Flavonoids

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By - Jaspreet Rekhi www.rhombnet.com
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Flavonoids

• The flavonoids are polyphenolic compounds
  possessing 15 carbon atoms two benzene rings
  joined by a linear three carbon chain having the
  carbon skeleton C6 - C3 - C6 and they are the
  plant pigments and they are having polar in
  nature and solouble in methanol and water.
• Flavonoids constitute one of the most
  characteristic classes of compounds in higher
  plants. Many flavonoids are easily recognised as
  flower pigments in most angiosperm families
  (flowering plants).
• However, their occurence is not restricted to
  flowers but include all parts of the plant.
• They are secondary mettabolite and effective in
  CNS disorders.

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Tests for flavonoids

• The extracts were dissolved in ethanol, filtered
  and subjected to following tests.
• Shinoda test The dried extracts were dissolved
  in 95 ethanol (5ml) and few drops of
  concentracted hydrochloric acid (HCL) were added.
  Then the magnesium turnings were put into the
  solution and observed for appearance of pink
  color.
• Lead acetate solution test To small quantity of
  above residue, lead acetate solution was added
  and observed for appearance of formation of
  yellow colored precipitates.

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The Most Important Classes of Flavonoids and their Biological Significance The Most Important Classes of Flavonoids and their Biological Significance The Most Important Classes of Flavonoids and their Biological Significance
class number of known members biological significance (so far as known)
anthocyanin(s) 250 red and blue pigments
chalcons 60 yellow pigments
aurones 20 yellow pigments
flavones 350 cream-coloured pigments of flowers
flavonols 350 feeding repellents (?) in leaves
dihydrochalcons 10 some taste bitter
proanthocyanidins 50 astringent substances
catechins 40 some have propertieslike those of tannins
isoflavonoids 15 oestrogen effect, toxic for fungi
Flavonoids

• Polyphenolic compounds with 15 C atoms, 2
  benzene rings on linear 3 C chain
• Over 4,000 flavonoids
• Easily recognized as flower pigments in most
  angiosperm plants but are not always flower
  pigments
• In plants they repair damage and shield from
  environmental toxins

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Core structures and nomenclature

• The nomenclature of flavonoids proper is
  straight-forward with the aromatic ring A
  condensed to the heterocyclic ring C and the
  aromatic ring B most often attached at the C2
  position. The various substituents are listed
  first for the A and C ring and - as primed
  numbers - for the B ring (note that the numbering
  for the aromatic rings of the open-chained
  precursor chalcones is reversed).
• (Harborne JB, ed. (1988) The Flavonoids. Advances
  in Research. Chapman Hall.)

Flavonoids
Society For Free Radical Biology and Medicine
W. Bors et al. .5
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Flavonoids there example

• Flavone- Luteolin, Apigenin, Tangeritin
• Flavonol- Quercetin, Kaempferol, Myricetin,
• Fisetin, Isorhamnetin,
• Pachypodol, Rhamnazin
• Flavanone- Hesperetin, Naringenin,
• Eriodictyol,
  Homoeriodictyol
• Flavanonol- Taxifolin, Dihydrokaempferol

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Other flavonoids

• CHALCONE
• Chalcone is derived from three acetates and
  cinnamic acid as shown below.
• Anthocyanidin is an extended conjugation made up
  of the aglycone of the glycoside anthocyanins.
  Next to chlorophyll, anthocyanins are the most
  important group of plant pigments visible to the
  human eye.

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• The anthocyanodins constitute a large family of
  differently coloured compounds and occur in
  countless mixtures in practically all parts of
  most higher plants. They are of great economic
  importance as fruit pigments and thus are used to
  colour fruit juices, wine and some beverages.
• The anthocyanidins in Hydrangea, colours it RED
  in acid soil and BLUE in alkali soil.

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ISOLATION OF FLAVONOIDS
Ground plant material

• Maceration (3 times)
• Purification with Chloroform (3 times)
• Dropwise addition of 10 NACL solution
• and centrifugation

Aqueous layer
Aqueous layer
Flavonoids in supernant liquid
Precipitate of tannins
Partioning with ethyl acetate
Flavonoid obtained by evaporation of
ethylacetate layer
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Flavonoids

• Act like antioxidants. How effective they are
  depends on their molecular structural
  characteristics
• Some flavonoids in hops and beer have been
  found to have better antioxidant effects than tea
  or red wine most flavonoids are found in fruits,
  vegetables, teas, and other drinks.
• Flavonoids have been known to have antiviral,
  anti-allergic, antiplatelet, anti-inflammatory,
  antitumor and antioxidant activities

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• Many flavonoid containing plants are
• Diuretic.
• Antispasmodic.
• Diaphoretic.
• Increase tensile strength of capillary walls.
• Free radical scavengers.

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By - Jaspreet Rekhi www.rhombnet.com
www.ppt.rhombnet.com