M. Boccellino et al. / European Journal of Medicinal Chemistry 180 (2019) 637e647
643
the recent findings, where pterostilbene, exhibited promising
chemotherapeutic properties, may be due to the higher lip-
ophilicity of pterostilbene scaffold, which may result in better
permeability.
were carried out in 10 mL glass tubes, sealed with aluminium/
Teflon crimp tops, which can be exposed to 300 ꢀC and 30 bar in-
ternal pressure. After the irradiation period, the reaction vessel was
cooled rapidly (60e120s) to ambient temperature by gas jet cool-
ing. Flash chromatography was performed on Carlo Erba silica gel
60 (230e400 mesh; Carlo Erba, Milan, Italy). TLC was carried out
using plates coated with silica gel 60F 254 nm purchased from
Merck (Darmstadt, Germany). 1H and 13C NMR spectra were
registered on a Brucker AC 300. Chemical shifts are reported in
ppm. The abbreviations used are follows s, singlet; d, doublet; dd
double doublet; bs, broad signal. MS spectrometry analysis ESI-MS
was carried out on a Finnigan LCQDeca ion trap instrument.
2.7. Docking studies with 5-LO
All of the seven molecules were docked into the crystal structure
of human 5-LOX (PDB code: 3O8Y) [63]. After docking experiments,
the best and the most energetically favorable pose of each ligand
was selected. The protein-ligand complexes were analyzed to
identify the most conserved interactions. The most active mole-
cules compound 6 and compound 7 in the series (IC50 ¼ 0.07 and
0.05
mM, respectively) are able to make strong interactions through
4.1.1. General procedure for synthesis of compounds 3,4,5,6,7
The synthesis of piceatannol structural analogues was carried
out under microwave irradiation by Suzuky-coupling conditions.
To a solution of trans-2-(3,5-dimethoxyphenyl)-vinylboronic
acid pinacol ester (1.2 mmol) in EtOH abs. (2,5 mL), [1,10 bis(di-
phenylphosphino)ferrocene]dichloropalladium (II) (0.005 mmol),
K2CO3 anhydrous (2 mmol) and the corresponding brominated
compound (1 mmol) were added. The reaction mixture was stirred
and irradiated by microwave at 110 ꢀC for 30 min. Then the reaction
was filtered and concentrated under reduced pressure. The residue
was purified by flash chromatography on silica gel using hexane/
ethyl acetate (from 95:5 to 7:3) as eluent to give the corresponding
derivatives.
hydrogen bonding with the side chains of both His372 and His367
as well as filling the hydrophobic region with 3,5-dimethoxy
groups (Fig. 8F and G). Compounds 2, 3 and 4 with IC50 values in
the range of 0.24e0.76 mM are also positioned in the active site to
establish similar H-bonding interactions with these His residues
through their p-hydroxy or p-methoxy groups (Fig. 8B and C and D).
The docking poses of the least potent compound 1 and compound 5
indicates that these compounds are not oriented appropriately to
form these conserved H-bond interactions, which is in good
agreement with the observed activity loss (IC50 ¼ 4.9 and 5.48
mM,
respectively).
3. Conclusion
4.1.2. 4-(3,5-dimethoxystyryl)phenol (3)
Research and development of stilbene-based medicinal chem-
istry have become rapidly evolving with increasingly active com-
pounds covering almost the whole range of therapeutic fields.
The results of the present work indicated that piceatannol (2)
exerts a profound effect against hypoxia-induced injury for H9c2
cardiomyocytes through suppression of oxidative stress, while,
with a direct evaluation of early apoptotic cells, pterostilbene (3)
demonstrate suppressive effects on apoptosis. Moreover, picea-
tannol and synthetic pterostilbene derivatives showed significant
activity in inhibiting 5-LOX in both cell-based and cell-free assay,
with IC50 values in the low micromolar range. Additionally, the
results indicate that minimal differences in the structure of poly-
methoxystilbenes can substantially affect both the inhibitory 5-LOX
activity and the protection capability over cardiomyocyte injury. In
this context, we highlight fast chemical methodologies for the
synthesis of stilbene derivatives and outline the successful design
of novel stilbene based hybrids as antiinflammatory and antioxi-
dant compounds, that could be of interest in the development of
targeted pharmaceutical approaches for limiting ischemic damage.
This information may be useful in further design of stilbene-based
molecules as new leads for the development of novel agents with
clinical potential or as effective chemical probes. The results pre-
sented in this research cannot be generalized to animal models, but
our new lead stilbene derivatives appear to be highly suitable for a
posterior evaluation to dissect biological processes in the progres-
sion of myocardial tissue damage during ischemia. To this end,
further studies are in progress to confirm the possibility of using
these compounds in human therapies.
Yield: 43%. Rf: 0.4 in 8:2 hexane/ethyl acetate 1H NMR (CDCl3,
300 MHz):
d
: 7.42 (d, 2H); 6.99 (dd, 2H); 6.85 (d, 2H); 6.68 (s, 2H);
6.42 (t, 1H); 3.86 (s, 6H). 13C NMR (CDCl3, 300 MHz):
d
55.4, 99.7,
104.4, 115.7, 126.6, 128.0, 128.7, 130.1, 139.7, 155.4, 160.9 ESI(m/z):
256.3 [Mþ þ 1].
4.1.3. 1-(3,5-dimethoxystyryl)-4-methoxybenzene (4)
Yield: 46%. Rf: 0.4 in 9:1 hexane/ethyl acetate 1H NMR (CDCl3,
300 MHz):
d
: 7.47 (d, 2H); 6.99 (dd, 2H); 6.91 (d, 2H); 6.68 (s, 2H);
6.40 (t, 1H); 3.86 (s, 9H). 13C NMR (CDCl3, 300 MHz):
d
55.4, 99.6,
104.3, 114.1, 126.6, 127.8, 128.7, 129.9, 139.7, 159.4, 160.9 ESI(m/z):
271.6 [Mþ þ 1].
4.1.4. 5-(3,5-dimethoxystyryl)-2-methoxyphenol (5)
Yield: 44%. Rf: 0.6 in 6:4 hexane/ethyl acetate 1H NMR (CDCl3,
300 MHz):
d
: 7.42 (d, 2H); 6.99 (dd, 2H); 6.85 (d, 2H); 6.68 (s, 2H);
6.42 (t, 1H); 3.86 (s, 6H). 13C NMR (CDCl3, 300 MHz):
d
55.4, 56.0,
60.4, 99.7, 104.4, 110.6, 111.9, 119.4, 127.1, 128.8, 130.9, 139.6, 145.8,
146.5, 160.9 ESI(m/z): 309.3 [Mþ þ 23].
4.1.5. 4-(3,5-dimethoxystyryl)-2-methoxyphenol (6)
Yield: 42%. Rf: 0.7 in 7:3 hexane/ethyl acetate 1H NMR (CD3OD,
300 MHz):
d: 7.12 (s, 1H); 6.98 (d, 2H); 6.97 (dd, 2H); 6.79 (d, 2H);
6.36 (t, 1H); 3.89 (s, 3H); 3.79 (s, 3H). 13C NMR (CD3OD, 300 MHz):
d
55.4, 56.0, 60.4, 99.7, 104.4, 110.6, 111.9, 119.4, 127.1, 128.8, 130.9,
139.6, 145.8, 146.5, 160.9 ESI(m/z): 309.3 [Mþ þ 23].
4.1.6. 4-(3,5-dimethoxystyryl)benzene-1,2-diol (7)
Yield: 43%. Rf: 0.6 in 6:4 hexane/ethyl acetate 1H NMR (CD3OD,
4. Experimental section
300 MHz):
6,31 (d,2H); 6.56 (d,1H); 6.63 (s, 1H); 6, 76 (d, 1H); 6,88 (d, 2H). 13
NMR (CD3OD, 300 MHz): 55.9, 56.0, 101.4, 107.2, 114.1, 118.8, 121.7,
d: 3.74 (s, 3H); 3.77 (s, 3H); 5,21 (s,-OH); 6.16 (s, 1H);
C
4.1. Chemistry
d
128.8, 128.9, 131.0, 136.6, 147.1, 147.3, 161.3, 161.9 ESI(m/z): 272.3
All reagents were analytical grade and purchased from
SigmaeAldrich (Milano, Italy). All microwave irradiation experi-
ments were carried out in a Biotage® Initiator þ Microwave syn-
thesizer (Biotage, Sweden AB, Uppsala, Sweden). The reactions
[Mþ þ 23].
4.1.7. General procedure for synthesis of compounds 2
To a solution of 6 (1 mmol) in CH2Cl2 (4 mL), was added