1. Plant Metabolites & Ergastic Cell
Contents

2. Primary Metabolites
 Primary metabolites
 chlorophyll
 AA’s
 Nucleotides
 Simple CHO’s
 Membrane lipids
 *** ARE FOUND
THROUGHOUT THE
PLANT KINGDOM
 Fx: Important roles
in growth and
development
 photosynthesis
 respiration
 solute transport
 translocation
 nutrient assimilation
 differentiation

3. Secondary Metabolites
 Definition:
 All organic compounds
 Have no direct function
in growth and
development
 Also called secondary
products or natural
products
 Differ from 1º metabolites
in that they have a
restricted distribution in
the plant kingdom
 Therefore: Only
particular secondary
metabolites are found
in only one specific
plant species or a
taxonomically related
group of species.

4. Secondary Metabolite Fx
 Initially thought to be functionless end
products of metabolism or metabolic waste
products
 Responsible for characteristics, odours,
pungencies & colours of plants. Others
give plants their medicinal, culinary or
poisonous values.
 They are synthesized to aid the producing
plant’s survival.

5. Secondary Metabolite Function
 Ecological functions in plants: protect
against herbivory
 Protect against infection by microbial
pathogens
 Attract pollinators & seed distributing
animals
 Act as agents for plant-plant competition

6. Evolution of 2º Metabolites
 2º Metabolites evolved through mutations in the basic
metabolic pathways
  appearance of new compounds
 happened to be toxic or a deterrent to herbivores and pathogens
• As long as they were not toxic to the plant itself and were produced
at a low metabolic cost
 They gave the plants containing them greater
reproduction fitness than undefended plants (plant-
plant competition)
 Undefended plants therefore left more descendants
while the protected plants left less
 And passed their defensive traits on to the next generation

7.  The defence compounds (secondary
metabolites) that increase reproductive
fitness of plants by warding off fungi,
bacteria and herbivores, also make them
undesirable as food by humans.
 Many NB crop plants have been artificially
selected for producing relatively low levels
of these compounds, which make them
more susceptible to insects and disease
 (e.g. of Wheat)

8. 3 MAIN GROUPS OF 2º
METABOLITES
 TERPENES
 PHENOLS
 N2-CONTAINING COMPOUNDS

9. Terpenes
 Terpenes are lipids
 synthesized from acetyl CoA or from the
basic intermediates of glycosides

10. Phenolic compounds
 Phenolic compounds are aromatic
substances
 Formed via the Shikimic acid Pathway or the
Malonic acid pathway

11. Nitrogen-containing compounds
 e.g. alkaloids
 synthesized from AA’s

12. Active Plant Constituents

13. Carbohydrates
 Sugars (glucose,
xylose)
 Starches (energy
stores)
 Cellulose (structural
support)
 Gums & mucilage

14. Gums & Mucilages
 Very complex CHO’s
 Found in excellent
vulnerary, demulcent
& emollient herbs.
 E.g. Marshmallow &
Plantain

15. Gums & Mucilage Fx
 Relax Gut lining
 Relax Respiratory
System
 Reduce irritation and
inflammation (GIT,
Respiratory, US)
 MO: soak up large
amounts of water
  sticky jelly: dry
irritated skin,
inflamed/painful tissues
 Some stimulate
immune system: e.g.
Acemannan (Aloe
vera)

16. Plant Alcohols
 Occurs in plants in
various forms
 Constituent of volatile
oils & sterols
 Attar of Rose
 Menthol in peppermint
 Waxes (beeswax)
 Cutins

17. Phenols
 Phenol = basic building
block for many plant
constituents
 Simple/complex in nature
 Fx:
 anti-inflammatory
 Anti-septic
 E.g. Salicylic acid
(Willow)
 Eugenol (Clove)
 Thymol (Thyme)

18. Volatile Oil Function
 Anti-spetic
(Garlic/Thyme oil)
 Stimulate tissue
 irritation e.g.
Mustard
 numbing e.g.
Camphor oil).
 Aid digestion
 CNS action
 Insect repellent
 Anti-inflammatory
 Anti-allergenic

19. Proanthrocyanins
 Closely related to
tannins & flavonoids
 Phenols
 Fx: powerful anti-
oxidants
 Protect circulation
from damage:
especially circulation
of the heart, hands,
feet & eyes.
 E.g. Crataegus spp.

20. Tannins
 Fx – give herbs their
astringent & heamostypic
action
 Act on proteins and form
a protective layer on the
skin & mucous
membranes
 Bind the tissues of the gut
 Reduce diarrhoea &
internal bleeding
 Externally: Rxing burns,
sealing wounds & reducing
inflammation.
 Heal infections of the eye,
mouth, vagina, cervix &
rectum (mucous membrane
tissues)  Tannins - phenols

21. Coumarins
 (smell of cut grass)
 Limited effects on the
body
 Di-coumarol, (metabolite)
 powerful anti-clotting
agent.
 Functions:
 Allopathic: Basis for
warfarin (thrombosis in
small doses): Horse
Chestnut
 (Rat poison in large doses)
 Visnaga – powerful smooth
muscle relaxant

22. Anthraquinones
 Plants containing
anthraquinones 
effective purgatives
 (& good natural dyes)
 Senna & Aloe
 Also make stool more
liquid (Constipation)
 Fx: gently stimulate
colon 8-12 hrs after
ingestion (stimulate
peristalsis)
 Can only Fx when natural
bile is present.
 Tend to cause colonic
pain (over-stimulate colon
wall)

23. Glycosides
 Flavonoids
 Saponins
 Phenolic glycosides
 Cardiac Glycosides
 Cyanogenic Glycosides

24. Flavonoids
 One of the most common
group of plant
constituents
 Polyphenols
 Wide range of actions
 Anti-spasmoidic
 Anti-inflammatory
 Anti-oxidant
 Diuretic
 Circulatory Stimulants
 Cardiac stimulants
 Anti-viral
 hepatic

25. Saponins
 Pharmaceutical Chemists
 synthesis of cortisone
(anti-inflammatory) & sex
hormones
 Saponins in herbs do not
act in the same way 
body can use them as
building blocks to form
appropriate chemicals.
Fx:
 anti-inflammatory
 Expectorant
 Aid nutrient absorption

26. Cardiac Glycosides
 Discovered from
Foxglove (1785) 
recognised to support a
failing heart
 Many flowering plants
contain cardiac
glycosides
 Fx: increase heart
efficiency
 Steady tachycardia
 NO CARDIAC STRAIN
 Strong diuretic

27. Cyanogenic Glycosides
 Based on cyanide
(toxic)
 Small doses
 Sedative
 Relaxant effect on
heart & muscle
 Wild cherry bark:
suppress & soothe
dry, irritating coughs.
 Fruit kernels (apricot)

28. Bitter Principles
 Group of chemicals with
an exceedingly bitter
taste
 Wide diversity of structure
 Most belong to the
iridoids, some to terpenes
 Fx: stimulate digestive
juices & appetite
 Aid the liver
 Anti-biotic
 Anti-fungal
 Anti-tumour
 Play specific roles
depending on herb &
chemical combination e.g.
Valerian & Devil’s claw

29. Alkaloids
 The most potent group of
plant constituents
 Effect: body & mind
 Some: effect on lungs,
liver, nerves, GIT
 Fx in plant: source of
excessive N2. (makes
them pharmacologically
active).
 Divided into 13 groups
based on their chemical
structure (no general
effects)
 E.g. Atropine (Atropa
belladonna)  reduce
spasms, relieve pain &
dry up bodily secretions

30. Glucosilinates
 Found exclusively in the
Brassica Family (Mustard
& Cabbage)
 Instant blistering &
inflammatory effect on the
skin
 Applied to painful areas
to increase blood flow
 Helps remove excessive
waste products
 Eating: produce a strong
pungent taste.

31. Vitamins
 Found in many
medicinal plants
 Lemon peel: Vitamin
C
 Carrot: Vitamin A
 Brewers Yeast: B-
vitamins
 Nasturium/watercress:
Vitamin E

32. Minerals
 Plants draw minerals
from the soil and convert
them into a form which is
easily absorbed & used
by the body.
 Kelp: I2
 Dandelion: K
 Horsetail: Silica
 Nettle: Fe & Ca
 Brewers Yeast:
Chromium

33. CALCIUM OXALATE
CRYSTALS

34. Calcium Oxalate
 Numerous crystals occur in plants
 Ca-oxalate is one of the most common
 Like trichomes & stomata, it also has
diagnostic value
 X polymorphs are characteristic in x plant
spp.

35. Crystal Systems
 In plants  2 crystal systems exist
 All crystal polymorphs belong to one of
these systems
 Systems
 Tetragonal System
 Monoclinic System
 Systems differ
 in the amount of water they attain
 OD

36. Tetragonal Crystal System
 Composition:
CaC2O4.3H20
 Arises from
supersaturation of the
cell sap with calcium
oxalate
 Includes
 Prisms
 Cluster crystals
(rosette aggregates)
 microsphenoids

37. Monoclinic Crystal System
 Chemical composition: CaC2O4.H20
 Form in the presence of excess oxalic acid
 Crystal forms include
 Some prisms
 Needle-like crystals (raphides)
 Sphaero-crystals

38. NB!!!
 When using Calcium
oxalate crystal types
as a diagnostic tool:
 Crystal type
 Size
 Distribution
Should all be noted.

39. Crystal Function
 Uncertain
 More abundant in plants growing in arid
regions.
 Ca: Causes epithelial cells to swell
 Deter herbivory?

40. Crystal Forms
 Prisms
 Cluster Crystals
 Microsphenoids
 Raphides
 Sheaero-crystals

41. Prisms – Elletaria cardamomum
 Found in
Cardamom
• Small single prisms
• Starch masses in
parenchyma

42. Prisms – Hyosciamus niger
 Black henbane
• Single prisms
 Some have a
crystalline outgrowth
(plug)
• Twin prisms
 In crystal layer of
spongy mesophyll
cells (directly below
palisade tissues)

43. Prisms – Cassia senna
Senna
* Single prisms
* Occurs in
parenchyma cells
* Surrounds bundles of
pericyclic fibres
* Forms a crystal
sheath

44. Prisms – Glycyrrhiza glabra
Found in Liquorice
* Single prisms
* Occurs in parechyma
tissue
* Surrounds xylem &
phloem
* Forms an incomplete
crystal sheath

45. Prisms – Rhamnus purshianus
 Cascara senega
 Crystal sheaths
 Similar to liquorice
 Occurs with the
phloem fibres
 Complete crystal
sheaths

46. Microsphenoids
 Atropa belladonna
 Aggregates occur in a
crystal layer
 Below palisade tissues
 When a single cell
contains an aggregate
of microsphenoids
 idioblast

47. Raphides
 Occur
 Singly
• E.g. Ipecavanha
 In bundles
• E.g Squill

48. Diagnostic Value of Calcium
Oxalate Crystals
 Absence of crystals
 Different form
 Different size
 all used to identify adulterants or allied
species from medicinal herbs.

49. Diagnostic Value of Calcium
Oxalates
 E.g.
Digitalis purpurea:
(used medicinally) no
calcium oxalates
D. thapsi: (not used
medicinally) - small
prisms

50. Diagnostic Value of Calcium
Oxalate Crystals
 E.g.
Atropa belladonna:
Leaves have micro-
sphenoids
Phytolacca leaves:
have raphides

51. Diagnostic Value of Calcium
Oxalate Crystals
 3 Solanaceous Herbs
 Atropa belladonna
• Microspenoids
 Datura stramonium
• Cluster crystals
 Hyoscyamus nigra
• Prisms

52. LESSON TAKE-AWAY
 Definition & types/effects of adulteration
 Difference between 1º & 2º metabolites.
 E.g’s & Functions of metabolites
 Types of Ca-O crystals (E.g’s & Dx value)

53. End of Lesson
 Thank You!