Biology Reference
In-Depth Information
The visible absorption band of both anthocyano-ellagitannins
39
and
40
recorded in aqueous solutions at pH 1 and 3.2 (
i.e.
, wine pH) indeed
revealed an important bathochromic shift of about 20 nm with respect to
that of malvidin (
37
) or oenin (
38
) (Fig. 9.15). The respective bright red
and deep purple colors of acidic (pH 1) aqueous solutions of pure
38
and
40
are clearly seen on the pictures inserted in Fig. 9.14.
OMe
OH
8
HO
O
2
OMe
OR
flavylium
forms
OH
37
: R = H, malvidin
38
: R =
β
-
D
-glucose, oenin
+H
+
/-H
2
O
OMe
OH
OH
8
HO
O
OMe
+H
+
/-H
2
O
OR
1
[
27
]
hemiketal
forms
OH
H
2
O
OMe
HO
HO
H
HO
OH
OR
MeO
HO
O
O
H
HO
O
OH
O
O
HO
8
1
O
HO
O
O
O
OH
HO
O
O
HO
OH
HO
39
: R = H, malvidin-8-
C
-vescalagin (25%)
40
: R =
β
-
D
-glucose, oenin-8-
C
-vescalagin (3%)
OH
OH
HO
Fig. 9.14 Hemisynthesis of malvidin-8-
C
-vescalagin (
39
) and oenin-8-
C
-vescalagin (
40
)
from vescalagin (
1
) and malvidin (
37
) or oenin (
38
), respectively, in an acidic organic
medium (isolated yield, see text).
HO
