Flavonoids come under the class of phenolic compounds.Phenolic groups consist of at least one benzene ring with one or more hydroxyl group.
Phenylpropanoids are naturally occurring phenolic compounds which contain three carbon side chains attached aromatic ring. They are biosynthetically derived from
phenylalanine (amino acid) which contains one or more C6-C3 residues.
CLASSIFICATION
1. Anthocyanins
2. Proanthocyanidins
3. Flavonols
4. Flavones
5. Glycoflavones
6. Biflavonyls
7. Chalcones and aurones
8. Flavonones
9. Isoflavones
PHYSICO-CHEMICAL PROPERTIES
• generally found in glycosidic form.
• They are water as well as alcohol soluble but some numbers are sparingly soluble like hesperidine or rutin.
• Aglycone part of the flavonoid glycosides are more frequently solubilize in polar solvent.
• The flavonoids which have lipophilic characteristic generally found in superficial tissue i.e. leaf can be separated with the help of medium polarity solvent like
dichloromethane then the other impurities like fats and waxes should be separated from this extract.
BIOLOGICAL PROPERTY
• Flavonoids or polyphenols are also well known for their free radicals scavenge activity which is formed under different conditions.
• Flavonoids also act as enzyme inhibitor for example histidine decarboxylase inhibits the naringenin or quercitin.
• Flavonoids are also useful as antiallergic, anti-inflammatory, hepatoprotective, maintains blood cholesterol level, diuretic, antispasmodic, antiviral or antibacterial.
• Some of them inhibit the growth of tumor or anticancer activity.
EXTRACTION OF FLAVONOIDS
Plant material
Extracted with boiling water create Crude extract .
Addition of lead acetate ,Tannins removed (in the form of lead salts) ,
After filtration Add water, Acidified with HCl, Boil for few hours
Precipitate of sugar free flavones or flavonones
Add alcohol for extraction and
Extract solution,
Purification of compound
Characterization of purified compound by using various spectroscopic techniques
CHEMICAL TESTS
1. Shinoda test: Upon addition of few magnesium turnings and conc. Hydrochloric acid (drop by drop) to the test solution, a pink scarlet, crimson red or sometimes
green to blue colour develops after some time.
2. Alkaline reagent test: When few drops of sodium hydroxide solution are added in the test solution, first sharp yellow colour develops which upon addition of dil. acid becomes colourless.
3. Zinc hydrochloric acid test: A mixture of zinc dust and l concentrated hydrochloric
acid is added in the test solution, it develops red colour after some time.
[I] TEA (click here)
[II] RUTA (click here )