Resveratrol Derivatives and Their Role as Potassium Channels Modulators

Article abstract of DOI:10.1021/np0303153

A series of stilbenoid analogues of resveratrol (trans-3,4′ ,5-trihydroxystilbene) with a stilbenic or a bibenzylic skeleton have been prepared by partial synthesis from resveratrol and dihydroresveratrol. The synthesized compounds have been evaluated for their ability to modulate voltage-gated channels.

Full text of DOI:10.1021/np0303153

J . Nat. Prod. 2004, 67, 421-426
421
Resver a tr ol Der iva tives a n d Th eir Role a s P ota ssiu m Ch a n n els Mod u la tor s
F. Orsini,*,† L. Verotta,† M. Lecchi,‡ R. Restano,‡ G. Curia,‡ E. Redaelli,‡ and E. Wanke‡
Dipartimento di Chimica Organica e Industriale, Universita` degli Studi di Milano, Via Venezian 21, Milano, Italy, and
Dipartimento di Biotecnologie e Bioscienze, Universita` di Milano-Bicocca, P.zza Della Scienza 2, Milano, Italy
Received J uly 17, 2003
A series of stilbenoid analogues of resveratrol (trans-3,4′,5-trihydroxystilbene) with a stilbenic or a
bibenzylic skeleton have been prepared by partial synthesis from resveratrol and dihydroresveratrol.
The synthesized compounds have been evaluated for their ability to modulate voltage-gated channels.
Stilbenes, produced by several plants in response to
pathogen attacks, regulate many biological functions. In
agreement with their role as phytoalexins, antifungal,
antibacterial, and cytotoxic activities have been reported.1
Some of them, such as resveratrol (trans-3,4′,5-trihy-
droxystilbene), exert antioxidant activity;2 modulate the
synthesis of lipids;3 inhibit ribonucleotide reductase4 and
DNA polymerase;5 increase the activity of Map-kinase,6 an
enzyme potentially related to neurodegenerative deseases
such as Alzheimer’s and Parkinson’s; inhibit platelet
aggregation7 and alter the eicosanoid synthesis,8 both
effects probably related to the inhibition of the cyclooxy-
genase and hydroperoxidase activities.9 These findings
have stimulated the study of these compounds as antiin-
flammatory, cardiotonic, and antiplatelet aggregating agents.
In addition, some stilbenoids (stilbenes and bibenzyls)
have shown properties more strictly related to cancer
chemoprevention and treatment, such as inhibition of
tubulin polymerization10 and antiestrogenic activity (spe-
cially useful for treatment of hormone-dependent can-
cers).11 Resveratrols have been found to inhibit the growth
of different types of tumors, such as histiocytic lymphoma,
prostate, colon, and breast cancers. They demonstrate this
effect through distinct processes, inducing the expression
of pro-apoptotic genes, inhibiting progression in the cell
cycle, modulating NO production, and interacting with
estrogen receptors.12 In general, they inhibit cellular events
associated with tumor initiation, promotion, and progres-
sion.9,12
F igu r e 1. Trans and cis derivatives of resveratrol.
Our interest in the field of polyhydroxylated phenols, in
particular stilbenoids, previously led to the isolation of the
2′-O-â-D-glucoside of combretastatin A-1 (3,4,4′,5-tetra-
methoxy-2′,3′-dihydroxystilbene) and of combretastatin B-1
(3,4,4′,5-tetramethoxy-2′,3′-dihydroxydihydrostilbene),10 the
3′-O-â-D-glucoside of resveratrol,7b and the total synthesis
of the natural compounds as well as of several analogues
that have been tested with respect to different biological
activities, evidencing interesting behaviors.7b,13 We ob-
served that some polyhydroxystilbenes selectively and
reversibly increase the duration of the action potential in
neural cells, by inhibiting the repolarization of potassium
channels,14 a kind of activity already found in other tissues
in connection with antitumor (tamoxifen) and cardiac
antiarythmic (tedisamil) agents. The diffusion of potassium
ions across cell membranes, through potassium channels,
underlines many fundamental biological processes.
On the basis of the preliminary results, we have under-
taken the synthesis of several resveratrol analogues, to
study the mechanism of their modulatory action of sodium
and two voltage-dependent potassium currents.
Resu lts a n d Discu ssion
The analogues shown in Figures 1 and 2 and in Scheme
1 have been synthesized either by partial or by total
synthesis, in the former case by modifying the structure
of the parent compound resveratrol (trans-3,4′,5-trihydroxy-
stilbene).
The structure of resveratrol has been modified with the
aim to vary (a) its lipophilicity in order to study the
selectivity toward cell walls and, as a consequence, toward
different tissues and (b) its geometry, with particular
reference to the distance and the mutual orientation of the
phenyl groups. The lipophilicity has been modified by the
introduction of lipophilic chains in different positions of the
molecule: several derivatives have been prepared that
differ in the number and the position of the free hydroxyl
groups and in the lipophilic chain used. The geometry of
* To whom correspondence should be addressed. Tel: +39 02 5031 4111.
Fax: +39 02 5031 4106. E-mail: fulvia.orsini@unimi.it.
† Universita` degli Studi di Milano.
‡ Universita` di Milano-Bicocca.
10.1021/np0303153 CCC: $27.50
© 2004 American Chemical Society and American Society of Pharmacognosy
Published on Web 02/20/2004

422 J ournal of Natural Products, 2004, Vol. 67, No. 3
Orsini et al.
the C-alkylated product at C4. The yields and the isomeric
ratios can be modulated by changing the experimental
conditions (reagent ratio, temperature, time), and the
isomers can be separated by flash chromatography. Start-
ing material was also recovered (5-25%) by flash chroma-
tography and recycled.
To test the influence of the stilbenic double-bond con-
figuration on the biological activity, the cis-derivative 7 was
also synthesized (Scheme 1). Since trans-cis isomerization
of the corresponding trans-isomer is not convenient, com-
pound 7 was synthesized by reaction between the phos-
phonium salt of the commercially available 4-methoxy-
benzyl chloride and 3,5-bis(tert-butyldimethylsilyloxy)-
benzaldehyde followed by desilylation with tetrabutylam-
monium fluoride, according to a reported protocol.13 A 2.3/1
mixture of trans- and cis-4′-O-methylresveratrol 1a and 7
(98% yield) was obtained and then divided in two portions.
One was submitted to crystallization and flash chroma-
tography, to give pure 1a and 7. The second portion was
hydrogenated, in the presence of palladium on charcoal,
to give the bibenzyl derivative 8a . In fact, we wanted to
test the influence of the double bond on activity and also
to verify whether bibenzyls could take advantage of their
greater conformational freedom and act as easier-to-
prepare mimetics of either the corresponding cis- or trans-
stilbenes, in case the only role of the double bond is to keep
the phenyl rings in a proper mutual orientation, without
a direct influence on activity. This assumption had been
already confirmed by a molecular modeling study per-
formed on trans- and cis-resveratrol as well as on dihy-
droresveratrol.15
Indeed, preliminary results obtained in the evaluation
of the influence on potassium channels evidenced a greater
activity of the bibenzyl 8a (Scheme 1 and Figure 2) with
respect to the corresponding trans-stilbene derivative 1a ,
whereas 8a and the cis-derivative 7 showed comparable
activity. These observations were conclusive and shifted
our attention to the derivatives with a bibenzyl skeleton.
Derivatives 8-13 were prepared from dihydroresveratrol
(obtained by hydrogenation of resveratrol in the presence
of palladium on charcoal) using benzyl, methyl, or 3,3-
dimethylallyl bromide in dimethylformamide, according to
the protocol optimized for the preparation of the derivatives
1-5 (Figure 2). Using 3,3-dimethylallyl bromide, the C4-
alkylated derivative 13 was also isolated, albeit in low
yields (15% yield). A different protocol, using aqueous
sodium hydroxide in dimethylformamide, was tested for the
F igu r e 2. Bibenzyl derivatives obtained by modification of dihy-
droresveratrol.
the molecule can be significantly affected by the configu-
ration (trans or cis) of the olefinic double bond. Reduction
to give bibenzyls (R,â-dihydrostilbenes) was also considered
to test whether the double bond is essential for activity or
not.
To test the influence (in terms of number and position)
of free phenolic groups on activity, the methyl derivatives
1a -5a (Figure 1) were first synthesized by direct treatment
of resveratrol with methyl iodide in dimethylformamide
(acetone can be used as well) in the presence of potassium
carbonate. This, among the proposed protocols, has been
chosen because it is very simple and easy to scale-up and
allows obtaining in one step all the isomers required for
the biological evaluation. The protocol was then extended
to the introduction of benzyl and dimethylallyl groups, the
latter being encountered in natural prenylated stilbenoids
as well as in other natural compounds where the prenyl
moiety has been further elaborated. In all cases the
O-alkylated products were generally obtained, except for
the reaction with 3,3-dimethylallyl bromide, which yielded
Sch em e 1. Total Synthesis of cis- and trans-4′-O-Methylresveratrol and 4′-O-Methyldihydroresveratrol

Resveratrol Derivatives
J ournal of Natural Products, 2004, Vol. 67, No. 3 423
Ta ble 1. Effects of trans-Resveratrol, Dihydroresveratrol, and Selected Analogues on Potassium Channels
compound
trans-resveratrol
final concentration (µM)
Ierg blocked %; n
IDR blocked %; n
trans-Resveratrol and Dihydroresveratrol
90
90
28.9; 7
39.2; 6
42.9; 6
52.0; 6
dihydroresveratrol
trans- and cis-Stilbene Analogues
3a (trans 3,4′-di-O-methyl-)
7 (cis 4′-O-methyl-)
30
90
11.5; 8
27.7; 9
9.5; 7
70.4; 6
Bibenzyl Analogues
8a (4′-O-methyl-)
8b (4′-O-benzyl-)
9a (3-O-methyl-)
9b (3-O-benzyl)
90
90
90
90
36
90
24.8; 8
18.0; 9
45.3; 7
68.0; 5
53.7; 6
41.2; 6
89.4; 6
89.0; 5
69.0; 7
89.0; 6
55.5; 7
77.2; 5
9ca (3-O-dimethylallyl-)
10a +11a (1.7/1 molar ratio)
(3,4′-di-O-methyl- and 3,5-di-O-methyl-)
10b (3,4′-di-O-benzyl-)
12a (3,4′,5-tri-O-methyl-)
12b (3,4′,5-tri-O-benzyl-)
13b (4-C-dimethylallyl-)
90
90
90
45
53.0; 5
11.3; 7
no effect; 8
50.1; 6
50.0; 6
38.6; 8
57.0; 6
74.0; 7
a
b
This compound was also tested at 90 µM on IERG with blockade of 88.7%. This compound was also tested at 90 µM on IERG with
blockade of 88.2%.
reaction with benzyl bromide and afforded, after flash
chromatography, 61% yield of the two bis-derivatives 10b
and 11b and a mixture of the two mono-derivatives 8b and
9b. The tribenzyl derivative 12b was not isolated.
methylresveratrol 3a and 3,4′-di-O-methyldihydroresvera-
trol 10a (the latter as a mixture with the corresponding
3,5-di-O-methyl derivative 11a ). Dihydroresveratrol, the
mono 3-O-alkylated derivatives 9a -c, and the 3,4′ dialky-
lated derivatives 10a ,b blocked both ERG and DR currents
quite strongly. Dihydroresveratrol blocked 39.2% ERG and
52% DR; compound 9a blocked 45.3% ERG and 69.0% DR.
The different intensity of blockage between ERG and DR
was more marked for some compounds, for example, the
cis-stilbene derivative 7 (27.7% ERG and 70.4% DR) and
the bibenzyl derivatives 8a (24.8% ERG and 89.4% DR).
The compounds 7 and 8a blocked sodium current very
strongly (data not shown). The obtained results would
suggest that mono-O-alkylation of the phenolic function at
C-4′ in dihydroresveratrol enhances inhibitory activity on
the IDR current and depresses activity on the IERG current,
whereas mono-O-alkylation of the phenolic function at C-3
and mono-C-alkylation at C-4 enhance activity on both IERG
and IDR currents. Tri-O-alkylation depressed inhibitory
The effects of some resveratrol derivatives were tested
on the F-11 neuroblastoma cell line, which expresses a
sodium current (INa) and two different types of voltage-
dependent potassium currents: a rapidly inactivating
inward-rectifying current (IERG) and a slowly inactivating
delayed rectifier current (IDR).16 As is well known, sodium
channels promote the action potential upstroke in excitable
cells; on the contrary, delayed rectifier (DR) potassium
channels counteract the role of sodium channels, inducing
action potential repolarization.17 The ERG channel, en-
coded by the human ether-a`-go-go-related gene, belongs to
a family of voltage-activated, outward-rectifying potassium
channels. Gene mutations that cause an inherited cardiac
disorder known as long QT syndrome (LQT) pointed out
ERG channels function in repolarization of cardiac action
potential.18 Studies made in other tissues, such as nervous
system, pituitary gland, and pancreas, revealed ERG
implications also in neuronal excitability and in modulation
of hormone release.19 In addition, it has been suggested
that ERG channels have a role in supporting neoplastic
cell proliferation.20 ERG channels are present in tumor cells
of various histogenesis, where they establish a depolarized
resting potential which is required for cell proliferation.20
Also other potassium channels, different from ERG, seem
to play an important role in tumor cell proliferation, and
sodium channels were demonstrated to be able to enhance
the metastatic potential of rat cancer prostate cells.21
To record currents flowing through potassium channels,
we performed experiments by patch clamp technique in the
whole-cell configuration. We tested resveratrol, dihydrores-
veratrol, and compounds from the three groups of resvera-
trol derivatives: trans- and cis-stilbene derivatives and
bibenzyl derivatives. The data are summarized in Table
1.
activity on IERG
.
Our data suggest that, despite their lack of target
specificity among ion channels, resveratrol derivatives
modulate voltage-gated potassium channels similarly to the
parent compound, and in some cases they show better
activity and higher specificity toward IDR than IERG cur-
rents.
Recently, resveratrol has been found to directly stimulate
large-conductance Ca2+-activated potassium channel activ-
ity in vascular endothelial cells. These channels are
believed to play an important role in controlling hormonal
secretion in neurons or neuroendocrine cells.22
In view of recent findings, the action of resveratrol and
its derivatives on ion channels, although not exhaustive,
offers opportunities for discovering novel therapeutic agents
as well as significant challenges in the form of tissue and
organ specificity.
Exp er im en ta l Section
All compounds affected potassium currents, revealing a
low specificity of blockage. All compounds had less effect
on ERG current than on the DR one; only derivatives 3a
and 10b did not follow this pattern. Reduction of the
stilbenic double bond in resveratrol to give dihydroresvera-
Gen er a l Exp er im en ta l P r oced u r es. Resveratrol was
donated by Pharmascience Inc. (Montreal, Canada). Reagent
grade tetrahydrofuran was refluxed over LiAlH4 and distilled.
Reagent grade dimethylformamide was distilled at reduced
pressure under nitrogen and kept over 4 Å molecular sieves.
(E)-4′-O-Methylresveratrol,13 (Z)-4′-O-methylresveratrol,13
and dihydroresveratrol13,23 have been synthesized according
to the reported protocols.
trol enhanced inhibitory activity on both IERG and IDR
.
Activity enhancement following reduction of the double
bond was confirmed by the comparison between 3,4′-di-O-

424 J ournal of Natural Products, 2004, Vol. 67, No. 3
Orsini et al.
1H NMR and 13C NMR spectra were recorded at 200 and
300 MHz on Bruker spectrometers. MS spectra were recorded
with a VG7070 E9 spectrometer. Melting points were obtained
by using a Buchi 535 apparatus. Flash-column chromatogra-
phies were performed on silica gel Merck Kieselgel 60 (230-
400 mesh). Thin-layer chromatographies were performed on
silica gel plates (60 F254, Merck); spots were detected visually
by ultraviolet irradiation (254 nm) or by spraying with
methanol/H2SO4, 9:1, followed by heating at 100 °C.
Typ ica l P r oced u r e for th e P r ep a r a tion of Com p ou n d s
1-13. Dry potassium carbonate (0.68 g, 4.92 mmol) was added
to a solution of resveratrol (0.56 g, 2.46 mmol) in dry dimeth-
ylformamide (8 mL). Methyl iodide (0.23 mL, 3.68 mmol) was
added dropwise. The reaction was monitored by TLC (silica
gel, eluting with n-hexane/ethyl acetate, 7:3). After 6 h, the
reaction mixture was filtered. The filtrate was diluted with
water (6 mL) and extracted with ethyl acetate (3 × 15 mL).
The combined organic extracts were dried (Na2SO4), and the
solvent was removed under reduced pressure. The crude
material was flash chromatographed (silica gel, eluting with
n-hexane/ethyl acetate, 7:3) and afforded 3,4′,5-tri-O-methyl-
resveratrol 5a (37%), 3,4′-di-O-methylresveratrol 3a (10%), 3,5-
di-O-methylresveratrol 4a (20%), 4′-O-methylresveratrol 1a 13
(10%), and starting resveratrol (10%). 3-O-Methylresveratrol
was obtained in traces.
(1H, dd, J ) 1.8, 1.8 Hz, H-4), 6.60 (2H, d, J ) 8.4 Hz, H-3′
and H-5′), 6.75 (2H, d, J ) 1.8 Hz, H-2 and H-6), 6.93 and
7.04 (2H, AB system, J ) 15.0 Hz, CHdCH), 7.6-7.2 (15H,
m), 7.10 (2H, d, J ) 8.4 Hz, H-2′ and H-6′), 7.2-7.6 (15 H);
EIMS m/z 498 [M+]; anal. C 84.16%, H 5.94%, calcd for
C
35H30O3 C 84.34%, H 6.02%.
1c: colorless syrup; H NMR (CDCl3 + D2O) δ 1.75 (3H, s,
1
CH3), 1.85 (3H, s, CH3), 4.50 (2H, m, CH2), 5.5 (1H, dd, J )
7.0, 7.0 Hz, CHdC), 6.20 (1H, s, H-4), 6.58 (2H, s, H-2 and
H-6), 6.80 (2H, d, J ) 8.3 Hz, H-3′ and H-5′), 6.90 and 7.05
(2H, AB system, J ) 15.7 Hz, CHdCH), 7.10 (2H, d, J ) 8.3
Hz. H-2′ and H-6′); EIMS m/z 296 [M+]; anal. C 77.35%, H
6.80%, calcd for C19H20O3, C 77.03%, H 6.70%.
1
2c: colorless syrup; H NMR (CDCl3 + D2O) δ 1.75 (3H, s,
CH3), 1.85 (3H, s, CH3), 4.5 (2H, m, CH2CH2), 5.5 (1H, dd, J )
7.0, 7.0 Hz), 6.32 (1H, s, H-4), 6.58 (1H, s, H-6), 6.65 (1H, s,
H-2), 6.82 and 6.98 (2H, AB system, J ) 15.8 Hz, CHdCH),
6.90 (2H, d, J ) 8.0 Hz, H-3′ and H-5′), 7.11 (2H, d, J ) 8.0
Hz, H-2′ and H-6′); EIMS m/z 296 [M+]; anal. C 77.38%, H
6.58%, calcd for C19H20O3 C 77.03%, H 6.70%.
1
3c: colorless syrup; H NMR (CDCl3 + D2O) δ 1.71 (6H, s,
2 × CH3), 1.82 (6H, s, 2 × CH3), 4.50 (2H, d, J ) 6.8 Hz, CH2),
4.53 (2H, d, J ) 6.8 Hz, CH2), 5.5 (2H, dd, J ) 6.8, 6.8 Hz,
CHdC), 5.51 (2H, dd, J ) 6.8, 6.8 Hz, CHdC), 6.32 (1H, dd, J
) 1.8, 1.8 Hz, H-4), 6.58 (1H, d, J ) 1.8 Hz, H-6), 6.65 (1H, d,
J ) 1.8 Hz, H-2), 6.84 and 6.98 (2H, AB system, J ) 15.8 Hz,
CHdCH), 6.90 (2H, d, J ) 8.0 Hz, H-3′ and H-5′), 7.11(2H, d,
J ) 8.0 Hz, H-2′ and H-6′); EIMS m/z 364 [M+], 107, 69; anal.
C 79.48%, H 7.58%, calcd for C24H28O3, C 79.12%, H 7.69%.
5c: colorless syrup; 1H NMR (CDCl3) δ 1.78 (6H, s, 2 × CH3),
1.88 (12H, s, 3 × CH3), 4.48 (2H, d, J ) 6.9 Hz, CH2), 4.51
(4H, d, J ) 6.9 Hz, CH2), 5.5 (3H, t, J ) 6.9, 6.9 Hz, CHdC),
6.41(1H, dd, J ) 2.0, 2.0 Hz, H-4), 6.88 and 7.01 (2H, AB
system, J ) 16.0 Hz, CHdCH), 6.89 (2H, d, J ) 2.0 Hz, H-2
and H-6), 6.89 (2H, d, J ) 8.0 Hz, H-3′ and H-5′), 7.01 (2H, d,
J ) 8.0 Hz, H-2′ and H-6′); EIMS m/z 432 [M+], 107, 69.
6: colorless syrup; 1H NMR (CDCl3) δ 1.75 (3H, s, CH3),
1.85 (3H, s, CH3), 3.38 (2H, d, J ) 6.9 Hz, CH2), 5.5 (1H, d, J
) 6.9 Hz, CHdC), 6.7 (2H, s, H-2 and H-6), 6.95 (2H, d, J )
8.4 Hz, H-3′ and H-5′), 6.95 and 7.05 (2H, AB system, J )
15.8 Hz, CHdCH), 7.48 (2H, d, J ) 8.4 Hz, H-2′ and H-6′);
EIMS m/z 296 [M+]; anal. C 77.38%, H 6.58%, calcd for
1a :13 colorless crystals (EtOAc/n-hexane); mp 176-178 °C;
1H NMR (CDCl3 + D2O) δ 3.79 (3H, s, CH3 ), 6.15 (1H, dd, J
) 2.0, 2.0 Hz, H-4), 6.45 (2H, d, J ) 2.0 Hz, H-2 and H-6),
6.90 and 7.01 (2H, AB system, J ) 16.4 Hz, CHdCH), 6.93
(2H, d, J ) 8.6 Hz, H-3′ and H-5′), 7.51 (2H, d, J ) 8.6 Hz,
H-2′ and H-6′); EIMS m/z 242 [M+], 121 [C8H9O].
3a : colorless crystals (EtOAc/n-hexane); mp 115-117 °C; 1H
NMR (CDCl3 + D2O) δ 3.85 (3H, s, CH3), 3.89 (3H, s, CH3),
6.31 (1H, dd, J ) 2.3, 2.3 Hz, H-4), 6.57 (1H, d, J ) 2.3 Hz,
H-2), 6.63 (1H, d, J ) 2.3 Hz, H-6), 6.89 and 7.05 (2H, AB
system, J ) 15.8 Hz, CHdCH), 6.95 (1H, d, J ) 8.8 Hz, H-3′
and H-5′), 7.45 (2H, d, J ) 8.8 Hz, H-2′ and H-6′); EIMS m/z
256 [M+]; 121 [ C8H9O]; anal. C 74.58%, H 6.18%, calcd for
C
16H16O3, C 75%, H 6.25%.
4a :23 colorless syrup; 1H NMR (CDCl3 + D2O) δ 3.85 (6H, s,
CH3), 6.4 (1H, dd, J ) 2.0, 2.0 Hz, H-4), 6.7 (2H, d, J ) 2.0
Hz, H-2 and H-6), 6.90 and 7.00 (2H, AB system, J ) 15.8 Hz,
CHdCH), 6.91 (1H, d, J ) 8.8 Hz, H-3′ and H-5′), 7.45 (2H, d,
J ) 8.8 Hz, H-2′ and H-6′); EIMS m/z 256 [M+], 121 [C8H9O].
5a :23 colorless crystals (EtOAc/n-hexane); mp 57 °C; 1H NMR
(CDCl3);23 EIMS m/z 270 [M+], 121 [C8H9O].
C
19H20O3, C 77.03%, H 6.76%.
8a : colorless crystals (EtOAc/n-hexane); mp 61 °C; 1H NMR-
(DMSO-d6 + D2O) δ 2.68 (4H, m, CH2CH2), 3.67 (3H, s, CH3),
6.03 (1H, dd, J ) 2.0, 2.0 Hz, H-4), 6.08 (2H, d, J ) 2.0 Hz,
H-2 and H-6), 6.85 (2H, d, J ) 8.0 Hz, H-3′ and H-5′), 7.15
(2H, d, J ) 8.0 Hz, H-2′ and H-6′); EIMS m/z 244 [M+], 123,
121; anal. C 61.30%, H 6.66%, calcd for C15H16O3, C 61.48%,
H 6.56%.
1b: colorless crystals (EtOAc/n-hexane); mp 114-117 °C;
1H NMR (CDCl3 + D2O) δ 5.18 (2H, s, CH2), 6.25 (1H, dd, J )
2.2, 2.2 Hz, H-4), 6.58 (2H, d, J ) 2.2 Hz, H-2 and H-6), 6.83
(2H, d, J ) 8.3 Hz, H-3′ and H-5′), 6.90 and 7.05 (2H, AB
system, J ) 15.0 Hz, CHdCH), 7.08 (2H, d, J ) 8.3 Hz, H-2′
and 6′), 7.5-7.2 (5H, m); EIMS m/z 318 [M+]; anal. C 78.99%,
H 5.64%, calcd for C21H18O3, C 79.25%, H 5.66%.
9a : colorless syrup; 1H NMR (DMSO-d6) δ 2.7 (4H, m, CH2-
CH2), 3.65 (3H, s, CH3), 6.12 (1H, dd, J ) 2.0, 2.0 Hz, H-4),
6.2 (2H, d, J ) 2.0 Hz, H-2 and H-6), 6.64 (2H, d, J ) 8.5 Hz,
H-3′ and H-5′), 6.99 (2H, d, J ) 8.5 Hz, H-2′ and H-6′), 9.1
(1H, bs, OH, exchanges with D2O), 9.2 (2H, bs, 2 × OH,
exchanges with D2O); EIMS m/z 244 [M+], 123, 121; anal. C
61.32%, H 6.60%, calcd for C15H16O3, C 61.48%, H 6.56%.
1
2b: colorless syrup; H NMR (CDCl3 + D2O) δ 5.18 (2H, s,
CH2), 6.25 (1H, dd, J ) 2.0, 2.0 Hz, H-4), 6.55 (1H, d, J ) 2.0
Hz, H-2), 6.7 (1H, d, J ) 2.0 Hz, H-6), 6.90 and 7.08 (2H, AB
system, J ) 15.4 Hz, CHdCH), 6.9 (1H, d, J ) 8.2 Hz, H-3′
and H-5′), 7.45 (1H, d, J ) 8.2 Hz, H-2′ and H-6′), 7.5-7.2
(5H, m); EIMS m/z 318 [M+].
1
10a : colorless syrup; H NMR (CDCl3 + D2O) δ 2.80 (4H,
m, CH2CH2), 3.21 (3H, s, CH3), 3.28 (3H, s, CH3), 6.23 (2H, s,
H-2 and H-6), 6.28 (1H, s, H-4), 6.82 (2H, d, J ) 8.5 Hz, H-3′
and H-5′), 7.08 (2H, d, J ) 8.5 Hz, H-2′ and H-6′); EIMS m/z
258 [M+]; anal. C 74.58%, H 6.68%, calcd for C16H18O3, C
74.42%, H 6.98%.
1
3b: colorless syrup; H NMR (CDCl3 + D2O) δ 5.09 (2H, s,
CH2), 5.18 (2H, s, CH2), 6.25 (1H, dd, J ) 1.5, 1.5 Hz, H-4),
6.55 (1H, d, J ) 1.5 Hz, H-2), 6.7 (1H, d, J ) 1.5 Hz, H-6), 6.8
(2H, d, J ) 8.3 Hz, H-3′ and H-5′), 6.9 and 7.08 (2H, AB system,
J ) 15.4 Hz, CHdCH), 7.1 (2H, d, J ) 8.3 Hz, H-2′ and H-6′),
7.5-7.2 (10H, m); EIMS m/z 408 [M+]; anal. C 82.55%, H
5.80%, calcd for C28H24O3 C 82.35%, H 5.88%.
11a : colorless syrup; 1H NMR (CDCl3 + D2O) δ 2.8 (4H, m,
CH2CH2), 3.75 (3H, s, CH3), 3.76 (3H, s, CH3), 6.33 (2H, s, H-2
and H-6), 6.34 (1H, s, H-4), 6.73 (2H, d, J ) 8.0 Hz, H-3′ and
H-5′), 7.34 (2H, d, J ) 8.0 Hz, H-2′ and H-6′); EIMS m/z 258
[M]+; anal. C 74.58%, H 6.68%, calcd for C16H18O3, C 74.42%,
H 6.98%.
4b: colorless crystals (EtOAc/n-hexane); mp 123-127 °C;
1H NMR (CDCl3 + D2O) δ 5.09 (2H, s, CH2), 5.11 (2H, s, CH2),
6.22 (1H, dd, J ) 1.5, 1.5 Hz, H-4), 6.55 (2H, d, J ) 1.5 Hz,
H-2 and H-6), 6.87 and 7.08 (2H, AB system J ) 15.0 Hz, CHd
CH), 6.76 (2H, d, J ) 8.3 Hz, H-3′ and H-5′), 7.05 (2H, d, J )
8.3 Hz, H-2′ and H-6′), 7.5 (10H, m); EIMS m/z 408 [M+]; anal.
C 82.10%, H 5.84%, calcd for C28H24O3, C 82.35%, H 5.88%.
5b: colorless crystals (EtOAc/n-hexane); mp 161 °C; 1H
NMR (CDCl3) δ 5.08 (4H, s, 2 × CH2), 5.10 (2H, s, CH2), 6.45
12a : colorless crystals (EtOAc/n-hexane); mp 61-63 °C; 1H
NMR (CDCl3) δ 2.87 (4H, m, CH2CH2), 3.8 (6H, s, 2 × CH3),
3.91 (3H, s, CH3), 6.34-6-37 (3H, H-2, H-4, H-6), 6.85 (2H,
d, J ) 8.3 Hz, H-3′ and H-5′), 7.11 (2H, d, J ) 8.3 Hz, H-2′
and H-6′); EIMS m/z 272 [M+], 151, 121; anal. C 75.23%, H
7.2%, calcd for C17H20O3, C 75.0%, H 7.35%.

Resveratrol Derivatives
J ournal of Natural Products, 2004, Vol. 67, No. 3 425
8b: colorless syrup; 1H NMR (CDCl3 + D2O) δ 2.87 (4H, bs,
CH2CH2), 5.0 (2H, s, CH2), 6.19 (1H, dd, J ) 2.0, 2.0 Hz, H-4),
6.24 (2H, d, J ) 2.0 Hz, H-2 and H-6), 6.90 (2H, d, J ) 8.5 Hz,
H-3′ and H-5′), 7.09 (2H, d, J ) 8.5 Hz, H-2′ and H-6′), 7.35-
7.45 (5H, m); EIMS m/z 320 [M+]; anal. C 78.58%, H 7.58%,
calcd for C21H20O3, C 78.75%, H 7.94%.
selective blocker of erg current, was kept as a 1 mM stock
solution in distilled water and applied at a final concentration
of 1 µM.
Resveratrol derivatives were prepared from 300 mM stock
solutions in DMSO. In the final solution DMSO was present
in the ratio of 1:2000, and it did not affect the currents. For
the final concentration of the single compounds, see Table 1.
9b: colorless syrup; 1H NMR (CDCl3 + D2O) δ 2.79 (4H, bs,
CH2CH2), 5.0 (2H, s, CH2), 6.24 (1H, d, J ) 2.3 Hz, H-2), 6.34
(1H, dd, J ) 2.3, 2.3 Hz, H-4), 6.41 (1H, d, J ) 8.5 Hz, H-3′
and H-5′), 6.42 (1H, d, J ) 2.3 Hz, H-2), 7.01 (2H, d, J ) 8.0
Hz, H-2′ and H-6′), 7.35-7.5 (5H, m); EIMS m/z 320[M+]; anal.
C 78.35%, H 7.90%, calcd for C21H20O3, C 78.75%, H 7.94%.
Cells plated on dishes were incubated at 37 °C for about 24
h. Patch clamp experiments were performed at room temper-
ature with an amplifier MultiClamp 700A (Axon Instruments,
CA) and 1200 Digidata (Axon Instruments, CA). The whole
cell configuration of the patch clamp technique was employed
using pipets (borosilicate glass; Clark Instruments UK) whose
resistance was in the range 2-4 MΩ. Extracellular solutions
were delivered through a 9-hole (0.6 mm) remote-controlled
linear perfusion manifold placed near the cell under study.
Cell capacitance and series resistance were compensated
(85-95%) before each protocol run. IDR were recorded using a
depolarizing stimulation at 60 mV from a holding potential of
-60 mV; for IDR the cells were perfused with a physiologic low
potassium solution. DR traces were TEA-isolated (data not
shown). ERG tail currents were elicited at a voltage of -120
mV after 15 s preconditioning at 0 mV; ERG traces were
recorded using an external high potassium solution and were
WAY 123.398-isolated (data not shown). For data acquisition
and analysis, pClamp 8 software (Axon Instruments, CA) and
Origin 6 (Microcal Software, Northampton, MA) were routinely
used.
1
10b: colorless syrup; H NMR (CDCl3 + D2O) δ 2.85 (4H,
s, CH2CH2), 5.02 (2H, s, CH2), 5.05 (2H, s, CH2), 6.29 (1H, d,
J ) 2.3 Hz, H-6), 6.35 (1H, dd, J ) 2.3, 2.3 Hz, H-4), 6.45 (1H,
d, J ) 2.3 Hz, H-2), 6.93 (2H, d, J ) 8.0 Hz, H-3′ and H-5′),
7.12 (2H, d, J ) 8.0 Hz, H-2′ and H-6′), 7.35-7.5 (10H, m);
EIMS m/z 410 [M+], 197; anal. C 81.58%, H 6.18%, calcd for
C
28H26O3, C 81.95%, H 6.34%.
11b: colorless syrup; H NMR (CDCl3) δ 2.85 (4H, s, CH2-
1
CH2), 5.02 (2H, s, CH2), 5.05 (2H, s, CH2), 6.45 (2H, d, J ) 2.2
Hz, H-2 and H-6), 6.5 (1H, dd, J ) 2.2, 2.2 Hz, H-4), 6.76 (2H,
d, J ) 8.4 Hz, H-3′ and H-5′), 7.05 (2H, d, J ) 8.4 Hz, H-2′
and H-6′), 7.35-7.5 (10H, m); EI MS m/z 410 [M+], 197; anal.
C 81.55%, H 6.20%, calcd for C28H26O3, C 81.95%, H 6.34%.
12b: colorless crystals (EtOAc/n-hexane); mp 81-83 °C; 1H
NMR (CDCl3 + D2O) δ 2.85 (4H, s, CH2CH2), 5.0 (4H, s, 2 ×
CH2), 5.4 (2H, s, CH2), 6.43 (2H, d, J ) 2.2 Hz, H-2 and H-6),
6.46 (1H, dd, J ) 2.2, 2.2 Hz, H-4), 6.9 (2H, d, J ) 8.4 Hz,
H-3′ and H-5′), 7.07 (2H, d, J ) 8.4 Hz, H-2′ and H-6′), 7.35-
7.5 (15H, m); EIMS m/z 500 [M+], 303, 197; anal. C 83.97%,
H 6.38%, calcd for C35H32O3, C 84.0%, H 6.4%.
Ack n ow led gm en t. Universita` degli Studi di Milano and
MIUR (Ministero dell’Istruzione, dell’Universita` e della Ricer-
ca) are acknowledged for financial support. (Cofin: Project code
2001037329-006). Pharmascience Inc. (Montreal, Quebec,
Canada) is acknowledged for a generous supply of resveratrol.
Dr. M. Ferrari is acknowledged for computer-aided biblio-
graphic research.
1
8c: colorless syrup; H NMR (CDCl3): δ 1.79 (3H, s, CH3),
1.81 (3H, s, CH3), 2.78 (2H, s, disappears with D2O), 2.86 (4H,
s, CH2CH2), 4.5 (2H, d, J ) 7.0 Hz), 5.0 (1H, dd, J ) 7.0, 7.0
Hz), 6.12 (1H, dd, J ) 2.0, 2.0 Hz, H-4), 6.15 (2H, d, J ) 2.0
Hz, H-2 and H-6), 6.7 (2H, d, J ) 8.1 Hz, H-3′ and H-5′), 7.0
(2H, d, J ) 8.1 Hz, H-2′ and H-6′); EIMS m/z 298 [M+], 107,
69; anal. C 76.28%, H 7.18%, calcd for C19H22O3, C 76.51%, H
7.38%.
Refer en ces a n d Notes
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9c: colorless syrup; 1H NMR (CDCl3) δ 1,79 (3H, s), 1.8 (3H,
s, CH3), 2.80 (4H, m, CH2CH2), 4.5 (2H, d, J ) 7.3 Hz, CH2),
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76.58%, H 7.38%, calcd for C19H22O3, C 76.51%, H 7.38%.
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13: colorless syrup; H NMR (CDCl3) δ 1.83 (6H, s, CH3),
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2.80 (4H, m, CH2CH2), 3.31 (2H, d, J ) 7.4 Hz, CH2), 5.10 (1H,
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a standard extracellular
solution containing (mM) NaCl 130, KCl 5, CaCl2 2, MgCl2 2,
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NP0303153