Biology Reference
In-Depth Information
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Gramicidin S Gramicidin S + sanguiin H-6
Fig. 4.6 Partition of gramicidin S in the presence of sanguiin H-6.
: gramicidin S in
5% DMSO-buffer solution (2 mg/ml) was partitioned with
n
-octanol at 26 °C and the
n
-
octanol layer was analyzed by HPLC.
: same experiment performed in the presence of
sanguiin H-6 (21, 2 mg/ml).
4.2.3 Self-association and biogenesis of dimeric ellagitannins
The self-association of 1-
O
-galloylpedunculagin in an aqueous solution
was found to be regioselective (Tanaka
et al.
, 1997b). The corresponding
1
H-NMR spectra measured in D
2
O showed a large up-field shift of the
glucose H-5 signal when the concentration was increased (Fig. 4.7). At
the same time, the aromatic proton of the 2,3-HHDP pyrogallol ring
connected to the 2-position of the glucose core was shifted to a lower
field. The Δδ values were concentration-dependent at concentrations
lower than 0.01 M. This result is indicative of the occurrence of a
regioselective self-association, and the large Δδ values of H-5
suggested that this proton is shielded by the aromatic ring of another
molecule. From an analogy with the case of pentagalloylglucose
(PGG,
8
, see Fig. 4.4), it was deduced that the O-1 galloyl group of 1-
O
-
