10.1002/ejoc.201701500
European Journal of Organic Chemistry
COMMUNICATION
However, the intrinsic binding constant is 10x higher than that
described for doxorubicin (Kb = 3.2 (±0.23) × 104 M-1).[16]
The binding of compound 4 to CT-DNA as a competitive
intercalative binding probe with GelRed[17] was further
analyzed. In the competitive binding experiments, GelRed was
first incubated with CT-DNA for 30 min to ensure sufficient
binding sites between GelRed and DNA (concentration ratio
was set at [GelRed]/[CT-DNA] = 1:10). The emission spectra
of GelRed–CT-DNA system in the absence and presence of
increasing concentrations of compound 4 are shown in Figure
3. As expected, when excited at 350 nm, the GelRed–CT-DNA
system presented a characteristic fluorescence emission at
around 590 nm, indicating intercalation of GelRed within the
Keywords: imidazolium salt • anthracenecarboxaldehyde •
arylidene anthrone • decarbonylation • DNA intercalation
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4
considerably quenched the GelRed’s fluorescence emission
(Figure 3 – indicated by the black arrow) with no observed
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Here we report for the first time an unusual hetero
arylidene-9(10H)-anthrone salt (4). Its structure was
unequivocally attributed by X-ray crystallography. A detailed
mechanistic study was carried out to provide insights to the
unexpected reactivity of the imidazolium salt and its oxidative
role. Alongside decarbonylation and the involvement of
endoperoxide species are proposed in the pathway for the
formation of the anthrone derivative 4. Compound 4 showed
no cytotoxicity in human normal healthy fibroblasts or in two
different cancer cell models, indicating it might be suitable for
several applications in biological systems. Compound 4
strongly interacts with CT-DNA by intercalation (Kb = 2.0(±
0.20) x 105 M-1), and is able to displace GelRed from the DNA
strands, thus quenching fluorescence of GelRed-CT-DNA
system (KSV=3.3 ±0.3 x 103 M-1).
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Acknowledgements
This work was supported by the LAQV, which is financed by
national funds from FCT/MEC(UID/QUI/50006/2013) and co-
financed by the ERDF under the PT2020 Partnership
Agreement (POCI-01-0145- 710-FEDER-007265), and by
UCIBIO
by
national
funds
from
FCT/MEC
(UID/Multi/04378/2013) and co-financed by the ERDF under
the PT2020 Partnership Agreement (POCI-01-0145-FEDER-
007728). The National NMR Facility and the SCXRD facility are
supported by Fundação para
a Ciência e Tecnologia
(RECI/BBB-BQB/0230/2012 and RECI/BBB-BEP/0124/2012,
respectively). We thank Dr. R. Pandian for the crystallographic
data collection. We acknowledge the Laboratório de Análises
REQUIMTE for the technical support for the mass
spectrometry analyses.
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