Flavan
Anthocyanidin
O
OH
O
H
OH
3-Deoxyafzalechin
2
3
4
4'
3'
5
7
O
OH
OH
OH
O
H
R
Pelargonidin R = H
Cyanidin R = OH
+
2
3
4
4'
3'
5
7
Flavonoid O-glycoside
OH
O
H
O
O
H
O
H
O
O
O
OH
OH
OH
OH
Quercetin 7-O-β-D-glucopyranoside
1''
6''
2
3
4
4'
3'
5
7
Flavonoid C-glycoside
O
H
OH
O
O
H
O
H
O
O
OH
OH
O
H
R
Isovitexin R = H
Isoorientin R = OH
1''
6''
2
3
4
4'
3'
5
7
Aurone
Proanthocyanidin
O
OH
O
H
O
O
H
OH
OH
OH
Amaronol A
O
OH
OH
OH
OH
O
OH
OH
OH
O
O
H
OH
OH
OH
O
H
O
H
O
H
O
H
Epicatechin trimer
Condensed tannin
Isoflavonoid
Biflavonoid
O
O
OH
R
O
H
Daidzein R = H
Genistein R = OH
O
O
OH
O
O
H
OH
O
Amentoflavone
6.7.5 Tannins
Plant polyphenols, also known as vegetable tannins, are a heterogenous
group of natural products widely distributed in the plant kingdom. Tannins
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CH6 NATURAL PRODUCT CHEMISTRY