Biology Reference
In-Depth Information
HO
H
from
α
fa
ce
O
O
HO
O
R
O
O
O
H
H
H
HO
H
O
HO
OH
O
OH
OH
O
HO
ascorbic
acid
from
β
face
O
OH
HO
O
OH
OH
OH
DHHDP group
from
β
face
from
α
face
- H
2
HO
HO
H
HO
O
O
HO
2
C
O
HO
HO
OH
O
O
OH
O
H
O
H
OH
O
O
O
O
H
OH
O
OH
OH
O
OH
HO
OH
OH
jolkinoyl group
elaeocarpusinoyl group
CO
2
O
H
O
O
H
HO
OH
O
OH
O
HO
putranjivainoyl group
OH
O
HO
HO
Fig. 4.11 Biogenesis of elaeocarpusinoyl, putranjivainoyl and jolkinoyl groups.
4.3.2 Similarities and differences between the oxidative dimerization
of the galloyl group and the pyrogallol-type catechin B-ring
In the biosynthesis of ellagitannins, it is generally accepted that the
HHDP group is derived from an oxidative coupling of two galloyl
groups (Gupta
et al.
, 1982). The presence of enzymes catalyzing the
reaction was recently evidenced (Niemetom
et al.
, 2005). Similar C-C
coupling of two pyrogallol rings also occurs during black tea production
