FLAVONOIDS
Flavonoids in the broad sense of the term are virtually universal plant pigments. Almost
always water-soluble, they are responsible for the color of flowers, fruits, and sometimes
leaves.
• Phenolics
• Chromane skelaton
• 2-phenyl chroman:
Flavonoid
O
O 1
2 3 5 4
6 7
8
O
O 1
2 3 5 4
6 7
8
Prof. Dr. Gülçin Saltan İşcan, 1
Phenolics
• Phenols and phenolic acids
• Phenyl propanoids
• Flavonoids
• Anthocyanins
• Antraquinones
• Tannins
Classification of flavonoids
• Flavonoids fall into about some classes;
according to
• the bonding of the phenyl group in position 2 or 3 of the chromane ring,
• number and position of phenol group
• methyl ethers of phenol groups
• the genus and locality of the saccarides
Prof. Dr. Gülçin Saltan İşcan, 3
Flava : yellow
• When the OH number and PH increase, the yellow color becomes dark.
• When the OH number and PH decrease, the yellow color becomes lighter.
• The glycosidic forms of flavonoids are water-
soluble, insoluble in organic solvents.
O
O 1
2 3 5 4
6 7
8
O
O
2 1'
2' 3'
4'
6' 5'
O
O
Chromone:
benzo-γ- pyrone
Flavone: 2-phenylchromone
isoflavone
Prof. Dr. Gülçin Saltan İşcan, 5
Flavonol/flavan
O
O
OH
O
O
flavonole
Flavanone
(dihydroflavone)
Dihydroflavone/dihydroflavonol /flavan
The double bond between 2 and 3 is hydrogenated
dihydroflavonol
Prof. Dr. Gülçin Saltan İşcan, 7
Chalcones
O OH
2' 1' 3' 4'
5' 6' 1
2 3
4 5 6
Chalcones
Chalcones do not have a central heterocyclic nucleus
and are characterized by a three-carbon chain with a
ketone function and an α, β-unsaturation.
O OH
O O
CH 1
2 4 3
5 6
7
1'
2' 3'
4' 6' 5'
dihydrocalcones
Prof. Dr. Gülçin Saltan İşcan, 9
Aurones: gold color
Flavones
Chrysole: 5,7
dihydroxyflavone
• Populi Gemmae
O
O
1' 2'
3'
4'
6' 5'
OH
HO
Apigenin: 5,7,4’- trihydroxyflavone
• Fructus
Petroselini
O
OH O HO
OH
Prof. Dr. Gülçin Saltan İşcan, 11
Luteolin: 5,7,3’,4’-
tetrahydroxyflavone
• Lamiaceae- Compositae families
O
OH O HO
OH
OH
• Primulatine
• Acacetin
• Diosmetin
• Tricetalin
• Hipoletin
Prof. Dr. Gülçin Saltan İşcan, 13
C-methyl flavones
• Pinus strobus
O
OH O HO
H
3C
strobochyrisole
Flavones containing isophrenylation
• 3/6/8 C-
isophrenoids
• Artocarpus heterophyllus
O
OH O HO
HO OH
2' 4'
7
6 5
artocarpesol
Prof. Dr. Gülçin Saltan İşcan, 15
O
OH O HO
6 3
O
OH O HO
6 3
OH
OH
Mulberrin (Morus
alba) Rubraflavone C (Morus
The isophrenoid unit constitutes the ring
• Pyran ring
O
OH O
OH
OH
O 7
Rubraflavon D
Prof. Dr. Gülçin Saltan İşcan, 17
Flavone + other ring system
O
OCH
3O
O O
OCH
3O HO
N CH
3Furanoflavone (pinnatol)
Flavonoidal alkaloid
(ficine)
Flavonols
• Flavons bearing OH in 3 C
• contains OH in positions 5 and 7
O
O
OH
Prof. Dr. Gülçin Saltan İşcan, 19
Classification according to OH groups in ring B
a) Flavonols that do not carry OH in B-ring
• Galangin (5,7-
dihyroxy flavonol) O
O
OH OH
HO
b) Flavonols that carries 1 OH in B-ring
• Kaempferol (5,7,4’-
trihydroxyflavonol
) O
O
OH OH
HO
OH 4'
Prof. Dr. Gülçin Saltan İşcan, 21
c) Flavonols that carries 2 OH in B-ring
• Quercetin (5,7,3’,4’- tetrahydroxyflavonol)
O
O
OH OH
HO
OH 4' OH
3'
d) Flavonols that carries 3 OH in B-ring
O
O
OH OH
HO
OH OH
OH
Prof. Dr. Gülçin Saltan İşcan, 23
• Mircetin
some OH groups may be esterified
e) Flavonols that carries ON in 6, 8 , 6 & 8
O
O
OH OH
HO
OH
HO
Galetol (6 C) Prof. Dr. Gülçin Saltan İşcan, 25
O
O
OH OH
HO
CH
3O OH
CH
3O
Limocitrin (8 C)
O
O OCH 3
OCH 3
OCH 3
CH 3 O CH 3 O
5
f) 5 veya 7 deoksi flavonoller
Aurenetol (5-deoksi)
Prof. Dr. Gülçin Saltan İşcan, 27
GLYCOSYLFLAVONOIDS
• The sugar moiety may be mono-, di-, or trisaccharide.
• Monosaccharides include D-glucose, D- galactose, D-glucuronic or D-
galacturonic acid.
• Structural variability expands in the glycosides formed with disaccharide.
They formed pyranose or furanose
forms.
GLYCOSYLFLAVONOIDS also contain;
• Organic acids:
• Coumaroic acid
• Ferulic acid
• Caffeic acid
• Gallic acid
Prof. Dr. Gülçin Saltan İşcan, 29
Most common
glycosylflavonoids
Flavones
Apigenin+glucose+apiose=Apioside Luteolin+glucose+glucose=Gluteoilin Flavonols
Kaempferol+glucose+glucose=Kaempfero side
Qurcetin+ramnse=Quercitrin
C-glycosylflavonoids
• Resistant to acid hydrolise
O
O Glikoz
OH
OH
HO
Vitexin (C-glycoside)
Prof. Dr. Gülçin Saltan İşcan, 31
• Saponarin
•
•
O
OH O
OH
Glikoz- O
Glikoz
• Xysilosile orientin
O
OH O
OH
HO
Glikoz-ksiloz
OH
Prof. Dr. Gülçin Saltan İşcan, 33
Chalcone,dihydrochalcone and aurones
• Chalcones and aurones are usually invisible, and turn orange and red,
respectively, in the
presence of ammonia vapors.
• Chalcones do not have a central heterocyclic
nucleus.
O OH
2' 1' 3' 4'
5' 6' 1
2 3
4 5
6
A
B
Chalcone
Chalcones
• B ring is fairly often unsubstitued
• B ring containing 1 OH
• B ring containing 2 OH
• B ring containing 3 OH
Prof. Dr. Gülçin Saltan İşcan, 35
Dihydrochalcones
O
OH 1 2
3
4 5 A 6
B
Aurones
O O
CH 1
2 4 3
5 6
7
1'
2' 3'
4' 6' 5'
A B
Prof. Dr. Gülçin Saltan İşcan, 37
Xanthones and dibenzopyranes
1 2 3 4 5
6 O
7
8
O
O
O HO
OH
OCH
3Xantone Gentisin
BIFLAVONOIDS
• Flavonoids can also bond to one
another, particularly through their very reactive C-6 or C-8. The result is a
dimer known as a biflavonoid.
Prof. Dr. Gülçin Saltan İşcan, 39
O OH
2' 1' 3' 4'
5' 6' 1
2
3 4
5
6
OH
OH HO
Naringenin chalcone
When a electron removed from C-4’, a radical occur.
O OH
O*
OH HO
Prof. Dr. Gülçin Saltan İşcan, 41
• This radical has many canonical forms.
• The majority of natural
biflavonoids are dimers of flavones and flavonols, are
generally 5,7,4’-trisubstituted.
O OH
O*
OH HO
O OH
OH HO
* O
O OH
OH HO
O
*
O OH
OH
O *
alfa
beta
Prof. Dr. Gülçin Saltan İşcan, 43
Classification of biflavonoids
• Oknaflavone (α-ß)
• Hinociflavone
• Robustaflavone
• Amentoflavone
• Garciniabiflavonoid
• Agatisflavone
• Cupresciflavone
O
OR3
R2O O
R1O
O
O R4O
OR5
O O
O HO
OH
O
O OH
HO
oknaflavone OH
hinokiflavone
Prof. Dr. Gülçin Saltan İşcan, 45
Flavanone and dihydroflavonols
• Not available as nature
• The common form is 7-OH flavonole
O
O
Isoflavonoids
• Isoflavonoids are characterized, like flavonoids, by a C15 skeleton Ar-C3-Ar type, but one which is now rearranged to be a 1,2- diphenypropane: all
molecules in this group can be releated to the skeleton of 3-
phenylchromane.
Prof. Dr. Gülçin Saltan İşcan, 47
Classification of isoflavonoids
• 1. Isoflavanes
• 2. Isoflavanones
• 3. Rotenoids
• 4. Pterocarpanes
• 5. Coumestanes
• 6. Others
O
O
O
O O
isoflavone
isoflavanone
isoflavan
Prof. Dr. Gülçin Saltan İşcan, 49
O
O
O
O
O
O O
O
O
O
Rotenoid
Pterocarpan
O
O OH
OH HO
O
O OH
OH
HO O
OH OH
HO CH
3O
O
O
O O
OCH
3OCH
3O
O
O
OH HO
Genistein
Licoricidine
Coumestan Rotenone
Prof. Dr. Gülçin Saltan İşcan, 51
Anthocyanins
• The term
anthocyanin, initially coined to designate the substance
responsible for the color of the
cornflower (anthos:
flower; kuanos:
blue)
• Water soluble pigments
responsible for the red, pink,
mauve, purple, blue, or violet
color of the most flowers and
fruits.
Anthocyanins
• These pigments occur as glycosides (the
anthocyanins), and their aglycones (the
anthocyanidins) are derived from the 2-
phenylbenzopyrylium cation, more commonly refered to as the flavilium cation, a name that emphasizes the fact that these molecules belong to the vast group of flavonoids in the broad
sense of the term.
• Rare in Gymnosperms, anthocyanins are found in all of the
Angiosperms
Prof. Dr. Gülçin Saltan İşcan, 53
O +
2-fenil benzopirilyum (Flavilium)
O +
Benzopirilyum
O +
2-fenil benzopirilyum (Flavilium)
O +
3-hidroksi flavilium(Antosiyanidol)
OH
O +
Siyanidol
OH
OH OH
OH HO
O +
Delfinidol
OH
OH OH OH
OH HO
O +
Pelargonidol OH
OH
OH HO
Prof. Dr. Gülçin Saltan İşcan, 55
3-deoxy anthocyanidins are relatively stable.
O +
Luteolinidol
OH
OH HO
OH
O +
Apigeninidol
OH
OH
HO
Antocyanins
• Anthocyanidins occur in acidic medium as
cations. They are
always hydroxylated at C-3 or C-5 and the oses bond from this
positions.
O +
3 OH 5
ChemDraw Ultra 6.0.lnk
