Biology Reference
In-Depth Information
2.1.1 Primary ellagitannins (HHDP esters)
In addition to the basic ellagitannins
1
and
4
, which have a
4
C
1
glucose
core, and their deacylated congeners, strictinin (
2
), gemin D (
3
),
pedunculagin (
5
), and isostrictinin (
6
) (Okuda
et al.
, 1980b, 1983,
Yoshida
et al.
, 1985), many naturally occurring analogs exist, such as
rugosins A (
10
) and B (
11
)
(Hatano
et al.
, 1990a), tirucallin A (
12
,
Yoshida
et al.
, 1991b), cornusiin B (
13
, Okuda
et al.
, 1984a), praecoxins
C (
14
) and D (
15
) (Hatano
et al.
, 1991) and tergallagin (
16
, Tanaka
et al.
, 1986a), in which a HHDP or a galloyl group is replaced by a
valoneoyl, a depsidone, a tergalloyl, or a gallagyl group.
HO
OH
HO
HO
HO
OH
HO
O
OH
HO
Tircallin A (
12
): R = (
β
)-OG
Cornusiin B (
13
): R = OH
HO
COOH
HO
O
O
O
HO
O
O
HO
O
O
GO
O
HO
O
O
R
O
R
O
O
O
O
OH
OG
G
HO
Rugosin A (
10
): R = (
β
)-OG
Rugosin B (
11
): R = OH
O
HO
HO
OH
O
OH
OH
O
HO
OH
HO
O
OH
OH
OH
O
HO
HO
O
O
O
O
HO
O
Praecoxin C (
14
): R = (
β
)-OG
Praecoxin D (
15
): R = OH
O
O
O
HO
HO
O
O
OH
O
O
OH
OH
HO
HO
O
O
O
O
O
R
O
O
HO
HO
O
O
O
HO
OH
O
OH
HO
HO
Tergallagin (
16
)
OH
OH
OH
HO
OH
HO
O
O
OH
The tannins possessing a valoneoyl group or its regioisomer, the
tergalloyl group, may be produced by the catabolism of oligomeric
ellagitannins in a plant (
vide infra
). However, the possibility that they
could be formed in an anabolic manner through oxidative coupling of the
O