FLAVONOIDS
Presented by,
ASWINI SASIDHARAN
FIRST SEMESTER M.PHARM
PHARMACEUTICAL CHEMISTRY

Contents
• Introduction
• Classification
• Isolation
• General method of structural determination.
• Structural elucidation of quercetin

• Flavonoids are a group of polyphenolic
compounds possessing 15 carbon
atoms, 2 benzene rings joined by a
linear 3 carbon chain having the carbon
skeleton C6-C3-C6.
• Flavonoids are found in fruits, flowers,
seeds & vegetables.
• Common in higher plants.
[Leguminosae, Rutacea].
• Class of plant secondary metabolites.
Introduction

Classification
According to their chemical structure
Flavone
Apigenin
Luteolin
Tangeritin
Diosmetin
Flavonol
Rutin
Myricetin
Quercetin
Quercetrin
Flavanone
Hesperetin
Naringenin
Eriodietyol
Flavanonol
Taxifolin
Dihydro Kaempferol

APIGENIN LUTEOLIN MYRICETIN
QUERCETIN
HESPERETIN
NARINGENIN

TAXIFOLIN DIHYDROKAEMPFEROL

Isolation Of Flavonoids

General Methods Of Structural Determination Of
Flavonoids
Shinoda Test
• Ethanolic extract + pieces of magnesium fillings + few
drops of conc.HCl.
Sodiumhydroxide Test
• Ethanolic extract + 10% NaOH. It gives yellow colour.
Change in colour from yellow to colourless on addition
to dil. HCl.

FLAVONES
• Doesnot have OH group.
• On fusion with alkali, degrades to phenol & aromatic acid.

Flavones on boiling with KOH gives 4 different products.
+
+
Salicylic acid
acetophenone
o-hydroxyacetophenone
benzoic acid

o-hydroxyacetophenone
Flavone
o-hydroxyacetophenone

Flavonols
• It contains one hydroxyl group.
• On boiling with KOH, it yield o-hydroxybenzoyl methanol & benzoic acid,
it indicates the flavonol is 3-hydroxy flavone.

•Finally the structure is confirmed by Robinsons Method.

Structural Elucidation Of Quercetin
• It have 5 hydroxyl group.
• It forms pentaacetyl & pentamethyl groups.
• It gives Shinoda test to form yellow or red colour.
• It reduces Tollen’s reagent to give a silver mirror.

• On fusion with KOH, it produces phloroglucinol & protocatechuic acid.
• It indicates that quercetin is 5,7,3,4- tetrahydroxy flavonol.
KOH
Quercetin phloroglucinol protocatechuic acid
I I

•Quercetin on boiling with alcoholic potash, it gives 6-OH, 2,4-
dimethylacetophenone & veratric acid.
Quercetin
2,4-dimethylacetophenone
veratric acid

Kostaneck’s Synthesis
2,4-dimethoxyacetophenone 3,4-dimethoxybenzaldehyde

REFERENCES
• Organic chemistry of natural products by O P Agarwal, volume I, Pageno
:350-406.
• Organic chemistry of natural products by O P Agarwal, volume II,
Pageno :2.1-2.4.
• Organic chemistry, volume II, Stereochemistry & Chemistry of natural
products by I L Finar, 5th Edition, Pageno: 425.

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