• Flavonoids are a group of polyphenolic
compounds possessing 15 carbon
atoms, 2 benzene rings joined by a
linear 3 carbon chain having the carbon
• Flavonoids are found in fruits, flowers,
seeds & vegetables.
• Common in higher plants.
• Class of plant secondary metabolites.
According to their chemical structure
General Methods Of Structural Determination Of
• Ethanolic extract + pieces of magnesium fillings + few
drops of conc.HCl.
• Ethanolic extract + 10% NaOH. It gives yellow colour.
Change in colour from yellow to colourless on addition
to dil. HCl.
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.
Quercetin phloroglucinol protocatechuic acid
•Quercetin on boiling with alcoholic potash, it gives 6-OH, 2,4-
dimethylacetophenone & veratric acid.
• Organic chemistry of natural products by O P Agarwal, volume I, Pageno
• Organic chemistry of natural products by O P Agarwal, volume II,
• Organic chemistry, volume II, Stereochemistry & Chemistry of natural
products by I L Finar, 5th Edition, Pageno: 425.