Biology Reference
In-Depth Information
lacking the HHDP group of
43
and
44
, and those such as casuariin and
desgalloylstachyurin, lacking the galloyl group of
45
and
46
.
Pterocarinin A with a lyxose residue and hippophaenin B with a
valoneoyl unit were found in
Pterocaria
species (Nonaka,
et al
., 1989)
and
Hippophae rhamnoides
(Yoshida
et al.
, 1991a),
respectively.
Elaeagnatin A from
Elaeagnus umbellata
(Ito
et al.
, 1999b) has both
lyxose and valoneoyl units in its structure.
R
3
O
O
R
2
Castalagin (
43
): R
1
= H, R
2
= OH, R
3
= (S)-HHDP
Vescalagin (
44
): R
1
= OH, R
2
= H, R
3
= (
S
)-HHDP
Castalin: R
1
= H, R
2
= OH, R
3
= H, H
Vescalin: R
1
= OH, R
2
= H, R
3
= H, H
R1
O
O
O
O
OH
HO
O
O
HO
OH
OH
HO
OH
O
H
OH
O
HO
M
OH
N
HO
HO
OH
OH OH
HOOC
HO
HO
OH
O
H
HO
O
O
O
HO
HO
OH
OH
O
O
R
2
R
4
O
R
1
Casuarinin (
45
): R
1
= R
4
= H, R
2
= OH, R
3
= G
Stachyurin (
46
): R
1
= OH, R
2
= R
4
= H, R
3
= G
Casuariin: R
1
= R
3
= R
4
= H, R
2
= OH
Desgalloylstachyurin: R
1
= OH, R
2
= R
3
= R
4
= H
Pterocarinin A: R
1
= M, R
2
= R
4
= H, R
3
= G
Hippophaenin B: R
1
= H, R
2
= OH, R
3
= G, R
4
= N
Elaeagnatin A: R
1
= M, R
2
= H, R
3
= G, R
4
= N
O
OR
3
O
O
OH
O
OH
OH
HO
OH
HO
2.1.5 Complex tannins (hybrids bearing a flavan-3-ol moiety)
Complex tannins, also called flavano-ellagitannins, are hybrid tannins
composed of a
C
-glycosidic ellagitannin [vescalagin (
44
) or stachyurin
(
46
)] and a flavan-3-ol (catechin or epicatechin). These two structural
units are bound through a C-C linkage between C-1 of the open-chain
glucose and C-8 or C-6 of the flavan-3-ol moiety. The (+)-catechin-
based complex tannins include stenophyllanins A (
47
) and B (
48
)
