biosynthetic pathways

1. BIOSYNTHETIC PATHWAY OF
CARDIAC GLYCOSIDES
&
FLAVONOIDS
PRESENTED BY
G.SHOBHA RANI
M.PHARMACY(PHARMACOGNOSY)
CPS-IST-JNTUH.

2. CONTENTS
▪ CARDIAC GLYCOSIDES
INTRODUCTION
BIOSYNTHESIS OF CARDIAC GLYCOSIDES
▪ FLAVONOIDS
INTRODUCTION
BIOSYNTHESIS OF FLAVONOIDS

3. BIOSYNTHESIS
The production of a complex chemical compound from
simpler precursors in a living organism, usually involving
enzymes (to catalyze the reaction) and energy source
(such as ATP).
BIOGENESIS
Biogenesis is the production of new living organisms or
organelles.

4. CARDIAC GLYCOSIDES
⦿ Cardiac glycosides are a class of organic compounds
that increase the output force of the heart and increase
its rate of contractions by acting on the
cellular sodium-potassium ATPase pump.
⦿ Cardiac glycosides are found in a diverse group of
plants including
Digitalis purpurea & Digitalis lanata (fox gloves),
Nerium oleander (common oleander)
Urginea indica (squill) etc….

5. BASIC CHEMICAL STRUCTURE
The steroidal nucleus is “cyclopentano perhydrophenanthren”.

6. CLASSIFIED INTO
TWO CLASSES

7. EXAMPLES
⦿ Cardenolides have been primarily derived from the
foxglove plants Digitalis purpurea and Digitalis lanata
⦿ Bufadienolides have been derived from the venom of the
cane toad Bufo marinus.

8. BIOSYNTHESIS OF
CARDIAC
GLYCOSIDES

9. ⦿ The metabolic process of glycoside formation
involves 2 steps.
⦿ The 1st
part of biosynthesis is the formation of
aglycone part.(Formation of squalene through
mevalonate pathway).
⦿ The 2nd
part involves the coupling of aglycone
part with glycone part.(synthesis of cardiac
glycosides)

10. MEVLONATE PATHWAY

13. ⦿ Squalene is converted to oxidosqualene by the catalyzing action
of epoxidase.
⦿ Lanosterol is obtained by involvement of lanosterol synthase.
⦿ With the action of reductase demethylase oxidase it is
converted to cholesterol.
⦿ By the action of SCCE(stratum corneum chymotryptic enzyme)
cholesterol is converted to pregnenolone.
⦿ Pregnenolone is coverted to progesterone by the enzyme
dehydrogenase isomerease and it reduces to 5β-pregnan-3,
20-dione.
⦿ Resulting compound is converted to 3β hydroxy-5β
pregnan-20-one with the action of oxidoreductase.
⦿ It is hydrolyzed to 3β,14β,21-trihydroxy-5β-pregnan-20-one.
⦿ Digitoxigenin is formed by malonyl transferase.
⦿ It is hydrolysed to digoxigenin & gitoxigenin.
STEPS INVOLVED IN BIOSYNTESIS

14. BIOSYNTHESIS OF BUFADIENOLIDES
+C3 units Scillarennin
Scilliglaucosidin
hellebrigenin
Bufadienolides are synthesized by addition of 3 carbon
atoms to the pregnenolone moiety.
pregnenolone

15. STEP:2
COUPLING OF AGLYCONE WITH GLYCONE
MOIETY
⦿ Glucose-1-phosphate + UTP UDP-sugar + PP
⦿ UDP-Sugar + aglycone Glycoside + udp

16. BIOSYNTHETIC
PATHWAY OF
FLAVONOIDS

17. FLAVONIODS
⦿ Flavonoids – (Latin word flavus, meaning yellow, their color in
nature) are a class of plant and fungus secondary metabolites.
⦿ Flavonoids are widely distributed in plants, fulfilling many
functions.
⦿ Flavonoids are the most important plant pigments for flower
coloration, producing yellow or red/blue pigmentation in petals
designed to attract pollinator animals.
⦿ In higher plants, flavonoids are involved in UV filtration,
symbiotic nitrogen fixation and floral pigmentation.
⦿ They may also act as chemical messengers, physiological
regulators, and cell cycle inhibitors.

18. BASIC CHEMICAL STRUCTURES:

19. FLAVONOIDS
Flavanone (Eg:Hesperetin,Tangeretin)
Anthocyanin
(Eg:Delphinidine,Cyanidin)
Flavonol (Eg: Quercitin,Kaempferol)
Proanthocyanin (Eg: Polymeric
flavanols)
Flavanol (Eg: Epicatechin,Catechin)
Isoflavone (Eg: Genistein,Diadzein)
Flavone (Eg:Luteolin,Apigenin)

20. Schematic representation of
shikimic acid pathway

21. ⦿
SHIKIMIC ACID SYNTHESIS

22. The precursor for the biosynthesis of flavonoids is 4hydroxyl cinnamoyl
CoA, which is biosynthesize from phenyl alanine. phenyl alanine was
biosynthesized from shickimic acid pathway.

23. Schematic diagram of flavanoid biosynthetic pathway
⦿ CHI – chalcone isomerase
⦿ CHS – chalcone synthase
⦿ F3H – flavanoid
3-hydroxylase
⦿ DFR – dihyroflavonol
reductase
⦿ ANS – anthocyanidin
reductase
⦿ 3GT – glucose transferase

24. STEPS INVOLVED IN BIOSYNTHESIS
⦿ Flavanoids are synthesized by the phenylpropanoid metabolic
pathway.
⦿ The amino acid phenylalanine is used to produce
4-coumaroyl-coA.
⦿ 4-coumaroyl-coA is combined with malonyl-coA to yield the true
backbone of flavanoids, a group of compounds called
chalcones,which contain 2 phenyl rings.
⦿ Conjugate ring-closure of chalcones results in the famillier form of
flavanoids,the 3 reinged struture of flavone.
⦿ The metabolic pathway continues through a series of enzymatic
modifications to yield flavanones to dihydroflavanols to
anthocyanins.
⦿ Along this pathway,many preoducts can be formed,including the
flavonols,flavan-3-ols, proanthocyanidins(tannins) and a host os
other various polyphenolics.