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2. Group of polyphenoliccompounds which are found in fruits, flowers, seeds & vegetable.
They are more common in higher plants being abundant in families, Polygonaceae,
Rutaceae, Leguminosae, Umbelliferae & Compositae. Flavonoids (named fromthe Latin word
flavus meaningyellow, their colour in nature) are a class of plant secondary metabolites.
• Polyphenoliccompounds thatare foundeverywhere in nature and are categorized,
according to chemical structure, intoflavonols, flavones, flavanones, isoflavones, catechins,
anthocyanidins and chalcones
• Over 4,000 flavonoids have been identified, many of which occur in fruits,vegetables and
beverages (tea, coffee, beer, wine and fruitdrinks)

3. • The flavonoids have aroused considerable interest
recently because of their potential beneficial effects on
human health they have been reported to have
antiviral, antiallergic, antiplatelet, antiinflammatory,
antitumor and antioxidant activities.
Antioxidants are compounds that protect cells against the
damaging effects of reactive oxygen species, such as singlet
oxygen, superoxide, peroxyl radicals, hydroxyl radicals and
peroxynitrite.

4. The flavonoids are possessing 15 carbon atoms;two benzene rings joinedby a linear three
carbon chain the skeletoncan be representedas the C6 - C3 - C6 system.
The three-carbon (-C3-)may be included through an oxygen bond between the two phenyl
rings into:
1- A five-membered heterocyclicring (furan) as in aurones.
2- A six-membered heterocyclicring (pyran) to give flavonoids which constitute the
largest group.

5. Tea, Red wine, Apple,
Tomato, Cherry and Onion
Rutin, Myricetin,Flavonol
Tea andAppleCatechin, GallocatechinFlavanols
Thyme and ParsleyApigenin, ChrysinFlavones
Soya bean and other legumesGenistein, GlyciteinIsoflavones
Grape fruit and OrangeHesperidin, NarigeninFlavanones
Lemon and sour orangeTaxifolinFlavanonols
Flavonoids are present in photosynthesising cells and are commonly found in
• fruits • vegetables
• nuts • seeds
• stems, flowers, tea, wine, propolis and honey

6. The flavonoid aglycone consists of a benzene ring (A) condensed with a six
membered ring (C) pyran ring , which in the 2-position carries a phenyl ring
(B) as a substituent.
The flavonoid glycosides: Glycosides → aglycone (non sugar part)+glycone
(sugar part) When glycosides are formed, the glycosidic linkage can be located
in positions 3 or 7 and may be L-rhamnose, D- glucose, galactose or arabinose .

7. Flavonoidshave been reported to exert a wide range of biological activities.
These include:
• Antioxidant Activity
• Cardio-protective effects
• Anti-carcinogenic effects
• Gastro-protective effects
• Treatment of Inflammation
• Antimicrobial effects, and many more.

8. Oxidative damage could lead to a lot of degenerative diseases such as
artherosclerosis, hypertension, cataracts etc. which occurs when the electron
flow generates free radicals, such as O2- centred free radicals, known as reactive
oxygen species (ROS), and including superoxide (O2˙¯), peroxyl (ROO˙), alkoxyl
(RO˙), hydroxyl (HO˙) and nitric oxide (NO˙) radicals
Indeed, the phenolic groups of flavonoids serve as a source of a readily
available ‘‘H” atoms such that the subsequent radicals produced can be
delocalized over the flavonoid structure

9. Influence of FlavonoidsCardiovascular diseasesS/N
stress, inhibition of leucocyte leucocyte adhesion,
myeloperoxidase,
Artherosclerosis1
Decrease in oxidative stress.Arrhythmia2
Decrease in ROS burst, inhibition of platelet
aggregation
Acute Myocardialinfarction3
Decrease in oxidative stress (directROS scavenging)
inhibition of metalloproteinase
HeartFailure4
Vasodilatory properties, inhibition of NADPH
oxidase, recovery of NO due to inhibitionof
superoxide production
Hypertension5

10. Flavonoids are potent bioactive molecules that possess anti-carcinogenic effects
since they can interfere with the initiation, development and progression of
cancer by the modulation of cellular proliferation, differentiation, apoptosis,
angiogenesis and metastasis
Some molecular mechanisms of action of flavonoids are given
as follows :
•cell cycle arrest (p53 proteins)
• tyrosine kinase inhibition
• inhibition of heat shock proteins.

11. The mechanism of action responsible for the antiulcer activity of
flavonoids is their antioxidant properties, seen in garcinol, rutin
and quercetin.
It involves free radical scavenging, transition ,metal ions chelation,
inhibition of oxidizing enzymes, increase of proteic and nonproteic
antioxidants and reduction of lipid peroxidation

12. •A number of moulds and yeasts cause human and animal diseases. For example, species of
Aspergillus, Fusarium, and Sporothrixare opportunisticpathogens and easily infect
individuals with weak immune systems .
•An isoflavone found in a WestAfrican legume, alpinum isoflavone, prevents schistosomal
infection when applied topically .
•Antibacterial flavonoids having sugar moiety form complexes with proteins by forming either covalent
bond, hydrogen bond or hydrophobic effects.
Their mode of action may be related to their ability to inactivate microbial adhesions, cell envelope
transport proteins and others.
•Quercetin has been reported to completely inhibit growth of Staphylococcus aureus

13. There are no official dosages for bioflavonoids .
Doses in most supplements sold range from 30 to 200 milligrams
a day which is acceptable for general maintenance .
Clinical trials tend to be based on much higher doses of between 500 to
2000 mg (milligrams). For therapeutic purposes the range can be between
50 to 500 mg per day.

14. With the exception of green tea, research on flavonoids in general shows no
known toxic effects.
High doses do not appear to cause serious side effects, even for amounts as
high as 100 grams a day. Excess intake is simply excreted in urine.
The main symptom of flavonoid overdose is diarrhea.
As for green tea, highly concentrated doses of it might contain
too much caffeine for cancer and hepatitis patients, and for
those people sensitive to caffeine

15. Structure function relationship of flavonoids is epitome of major
biological activities.
Medicinal efficacy of many flavonoids as antibacterial, hepatoprotective,
anti-inflammatory, anticancer, and antiviral agents is well established.
Therapeutic use of new compounds must be validated using specific
biochemical tests.
Further achievements will provide newer insights and will certainly lead to a
new era of flavonoid based pharmaceutical agents for the treatment of
many infectious and degenerative diseases.