Natural Products Big Class

1. III-Flavonoids
• Flavonoids are the secondary
metabolites produced in plants with a
significant role in human health
• They are a group of natural
substances with variable phenolic
structures found in fruits, vegetables,
grains, bark, roots, stems, flowers,
and tea.
• Flavonoids have 15-carbon skeleton
structures containing two phenyl rings
and a heterocyclic ring
• These natural products are well known
for their beneficial effects on health.
• Flavonoids are now considered as a
vital component in a variety of
nutraceutical, pharmaceutical,
medicinal and cosmetic applications
due to their anti-oxidative, anti-
inflammatory, anti-mutagenic and

2. Flavonoids are classified
into:
1- Flavonoids or
bioflavonoids, derived from 2-
phenyl chromen-4-one (2-
phenyl-1,4-benzopyrone)
structure
2- Isoflavonoids, derived from
3-phenyl chromen-4-one (3-
phenyl-1,4-benzopyrone)
structure
3- Neoflavonoids, derived
1
2
3

4. Biological effects
• Flavonoids are widely distributed in plants fulfilling
many functions, including producing yellow or red/blue
pigmentation in flowers and protection from attack by
microbes and insects.
• The widespread distribution of flavonoids, their variety,
and their relatively low toxicity compared to other active
plant compounds (for instance, alkaloids) mean that
many animals, including humans, ingest significant
quantities in their diet
• Flavonoids have been referred to as "nature's
biological response modifiers" because of strong
experimental evidence of their inherent ability to modify
the body's reaction to allergens, viruses, and
carcinogens.

5. • They show anti-allergic, anti-inflammatory, anti-
microbial, and anti-cancer activity.
• Consumers and food manufacturers have become
interested in flavonoids for their medicinal properties,
especially their potential role in the prevention of
cancers and cardiovascular disease.
• The beneficial effects of fruit, vegetables, tea, or even
red wine have been attributed to flavonoid compounds
rather than known nutrients and vitamins.

6. Quercetin
• Quercetin is a flavonoid, more specifically a flavonol,
that constitutes the aglycone of the glycoside rutin.
• In studies, quercetin is found to be the most active of
the flavonoids, and many medicinal plants owe much
of their activity to their high quercetin content.
• Quercetin has demonstrated significant anti-
inflammatory activity because of the direct inhibition
of several initial processes of inflammation.

7. • For example, it inhibits the production and release
of histamine and other allergic/inflammatory
mediators.
• In addition, it exerts potent antioxidant activity. It
has been found to be anti-cancer.
• Quercetin can be found in herbal products based
on Hawthorn, which are used for acute symptoms
of Congestive Heart Failure.

8. Epicatechin
Epicatechin improves blood flow and thus seems
good for cardiac health.
• Cocoa, the major ingredient of dark chocolate,
contains relatively high amounts of epicatechin
and has been found to have nearly twice the
antioxidant content of red wine and up to three
times that of green tea in in-vitro tests.
• But in the test outlined above, it now appears the
beneficial antioxidant effects are minimal as the
antioxidants are rapidly excreted from the body.

9. Oligomeric proanthocyanidins (tannins) (in
tea)
Proanthocyanidins extracts demonstrate a wide
range of pharmacological activity.
Their effects include
• increasing intracellular vitamin C levels
• decreasing capillary permeability and fragility
• scavenging oxidants and free radicals
• inhibiting the destruction of collagen, the most
abundant protein in the body.

10. Good sources of flavonoids
These include all citrus fruits, berries, onions,
parsley, legumes, green tea, red wine,
seabuckthorn, and dark chocolate (with a cocoa
content of seventy percent or greater).

11. Citrus
• The citrus bioflavonoids include hesperidin, quercetin,
rutin (a glycoside of quercetin), and tangeritin.
• In addition to possessing antioxidant activity and an
ability to increase intracellular levels of vitamin C, rutin
and hesperidin exert beneficial effects on capillary
permeability and blood flow.
• They also exhibit some of the anti-allergy and anti-
inflammatory benefits of quercetin.

12. • Quercetin can also inhibit reverse transcriptase,
part of the replication process of retroviruses.
• The therapeutical relevance of this inhibition has
not been established.
• Hydroxyethylrutosides (HER) have been used in the
treatment of capillary permeability, easy bruising,
hemorrhoids, and varicose veins.

13. Tea
• Green tea flavonoids are potent
antioxidant compounds thought to
reduce the incidence of cancer and heart
disease.
• The major flavonoids in green tea are
the catechins (catechin, epicatechin,
epicatechin gallate, and epigallocatechin
gallate (EGCG)).
• In producing teas such as black tea, the
leaves are allowed to oxidize, during
which enzymes in the tea convert some
or all of the catechins to larger
molecules.

14. • White tea is the least processed of teas and is
shown to present the highest amount of
catechins known to occur in Camellia Sinensis.
• However, green tea is produced by steaming the
fresh-cut leaf, which inactivates these enzymes,
and oxidation does not significantly occur.