Biology Reference
In-Depth Information
accompanied by the trimer oenothein A and tellimagrandin I, the
monomer composing these oligomers (Hatano
et al.
, 1990a). Coriariin A
is the main component in
Coriaria japonica
(
Coriariaceae
) (Hatano
et al
., 1986). The monomers frequently found as constituents of these
oligomeric molecules are tellimagrandins I and II, pedunculagin and
casuarictin as further exemplified below by the structure of gemin A.
OH
HO
HO
OH
HO
HO
HO
HO
O
O
O
O
O
O
O
O
O
O
O
R
O
R
HO
HO
HO
O
O
O
O
HO
O
HO
HO
O
HO
HO
HO
OH
HO
OH
HO
OH
OH
OH
Tellimagrandin I : R = OH
Tellimagrandin II : R = (
β
)-OG
Pedunculagin : R = OH
Casuarictin : R = (
β
)-OG
Potentillin : R = (
α
)-OG
HO
HO
HO
OH
OH
O
OH
OH
O
O
HO
HO
O
O
O
OCH
2
O
O
O
OH
O
HO
O
OH
OH
O
O
O
O
O
O
OH
O
O
HO
O
O
OH
OH
HO
OH
HO
HO
HO
HO
OH
OH
OH
HO
OH
OH
Gemin A
1.3.4.2
Oligomerization via oxidative C-O and C-C coupling modes
The oligomerization of ellagitannins mainly occurs via C-O oxidative
coupling, but C-C oxidative coupling takes place in
C
-glycosidic
ellagitannins, including complex tannins. The C-O coupling modes can
be classified on the basis of the
O
-donating polyphenolic unit of a
monomer and the
O
-accepting polyphenolic unit in another monomer
composing the dimer, as shown below in Fig. 1.5. Generally, a given
