secondary metabolites

2. According to WHO survey nearly 70% -
80% of total world population depends upon
herbal drugs.
The production of specialty chemicals by
plants is a multibillion industry.

3. WHAT ARE SECONDARY
METABOLITES?
They are the phytochemicals that do not
participate in plant metabolism.
They are not directly needed by plants as they
don’t perform any physiological functions.
They may include pharmaceuticals, flavors,
fragrances, cosmetics, food additives, feed stocks,
antimicrobials.

4. WHY IN VITRO?
Compounds can be produced under controlled
conditions as per market demands.
Independent of environmental factors.
Quality will be consistent as the products are
formed by a specific cell line.
Easy recovery strategies can be applied
Novel products can be produced via mutant cell
lines.
Biotransformation can be done.

5. MAJOR ADVANTAGES
Compounds can be produced under controlled conditions as per
market demand.
Culture system is independent of envt. Factors.
Cell growth can be controlled to facilitate improved product
formation.
Quality of product will be consistent as it produced by a specific
cell lines.
Recovery of product will be easy.
Mutant cell lines can be developed for the production of novel
compounds of commercial importance which are not normally
found in plant.
Production time is less and labor cost are minimal.
Biotransformation

6. MAJOR LIMITATIONS:
Lower quantity in comparison to field plants.
Lower quantity in comparison to permanent tissue.
Cultured cells are genetically unstable, so,
susceptible to mutation.
Aging of the culture adversely affect the
production level.
Vigorous stirring may damage the cells.

7. WHY DO PLANTS PRODUCE 2°-
METABOLITES?
For protecting themselves from infections by
producing some antimicrobial compounds called
phytoalexins.
It is believed that production of 2°-metabolites is
linked to the induction of morphological
differentiation.
It is often seen that some of differentiated tissues get
specialized to produce specific 2°-metabolites, and in
comparison to in vitro cultures, which are the masses of
undifferentiated cells, produces higher level of 2°-
metabolites.

8. APPLICATIONS OF 2°-
METABOLITES:
Chemically they may be alkaloids, terpenoids,
glycosides etc.
Pharmaceuticals, flavors, perfumes,
agrochemicals, insecticides and raw materials
for industries.
Shikonine-A dye from Lithospermum
erythrorhizon.
Production of 2°-metabolites is a multibillion
industry.
One kg of vincristine and vinblastine cost

9. Name of the 2°-Metabolites Pharmaceutical Uses
Codenine Analgesics
Quinine Anti-malarial
Atropine Muscle relaxants
Digoxin Treatment of cardiovascular
disorders
Reserpine Hypotensives
Jasmine Perfumes
Pyrithrins Insecticides
Stevioside Food sweeteners
Vincristine Anticancer agents

10. STRATEGIES FOR PRODUCTION
OF 2°-METABOLITES IN VITRO

11. Selection of cell lines for high yield of
secondary metabolites.
Large scale cultivation of plant cells
Medium composition and effect of nutrients
Elicitor induced production of sec. met.
Effect of envt. Factors.
Biotransformation using plant cell culture.
Secondary metabolites release and analysis.

12. I. SELECTION OF CELL LINES FOR HIGH
YIELD:
Separation of producer cells from the non-
producer ones.
Euphorbia mili – anthocyanin- Yamada and
Fujita (1973)
Shikonin-

14. Not all cell types produce the
desired metabolite
Within a specific cultivar of Catharanthus
roseus, 62% of the clones produced the
desired metabolite
whereas in another only 0.3% produced the
metabolite

15. Culture conditions must be
optimized
e.g. concentrations of sugar, hormones, and
vitamins
light
temperature

17. Metabolite production is frequently
higher in cell cultures
Berberine production from Coptis japonica
is about 5% of dry weight after 5 years of
root growth, which equals 0.17 mg/g per
week.
Whereas in selected cell lines it can be
13.2% of the dry weight in cell culture after
3 weeks, which is about 44 mg/g/week or
about 250 times higher

19. Many secondary metabolites are
produced in roots
Scientists have developed a form of root culture
using Agrobacterium rhizogenes, the cause of
hairy root disease. (Show Fig 14.3)
Cells transformed with some of the bacteria’s
DNA, causes the cells to be more sensitive to
the hormones they produce. The cells form into
roots. These roots grow very fast and produce
the secondary metabolites that ordinary roots
produce.

20. Root cultures are often better
than cell cultures
Roots often secrete the metabolites into the
surrounding medium, making it easy for
collection.
Charcoal can be added to the medium, the
metabolites are absorbed by the charcoal,
and this stimulates even higher production
of the metabolite.

21. For optimal production of secondary
metabolites a two medium approach is
desirable.
First medium: reqd for good growth of cells.
Second medium: refer to as production
medium promotes secondary metabolites
production.

22. Effect of precursors
Addition of precursors to the medium
enhances product formation.
Eg: ornithine, phenylalanine, tyrosine and
sodium phenylpyruvate, precursors
typtamine and secologanin increase
ajmalicine production in C.roseus culture.

23. Production- very low, demand- not met…
Effort : for product formation at molecular
level, and exploit the ways for increased
production.
Elicitors are the compounds of biological
origin which stimulate the production of
secondary metabolites, and the phenomenon
is called ELICITATION.

24. ELICITORS
ENDOGENOUS EXOGENOUS
ABIOTICBIOTIC
All elicitors
of biological
origin
Physical agent:
heat, cold, UV,
osmotic pressure
Chemical agent:
antibiotics,
fungicide, etc..
Produced by
microbes. Eg:
chitin, chitosan,
glucans.
Within plant cell:
pectin, pectic acid,
cellulose, etc
METHODOLOGY FOR ELICITATION
a) Selection of microorganisms
b) Co-culture

25. Effect of light
Effect of incubation temp
Effect of pH
Aeration of culture

26. Conversion of one chemical into another by
using biological system as biocatalyst is
regarded as biotransformation or
bioconversion.
Conversion of some less imp substances to
valuable medicinal or commercially
important products.
Bioconversion may involve many reaction
eg: hydroxylation, reduction, glycosylation.

27. Good eg is : large scale production of cardiovascular
drug digoxin from digitoxin by Digitalis lanata.
Cell culture Digitalis purpurea or Stevia rebaudiana
can convert steviol into steviobiocide and steviocide
which are 100 times sweeter than cane sugar,

28. For secondary metabolites stored in vacuoles of
cells, two membranes have to be disrupted.
Permeabilizing agents such as DMSO can be
used for the release of products.
Separation and purification is costly, so two
approach are made:
a) Production of sec. met. Should be high as
possible
b) Formation of side product which interfere must
be minimal.

30. Kinds of Secondary Metabolites
alkaloids
phenolics (including polyphenols and
tannins)
terpenoids

32. Precursors can be fed to either cell culture or
roots to produce the metabolite in question.
In addition, cells can be genetically
engineered to over-produce the metabolite,
but this may be more difficult with pathways
that have many enzymes.

33. Some secondary metabolites
produced in cell and root
culture
L-DOPA: a precursor of catecholamines, an
important neurotransmitter used in the
treatment of Parkinson’s disease
Shikonin: used as an anti-bacterial and anti-
ulcer agent
Anthraquinone: used for dyes and medicinal
purposes

34. Opiate alkaloids: particularly codeine and
morphine for medical purposes
Berberine: an alkaloid with medicinal uses
for cholera and bacterial dysenterry
Valepotriates: used as a sedative
Ginsenosides: for medicinal purposes

35. Rosmarinic acid: for antiviral, suppression
of endotoxin shock and other medicinal
purposes
Quinine: for malaria
Cardenolides or Cardioactive glycosides: for
treatment of heart disease

36. Taxol: an example
Taxol is a unique anticancer drug from the
bark of the Pacific Yew (Taxus breviola)

37. Pacific Yew Facts
Pacific Yew was considered a trash tree by
foresters
The tree is slow growing, taking about 50
years to mature
It grows best in the understory of other trees,
not doing well in direct sunlight

38. Taxol Facts
Very effective treatment against ovarian
cancer, breast cancer, melanoma, and colon
cancer
Stops cell division, thus blocking cancer. It
does this by interfering with microtubule
function. Microtubules are responsible for
pulling apart the sets of chromosomes in
mitosis.

39. Taxol Needs
It is estimated that 250 kg of pure Taxol are
needed to treat cancer in the USA. This would
require the bark of about 360,000 trees per
year!
Obviously Taxol woud be very expensive by
this method (approximately $200,000 to
$300,000 per kg).

40. Taxol is a very good target for
biotechnology
a) tissue culture of bark cells
b) fungus produces taxol
c) alternative species
d) genetic engineering
e) chemical synthesis

41. a) tissue culture of bark cells
Many cells from different bark tissues from different
trees were screened.
There are at least 25 fold differences in production.
It was found to be secreted into the medium thus
facilitating collection.
So far 1 to 3 mg of taxol are produced per liter of
cell culture. This is equivalent to about 25 g of bark.

42. b) fungus produces taxol
It was found that a fungus that colonizes
yew trees also produces taxol
Fungal culture technology which is better
developed than plant cell culture technology
could be an important source for taxol
production

43. c) alternative species
Some researchers found that the European
Yew (Taxus baccata) produces a precursor
to taxol.
This precursor can then be converted to an
analog of taxol in the laboratory.
The precursor is used for chemical synthesis
of taxol.

44. d) genetic engineering
Other scientists are trying to identify and
clone the genes which produce taxol
This will enable them to scale up production
in cell culture

45. e) Chemical synthesis
Until 1994, chemical synthesis was
formidable
3 different ways to synthesize taxol are now
known
Some take up to 13 steps
Cost per patient still expensive; about
$20,000

46. This is because it usually takes 10 years of research to
produce a product. This requires that a product sell for at
least $400 per kg to make it economically worthwhile.

48. Many of these Third World countries may
lose market share to superior, more efficient
production of secondary metabolites in
industrial countries.
Is this right? Is it fair? Are third world
countries capable of competing? What
should they do?

49. THANKU