Communications
two-enzyme cascade for economic synthesis of resveratrol 3,5-
diglucoside. Up to 5.4 gLÀ1 diglucoside was produced from
two inexpensive substrates (piceid and sucrose) with only cata-
lytic amounts of UDP (Figure S7). The kinetic data for
UGT71A15 (Figure S6) suggest increasing the piceid concentra-
tion (up to ~40 mm), where substrate inhibition of the enzyme
becomes effective, as one possible strategy for improving the
transformation further. A plausible strategy to cope with the
requirement for high amounts of UGT71A15 is the reuse of im-
mobilized enzyme.
troloside compared with resveratrol in either antioxidant assay
used (Figures S8 and S10). The results clearly underline site se-
lectivity as critical in the enzymatic glucosylation of piceid; this
is required for development of a resveratrol derivative exhibit-
ing a desirable combination of high water solubility and similar
antioxidant properties.
In conclusion, a highly efficient single-step synthetic route
to resveratrol 3,5-diglucoside from piceid is reported here for
the first time. Glucosyltransferase UGT71A15 was identified as
a perfectly selective catalyst of the reaction. The 3,5-digluco-
side was shown to be an interesting water-soluble resveratrol-
based antioxidant. It might also constitute a bioavailability-en-
hanced potential prodrug.[17a] Piceid is more soluble than re-
sveratrol but it is easily hydrolyzed. The 3,5-diglucoside by con-
trast is more resistant to enzymatic hydrolysis.[17a] 3,5-Digluco-
side has been obtained by chemical[17a,b,28,30] and enzymatic
procedures.[23f, h] However, all these are unselective, thus result-
ing in complex mixtures of products from which the target di-
glucoside has to be isolated through elaborate workup proto-
cols. Moreover, chemical synthesis involves a multistep proto-
col. Clearly, the yield of resveratrol 3,5-diglucoside is seriously
limited in synthetic routes and previous biotransformations.
The convenient access to the 3,5-diglucoside by simple regio-
specific enzymatic production from piceid enables the 3,5-di-
glucoside to be evaluated more broadly in different applica-
tions: its use as a resveratrol prodrug is particularly promis-
ing.[17a]
About 23 mg of resveratrol 3,5-diglucoside was recovered
from conversions of 5 mm piceid on a 10 mL scale by using re-
versed-phase HPLC, with an isolated yield of 90% based on
piceid. Product purity was ~99% (based on HPLC peak area),
and product identity was confirmed by comparison with previ-
ously reported NMR data.[23h,28] Resveratroloside was recovered
from the more complex product mixture of the resveratrol re-
action (Supporting Information).
3,5-Diglucoside was compared with piceid, resveratroloside,
and unglucosylated resveratrol (reference) for water solubility
and antioxidant activity (Table 1). Attachment of a single gluco-
syl residue to resveratrol resulted in moderately enhanced sol-
ubility, irrespective of the site of glucosylation. Double glucosy-
lation of the resorcinol moiety of resveratrol, by contrast, was
extremely effective in increasing the water solubility, by more
than 4000-fold in terms of mass concentration. On a molar
basis, resveratrol availability in aqueous solution was thus en-
hanced around 1700-fold or 100-fold when compared to re-
Acknowledgement
Table 1. Solubility and antioxidative power of resveratrol and its gluco-
sides.
Financial Support from the EU FP7 project SuSy (Sucrose Syn-
thase as Effective Mediator of Glycosylation) is gratefully ac-
knowledged.
Substrate
Water solubility[a]
DPPH
IC50 [mm][b]
FRAP
FE[c]
gLÀ1
mm
resveratrol
piceid
resveratroloside
3,5-diglucoside
0.04
1.26
1.42
172
0.18
3.23
3.62
311
46.7
59.3
>1790
128.5
1.02
0.91
0.16
0.89
Keywords: antioxidants
· enzyme catalysis · glycosides ·
glycosyltransferases · resveratrol
[a] After 48 h incubation at 308C; [b] Concentrations required for scav-
enging 50% DPPH after 60 min; [c] Ferrous equivalents (mmol Fe2+ pro-
duced per mmol of antioxidant after 30 min).
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[2] a) A. Scalbert, G. Williamson, J. Nutr. 2000, 130, 2073S–2085S; b) S. Qui-
[3] a) P. C.-T. Tang, Y.-F. Ng, S. Ho, M. Gyda, S.-W. Chan, Pharmacol. Res.
sveratrol or piceid, respectively.
Antioxidant activity was assessed by radical-scavenging and
one-electron-reducing abilities, by applying the DPPH (2,2-di-
phenyl-1-picrylhydrazyl) and FRAP (ferric ion reducing antioxi-
dant power) assays widely used to evaluate the antioxidative
power of polyphenols.[29] Both assays gave consistent results,
thus showing that glucosylation of the resorcinol moiety of re-
sveratrol caused only a relatively small loss of antioxidant activ-
ity compared to the unglucosylated reference resveratrol. Glu-
cosylation of the styryl moiety, by contrast, resulted in a dra-
matically decreased antioxidant activity, reflected not only in
a highly increased IC50 value in the DPPH assay and decreased
ferrous equivalents (FE) value in the FRAP assay, as shown in
Table 1, but also in a greatly decreased reaction rate of resvera-
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