Detailed study of Flavonoids including its Definition, properties, types, classification, isolation/extraction

1. FLAVONOIDS

2. • Class of plant secondary metabolites
• Word Flavonoids derived from latin word:
“Flavus”= yellow
• Group of polyphenolic compounds which are
found in fruits, flowers, seeds & vegetable

3. Structure of flavonoids: The flavonoids are
possessing 15 carbon atoms; two benzene rings
joined by a linear three carbon chain the skeleton
can be represented as the C6 - C3- C6 system.

4. Physiological role:
1- Role in plant defense mechanism:- They have
a very limited role in this respect due to their low
toxicity when compared with other plant
secondary metabolites such as alkaloids.
2- They are the pigments of flowers and attract
pollinating insects.
3- They play a role in plant growth control by
inhibiting & activating enzymes.

5. Physical Properties
1. Crystalline solids, sharp Melting point
2. Solubility: in H2O & alcohol (Flavonoid glycoside). Non
glycosidic flavonoid: Aglycone part-sol. in organic solvents
3. Color: Flavonones, Flavanol, Isoflavones-
Colorless: Flavonols, Flavones: Yellow, Chalchones, aurones:
Yellow Orange
4. Anthocyanidin : Red, blue, Purple
5. optically active

6. Chemical properties
• 15 C skeleton, 2 benzene linked by heterocyclic
pyran ring
• Being phenolic, dissolves in alkalies →Yellow
sol. +HCl → colorless
• Glycosidic linkage located at 3 or 7 C
• Flavanones, Flavonones are unstable compound ,
on oxidation → Chalcones, leucocyanidines
• Flavonoid + FeCl3→ green/ purple/ red to brown
color

7. CLASSIFICATION
• The three-carbon (-C3-) may be included through
an oxygen bond between the two phenyl rings
into:
• A five-membered heterocyclic ring (furan) as in
aurones.
• A six-membered heterocyclic ring (pyran) to give
flavonoids which constitute the largest group. The
flavonoid aglycone consists of a benzene ring (A)
condensed with a six membered ring (C) pyran
ring, which at 2nd position adds a phenyl ring (B)
as a substituent. C6-C3-C6 structure

10. 1. Flavones (2-phenylchromen-4-one): Have a double bond
between positions 2 and 3 and a ketone in position 4 of the
C ring.
ex:- Apigenin, Luteolin
2.Flavonols: Have a hydroxyl group in position 3 of the C
ring, which may also be glycosylated.
Ex: Kaempferol, Rutin, Myricetin, Quercetin.
3. Flavanones: Have C ring saturated; the double bond
between positions 2 and 3 is saturated,
ex:Hesperetin, Hespereidin, Naringenin
4. Flavanonols : ex:Taxifolin, Silymarin

11. 5. Isoflavones and Neoflavonoids ids can be
regarded as abnormal flavonoids.
6. Flavanols Ex: Catechin
7. Anthocyanidins : Anthocyanidins are common
plant pigments. Color of the anthocyanins
depends on pH.
8. Chalcones and dihydrochalcones

12. CHEMICAL TESTS

14. ACTIONS OF FLAVONOIDS
1-Flavonoids as antioxidants: The flavones and
catechins seem to be the most powerful
flavonoids for protecting the body against
reactive oxygen species (ROS).
2- Anti ulcer effect: Majority of peptic ulcers
are associated with helicobacter pylori,
Quercetin seems to play a very important role in
the prevention and treatment of peptic ulcer.

15. 3- Anti atherosclerotic effects: Flavonoids seems
to suppress LDL oxidation and inflammatory
progression in the artery wall.
4- Anti-inflammatory effect: flavonoids like
quercetin are shown to inhibit the
cyclooxygenase pathway. This inhibition reduces
the release of arachidonic acid.

16. 5-Hepatoprotective activity: Many flavonoids have
also been found to possess hepato-protective
activity e.g silymarin, apigenin, quercetin and
naringenin.