8. Primary and secondary plant metabolites I.

Universal and specific plant metabolism

1

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

2

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

3

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

-

5

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

6

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

8

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)

9

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

10

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)

11

Carbohydrates

12

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

14

Non-digestable oligosaccharides

• Raffinose, stachyose and verbascose are non-

digestible saccharides

• Mainly in fabaceous plantsas stored nutrients

• Can cause bloating

15

• Starch

• Cellulose

• Inulin

SACCHARIDES = CARBOHYDRATES

polysaccharides

homopolysaccharides

heteropolysaccharides

• Mucilage

• Gums

• Pectins

structural and reserve polysaccharides

16

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

18

Phenoloids

19

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

20

POLYKETIDSnitrogen

metabolism PHENOLOIDSshikimic acid pathway

cinnamic acid

derivates flavonoids

phenolic

quinones

phenolic

glycosides

tanninsaromatic

amino acids

Illicium anisatum – Japanese star anise

lignoids coumarines

21

• 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

23

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

24

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

25

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)

27

myrtillin - blueberry genistein – soybean

quercetin - lovageapigenin - chamomille naringin - grapefruit

catechin - tea

aromadedrin– siberian pine

28

• 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

29

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

30

• 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

31

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

32

Fatty acids and polyketides

33

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

34

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

35

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

36

Terpenoids

37

mevalonic acid

(MEV) pathway methyl-erythritol-

phosphate (MEP)

pathway

geranyl diphosphate (GDP)

farnesyl diphosphate (FDP)

geranylgeranyl diphosphate (GGDP)

Terpenoid

synthesis

38

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

39

• 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)

40

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

41

• 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

43

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)

44

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)

45

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

47

Saponins

Not a single biosynthetic group!

Amphipathic glycosides – emulsifying effect

Sapo (in Latin): soap – produce foam in the rumen (see

seminar 3)

48

• 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

50

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

52

• 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