Agriculture Reference
In-Depth Information
Hydrolysable tannins
O
OH
OH
O
HO
OH
OH
O
OH
HO
HO
HO
OH
OH
O
O
HO
HO
OH
OH
O
O
OH
(c) Gallic acid
(a) Hexahydroxydiphenic acid (HHDP)
(b) Ellagic acid
OH
O
HO
OH
OH
OH
O
HO
OH
OH
O
O
OH
O
OH
HO
O
O
O
O
O
OH
O
O
O
O
O
HO
O
O
O
O
OH
O
O
O
HO
OH
O
HO
OH
HO
HO
OH
HO
OH
OH
HO
H
OH
HO
OH
(d) Sanguiin H-6
HO
OH
O
OH
HO
RO
R
1
OH
OH
HO
(e) Stilbene monomers
R
1
= H, R = H:
trans
-resveratrol; R = glucoside:
trans-
piceid
R
1
= OH, R = H:
trans-
piceatannol; R = glucoside:
trans-
astringin
(f)
ε
-Viniferin
Fig. 9.2.
Structure of some non-fl avonoid polyphenols found in fruits.
to extraction from the rind) in pomegranate
where they are represented mostly by
punicalagins and ellagic acid (Gil
et al.
,
2000). Rather high levels (360-910 mg
kg
-1
) of ellagitannins have also been
reported in muscadine grape (Lee
et al.
,
2005).
9.2.3 Other polyphenols
Stilbenoids, often called stilbenes, are
polyhydroxystilbenes (C6-C2-C6), that is,
hydroxy and methoxy derivatives of
stilbene (1,2-diphenylethylene), as well as
their glycosides and polymers. Stilbenes
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