinutritiveeffects (see previously) – fishes
are susceptible
• Medicinal effects: antibacterial,
antifungal and anti-inflammatory
activity, immunostimulant
githagosid
glycyrrhizin
aescin
Medicago sativa –
lucern
Agrostemma
githago –
corn cockle
Aesculus
hippocastanum –
horse chesnut
Glycyrrhiza glabra
– liquorice49
triterpenoid
saponins (C30)
• Generally four ringed molecules
• Dietery supplies
• Decrease cholesterol level
• Poisonous effects cucurbitacins
• Ginsenosides: steroid glycosides and triterpene
saponins exclusively in Panax spp. (ginseng)
• Triterpene saponins have a tetracyclic aglycon
• Adaptogen (stabilization of physiological
processes), radioprotective (reduce the effects of
radiation), anti-tumor activity
Panax ginseng –
ginseng
protopanaxadiol
phytosterols
(C27-29)Cucurbita pepo
– marrow
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triterpenoid
saponins (C30)
• The glycon parts are mostly
oligosaccharides, the aglyconpart are spirostanol or
furostanol
• Cytotoxic and antifungal activity
• Diosgenin – precursor of
synthetic steroidal and anti-cancer
drugs
steroidal
saponins (C27)
Dioscorea villosa
– wild yam
Trigonella foenum-graecum
– fenugreek51
• Aglycons bounds with specificsugar moieties glycosidic form
with saponin effect
• Inhibition of the membrane boundNa+/K+ pump irregular and slow
heart beat ( see seminar 4.)
cardiac
glycosides
(C23, C24)
Helleborus purpurascens
– purple hellebore
Bufo bufo –
common toad
Convallaria majalis
– lily-of-the-valley
Digitalis purpurea –
purple foxglove
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• Biosynthesized from cholesterolwith a nitrogen in heterocycle
pseudoalkaloids
• Bitter flavour
• Toxic effects see seminar 5.
steroidal
glycoalkaloids
Solanum nigrum –
black nightshade53
• Derived from two GGPP molecules
• Carotenoid plant pigments – UV
protection
• In chromoplastids of roots, flowers
and fruits
Tetraterpenes (C40)
54
• Acyclic polymers containing a large number of isoprene
subunits
• Natural rubber in the latex of rubber tree
Polyterpenes (C40)
Hevea brasiliensis – Pará rubber tree55