Antiviral activity and metal ion-binding properties of some 2-hydroxy-3-methoxyphenyl acylhydrazones

Article abstract of DOI:10.1007/s10534-017-0070-6

Here we report on the results obtained from an antiviral screening, including herpes simplex virus, vaccinia virus, vesicular stomatitis virus, Coxsackie B4 virus or respiratory syncytial virus, parainfluenza-3 virus, reovirus-1 and Punta Toro virus, of t

Full text of DOI:10.1007/s10534-017-0070-6

Biometals
https://doi.org/10.1007/s10534-017-0070-6
Antiviral activity and metal ion-binding properties of some
2-hydroxy-3-methoxyphenyl acylhydrazones
.
.
.
.
M. Carcelli
E. Fisicaro C. Compari L. Contardi
.
.
.
D. Rogolino C. Solinas A. Stevaert L. Naesens
Received: 21 November 2017 / Accepted: 24 November 2017
Springer Science+Business Media, LLC, part of Springer Nature 2017
©
Abstract Here we report on the results obtained
from an antiviral screening, including herpes simplex
virus, vaccinia virus, vesicular stomatitis virus,
Coxsackie B4 virus or respiratory syncytial virus,
parainfluenza-3 virus, reovirus-1 and Punta Toro
virus, of three 2-hydroxy-3-methoxyphenyl acylhy-
drazone compounds in three cell lines (i.e. human
embryonic lung fibroblast cells, human cervix carci-
noma cells, and African Green monkey kidney cells).
Interesting antiviral EC50 values are obtained against
herpes simplex virus-1 and vaccinia virus. The
biological activity of acylhydrazones is often attrib-
uted to their metal coordinating abilities, so
potentiometric and microcalorimetric studies are here
discussed to unravel the behavior of the three
2-hydroxy-3-methoxyphenyl compounds in solution.
It is worth of note that the acylhydrazone with the
higher affinity for Cu(II) ions shows the best antiviral
activity against herpes simplex and vaccinia virus
(EC50 ~ 1.5 µM, minimal cytotoxic concentra-
tion = 60 µM, selectivity index = 40).
Electronic supplementary material The online
version of this article (https://doi.org/10.1007/
s10534-017-0070-6) contains supplementary material,
which is available to authorized users.
Keywords Copper complex · Copper homeostasis ·
Antiviral · Acylhydrazone · Isothermal titration
calorimetry
M. Carcelli (&) · D. Rogolino
Department of Chemistry, Life Sciences and
Environmental Sustainability and CIRCMSB (Consorzio
Interuniversitario di Ricerca in Chimica dei Metalli nei
Sistemi Biologici) Parma Unit, University of Parma,
Parco Area delle Scienze 17/A, 43124 Parma, Italy
e-mail: mauro.carcelli@unipr.it
Introduction
Acylhydrazones are a class of compounds receiving
continuous attention in coordination and medicinal
chemistry. Even if this is partially due to the often
relatively simple synthetic strategies that are used to
obtain these compounds, their coordination abilities
still hold some interesting surprises (Jiang et al. 2015;
Vantomme and Lehn 2013). Recently, metal binding
agents were re-discovered as an important tool in
bioinorganic chemistry or as drugs to target transition
metal ion homeostasis (Chana et al. 2017; Helsel and
Franz 2015; Weekley and He 2017). In this context,
the N-acylhydrazone moiety represents a “privileged
E. Fisicaro · C. Compari · L. Contardi
Food and Drug Department, University of Parma, Parco
Area delle Scienze 27/A, 43124 Parma, Italy
C. Solinas
Chemistry and Pharmacy Department, University of
Sassari, Via Vienna 2, 07100 Sassari, Italy
A. Stevaert · L. Naesens
Rega Institute for Medical Research, KU Leuven –
University of Leuven, 3000 Louvain, Belgium
123

Biometals
structure”, because of its ability to provide, around a
common platform, ligands with different electronic
and steric characters. Recently, salicyl-hydrazone
analogues have been synthesized and evaluated for
their in vitro cytotoxic activities in some human
cancer cell lines (Sayed et al. 2017), as well as for
antiviral activity (Kim et al. 2016). In the last years,
also in our laboratory, studies have been undertaken
to assess the antiviral activity of hydroxy-phenyl
acylhydrazones (Carcelli et al. 2016; Rogolino et al.
Experimental
Materials and methods
All reagents of commercial quality were used without
further purification. The purity of the synthesized
compounds was determined by elemental analysis
and verified to be ≥ 95%. NMR spectra were
recorded at 25 °C on a Bruker Avance 400 FT
spectrophotometer. The attenuate total reflectance IR
spectra were recorded by means of a Nicolet-Nexus
(Thermo Fisher) spectrophotometer by using a dia-
2
015); particular attention was devoted to correlate
these biological activities with their coordinating
abilities. As a follow-up on this work, we here discuss
the coordinating behavior of three 2-hydroxy-3-
−1
mond crystal plate in the range of 4000–400 cm .
Elemental analyses were performed by using a
FlashEA 1112 series CHNS/O analyzer (Thermo
Fisher) with gas-chromatographic separation. Elec-
trospray mass spectral analyses (ESI-MS) were
performed with an electrospray ionization time-of-
flight Micromass 4LCZ spectrometer. MS spectra
were acquired in positive EI mode by means of a
direct exposure probe mounting on the tip of a Re-
filament with a DSQII Thermo Fisher apparatus,
equipped with a single quadrupole analyzer.
1
2
methoxyphenyl acylhydrazones HL , HL , and
3
H L (Scheme 1, R = C H , C H and C H OH)
2
6
5
7
15
6 4
towards some metal ions (Cu(II), Mn(II), Mg(II)),
that are essential in living systems. The R group is
choose to diversify the lipophilicity and the coordi-
nating ability of the three compounds. Moreover, here
1
2
we present the results of the evaluation of HL , HL ,
3
and H L in cell cultures infected with diverse DNA
2
or RNA viruses (i.e. herpes simplex virus, vaccinia
virus, vesicular stomatitis virus, Coxsackie B4 virus
or respiratory syncytial virus, parainfluenza-3 virus,
reovirus-1 and Punta Toro virus), revealing interest-
ing activities against herpes simplex virus and
vaccinia virus.
Chemistry
N′-(2-hydroxy-3-methoxybenzylidene)benzoylhy-
1
drazide (HL ) (Pouralimardan et al. 2007), N′-(2-
hydroxy-3-methoxybenzylidene)heptylhydrazide
2
(
HL ) (Carcelli et al. 2016), and N′-(2-hydroxy-3-
methoxybenzylidene)-2-hydroxybenzoylhydrazide
3
(
H L ) (Rogolino et al. 2015) were synthesized
2
following literature methods. Briefly, to a solution
of 2-hydroxy-3-methoxybenzaldehyde in absolute
ethanol, an equimolar amount of the proper
Scheme 1 Molecular
structure of the 2-hydroxy-
3
-methoxyphenyl
1
2
acylhydrazones HL , HL ,
and H L
2
3
1
23

Biometals
hydrazide in the same solvent was added. The
mixture was refluxed for 6 h, cooled at room
temperature and concentrated in vacuum. The
precipitate was filtered off, washed with cold
ethanol and dried in vacuum. The scheme of the
presence of concentrated ammonia by using Fast
Sulfon Black as indicator. Metals solutions were
acidified by adding HCl to avoid hydrolysis. The
+
concentration of the excess H was obtained by
titrating with standard KOH solution. The protona-
1
1
2
2
synthesis and the characterizations of HL , HL
tion constants of HL and HL were obtained by
titrating 20 ml of samples of each ligand
3
and H L are reported in the Supplementary Data.
2
3
−3
(
3 9 10− 0.1 mol dm ). For obtaining the complex
Potentiometric titrations
formation constants, titrations were performed in
different ligand/metal ratios (from 1 up to 4). At least
two measurements (about 60 experimental points
each) were performed for each system. The software
HYPERQUAD (Gans et al. 1996) was used for
extracting the speciation and the logarithm of the
stability constants (log βpqr) from experimental
The procedure for potentiometric titration is
described in full details elsewhere (Fisicaro and
Braibanti 1988; Gran 1952). Briefly, equilibrium
constants for protonation and complexation were
determined by means of potentiometric titrations in
p
q
r
methanol:water = 9:1 v/v solutions, ionic strength
3
titration data. βpqr = [M L H ]/[M] [L] [H] indicates
p
q r
0
.1 mol dm− KCl. Titrations were carried out under
the cumulative formation constant for the equilibrium
nitrogen in the pH range 3–11 by using a fully
automated apparatus; temperature (25 ± 0.1 °C) was
controlled to ± 0.1 °C by using a thermostatic
circulating water bath (ISCOGTR 2000 IIx). The
pM + qL + rH ⇄ M L H , where M is the metal, L
the completely deprotonated ligand and H the proton.
p
q r
Charges are omitted for simplicity.
electrodic chain (Crison 5250 glass electrode and
3
Isothermal titration calorimetry (ITC)
0
.1 mol dm− KCl in methanol:water = 9:1 v/v
calomel electrode, Radiometer 401) was calibrated in
+
terms of [H ] by means of a strong acid—strong base
ITC measurements were carried out on a CSC model
5300 N-ITC III isothermal titration calorimeter
(Calorimetry Sciences Corporations, USA) at 25 °C.
titration by Gran’s method (Gran 1952) (E
−3
°
= 371.5 ± 0.4 mV, pK = 14.40 ± 0.05). Appro-
w
KOH solution (0.065–0.145 mol dm ) in methanol:
water = 9:1 at 0.1 mol dm− KCl ionic strength was
injected in steps of 5 μL into a 960 μL reaction cell
by a 250 μL syringe with an interval of 400-500 s
between two successive injections, with stirring
speed of 150 revolutions per minute (rpm), following
the procedure previously described (Fisicaro et al.
2014). For obtaining the protonation heat of the
ligand, the cell was filled up with a solution of the
ligand in methanol:water = 9:1, 0.1 mol dm− KCl
ionic strength. Dilution heats were subtracted by
carrying out blank experiments, in which the KOH
3
priate aliquots of ligand solution, prepared by weight,
with and without metal ions, were titrated with a
KOH solution (methanol:water = 9:1 v/v, I = 0.1
3
0
.1 mol dm− KCl), whose titre was determined by
using potassium phthalate as primary standard. The
concentrations of the Mg(II) and Mn(II) stock
solutions (from MgCl ·6H O and MnCl ·4H O) were
2
2
2
2
determined by using EDTA, the sodium salt of
Eriochrome black T and NH /NH Cl as a buffer. The
3
3
4
concentration of the Cu(II) stock solution (from
CuCl ∙2H O) was determined by using EDTA in the
2
2
Scheme 2 (left) The
coordinating motif of HL ,
1
2
3
2
HL and H L ; (right) four
deprotonated hydroxyl
hydrogens of four ligands
bridge the copper(II) ions.
The four oxygens and the
four copper(II) ions form
the molecular core of a
4 4
Cu (ligand) complex
123

Biometals
Table 1 Thermodynamic parameters for the protonation of the ligands under study at 298 K
ΔG (kJ mol−1
∅
)
ΔH (kJ mol−1
∅
)
∅
ΔS (kJ mol−1
)
log β011
1
2
3
HL
HL
10.63 (1)
11.18 (1)
12.11 (1)
20.54 (1)
− 60.72 (2)
− 63.9 (2)
− 69.1 (2)
− 117.2 (2)
− 15.7 (7)
− 11.1 (2)
− 16.6 (7)
− 24.5 (7)
151 (4)
177 (3)
176 (10)
311 (10)
HL log β011
log β012
In brackets the standard deviation on the last figure
1
Fig. 1 a Raw data from the ITC titration for the protonation of
HL . Upward peaks indicate an exothermic reaction. Each
μmoles of HL in the cell, titrant KOH 0.1 mol dm−3, both in
1
−3
2
MeOH:H O = 9:1 and KCl 0.1 mol dm . The molar fraction
1
1
peak corresponds to a single 5 μl injection. b Comparison
between experimental (◊) and computed (+) stepwise heats
of HL (blue curve) and of L (red curve) are also shown
versus titrant volume in μl. (Color figure online)
(
output from HypΔH software). Experimental conditions: 5.7
solution was injected into the same solvent, without
were performed in 96-well plates containing semi-
confluent cell cultures to which 100 CCID50 (50%
cell culture infective dose) of virus was added
together with serial dilutions of the compounds.
When maximal CPE was reached, i.e. at 3–6 days
post infection, microscopy was performed to score
the virus-induced CPE. Compound cytotoxicity was
also determined by microscopy, using a mock-
infected plate.
ligand. The molar enthalpy change for the reaction
+
H
+ OH− ⇄ H O was obtained by titrating a
solution of HCl (in the cell) by KOH, in the burette,
2
both prepared in methanol:water = 9:1 at ionic
−
3
strength 0.1 mol dm
KCl. It results − 20.6
1
±
0.4 kJ mol− (Fisicaro et al. 2014). The experimen-
tal peaks were integrated and corrected for the
dilution heats by the NanoAnalyze (TA Instrument)
software. The data so obtained were elaborated by the
HypΔH software (Gans et al. 2008), assuming the
protonation
constants
from
potentiometric
Results and discussion
measurements.
1
2
3
HL , HL and H L share a common synthon, the
2
Cells and viruses
3-methoxysalicyl aldehyde; when it is reacted with an
hydrazide, a coordinating environment is formed with
two sites, an OO′ bidentate and an ONO′ tridentate
one. The solid state X-ray characterization of the
complexes of this type of ligands with Cu(II) and Mn
(II) is sufficiently extended. In particular, two types
of species have been isolated, both of them with a 1/1
The antiviral cytopathic effect (CPE) reduction
assays were performed in three different cell lines
infected with diverse DNA or RNA viruses (see
Antiviral activity for specific names of cells and
viruses) (Rogolino et al. 2015). These experiments
1
23

Biometals
3
Table 2 Logs of the protonation and the complexes formation
considered monoprotic, so that L = HL ) with Mg(II), Mn(II)
and Cu(II), in the mixed solvent MeOH:H O = 9:1
p
q
r
1
constants (βpqr = [M
p
L
q
H
r
]/[M] [L] [H] ) of the ligands HL
2
2
3
3
2
and HL and H(HL ) (for comparison purposes H L is here
1
2
3
p
q
r
HL
HL
H(HL )
0
1
1
10.63 (1)
11.18 (1)
8.43 (1)
2.8 (2)
Mg(II)
1
1
2
0
0
5.04 (4)
9.45 (3)
5.29 (6)
9.47 (4)
1
Mn(II)
1
1
2
0
0
7.1 (1)
7.7 (1)
5.34 (7)
1.84 (1)
1
12.0 (4)
13.3 (3)
Cu(II)
1
1
1
1
1
1
2
2
0
12.0 (3)
7.6 (3)
11.84 (6)
6.41 (6)
− 1
− 1
− 2
10.9 (3)
− 0.8 (3)
10.12 (7)
− 2.03 (7)
Standard deviations on the last figure are shown in brackets
metal/ligand ratio: depending on the reaction condi-
tions, it is possible to obtain a dimetallic, dimer
complex (Scheme 2) (Ray et al. 2009; Vrdoljak et al.
allowing evaluation of the enthalpic and entropic
components (Eqs. 1 and 2):
;
DG ¼ ÀRT ln b
ð1Þ
ð2Þ
pqr
2
016) or, in the case of Cu(II), a tetrameric complex
Ray et al. 2009; Rogolino et al. 2015).
On the contrary, the solution chemistry of HL ,
(
;
;
;
DG ¼ DH À TDS
1
2
3
The experimental heats from isothermal calorime-
try titration, subtracted of the dilution heats, were
processed by HypΔH software (Gans et al. 2008),
assuming the protonation constants from the poten-
tiometric measurements. Results are reported in
Table 1. The protonation of all the ligands is favored
from both the entropic and the enthalpic factors. In
Fig. 1, an example of a microcalorimetric titration
output and the comparison between experimental and
HL and H L is relatively undeveloped. We are
2
particularly interested in their speciation with metal
ions that are relevant for biological activity, as Cu(II),
Mn(II) and Mg(II). For this reason, potentiometric
titrations were carried out in mixed solvent methanol/
water = 9/1 (ionic strength = 0.1 mol dm− KCl),
where these ligands are soluble in the millimolar
range, to be consistent with our previous studies
about ligand of pharmaceutical interest but poorly
soluble in water (Bacchi et al. 2011; Rogolino et al.
3
1
computed stepwise heats for HL from the HypΔH
2
3
output are shown. Data for HL and H L are
2
014, 2015). First, the protonation constants of the
2
presented in the Supplementary Data.
ligands were determined. The pK s are 10.63(1) for
a
1
2
As far as the formation of the complexes between
HL , 11.18(1) for HL , and 8.43(1) and 12.11(1)
1
2
2+
2+
3
HL and HL and Mg and Mn metal ions is
concerned, unfortunately we had to deal with poor
solubility of the species formed in solution, especially
(
Rogolino et al. 2015) for H L . It seems reasonable
2
to consider that the 2-hydroxy group is the first one to
dissociate (Ali Kamyabi et al. 2008). Effectively,
2
+
1
2
3
with Mn
ions. The solution started to become
1
HL and HL are diprotic (OH and NH), and in H L
2
turbid in the range 8 \ pH \ 11 for HL and
.5 \ pH \ 11.5 for HL , with metal:ligand ratio
:2. At higher pH the precipitate dissolved again.
another OH group is present, but the methanol/water
2
7
1
(
9/1) solvent seems to lower acidity so that the higher
pKa is not detected by potentiometric titration.
The thermodynamics of the protonation of the
three ligands were determined by ITC experiments,
2
+
When Mg is considered, the solutions were cloudy
at pH [ 8.5. Obviously, only the experimental points
123

Biometals
Fig. 2 Distribution diagrams for the systems ligand:M(II) = 4:1 (M(II) concentration = 1.25 9 10 mol dm−3). (a) HL -Mg(II);
−
3
1
1
2
2
(
b) HL -Mn(II); (c) HL -Mg(II); (d) HL -Mn(II). Charges were omitted for simplicity
Fig. 3 Distribution diagrams for the systems ligand:Cu(II) = 4:1 (Cu(II) concentration = 1.25 9 10 mol dm−3). (a) HL -Cu(II);
−
3
1
2
(
b) HL -Cu(II). Charges were omitted for simplicity
1
23

Biometals
1
2
3
2
Table 3 Antiviral activity of HL , HL , and H L in cell culture assays
a
b
Compound
Antiviral EC50 (µM) in HEL cells infected with
Minimal cytotoxic concentration (µM) in
Herpes simplex virus-1
Vaccinia virus
Adenovirus type 2
HEL
HeLa
Vero
1
HL
6.4
8.9
1.6
0.95
6.8
8.9
1.3
16
[ 100
[ 100
[ 100
7.9
≥ 100
≥ 100
60
20
20
4
≥ 20
[ 100
20
2
HL
3
2
H L
c
Cidofovir
[ 250
nd
nd
Cell lines used: HEL, human embryonic lung fibroblast cells; HeLa, human cervix carcinoma cells; Vero, African Green monkey
kidney cells
a
EC50: 50% effective concentration, i.e. compound concentration producing 50% inhibition of virus-induced CPE, determined by
microscopy. Compounds are not active against: vesicular stomatitis virus, Coxsackie B4 virus or respiratory syncytial virus (assessed
in HeLa cells), parainfluenza-3 virus, reovirus-1 and Punta Toro virus (assessed in Vero cells)
b
Compound concentration producing minimal alterations in cell morphology, determined by microscopy
c
Cidofovir used as reference drug
nd not done
in which the solution appeared clear were processed
by using HYPERQUAD software (Gans et al. 1996).
The models of speciation showing the best statistical
parameters and the best fit between experimental and
computed potentiometric titration curves are shown
in Table 2. The distribution diagrams as a function of
pH, evaluated for metal to ligand ratio = 4:1, are
reported in Fig. 2. It can be gathered that the
enhances very much the acidity of the hydrazonic
nitrogen, so that a bidentate NO chelate forms in the
inner coordination sphere. The distribution diagrams
as a function of the pH for Cu(II):ligand = 4:1, are
shown in Fig. 3. Comparison of the distribution
diagrams in Figs. 2 and 3 clearly proves that the
complexation of Cu(II) starts already at low pH,
unlike that of Mg(II) and Mn(II), due to the
insoluble species is ML , the neutral one. For Mn(II),
2
pronounced difference in affinity. The presence of
3
we processed also the points at the highest pH in
another phenolic OH group in H L enhance the
2
which the solution was clear, and we were able to find
1
affinity for Cu(II) ions (Table 2) and in addition
allows the formation of polynuclear species, as
elsewhere discussed and also characterized by single
crystal X ray diffraction (Rogolino et al. 2015).
out the species MnL HÀ1 [log β
= 0.8(4)] and
1 2 −1
2
1
2
MnL HÀ2 [log β
= − 11.3(6)] and, similarly for
1 2 −2
the other ligand, MnL H [log β1 2 −1 = 2.0(4)] and
2
2
À1
2
2
MnL HÀ2 [log β
= − 11.8(4)], with high
1 2 −2
confidence. These species, not reported in Table 2
because they form at a pH in which it is generally
assumed that the glass electrode does not work
perfectly, explain the redissolution at high pH. They
are probably hydroxylated species derived from the
dissociation of water molecule in the inner coordina-
tion sphere.
Antiviral activity
1
2
3
The three compounds HL , HL and H L underwent
2
broad antiviral evaluation against a variety of DNA
and RNA viruses, in three cell lines, i.e. human
embryonic lung (HEL) fibroblast cells, human cervix
carcinoma cells (HeLa), and African Green monkey
kidney cells (Vero). Interestingly, in the HEL assays,
the three compounds displayed activity against the
enveloped DNA viruses herpes simplex virus type 1
The Cu(II) ion showed higher affinity for the
ligands and a different behavior was observed in
solution. For example, the systems with Cu(II) and
1
2
HL and HL were clear all through the examined pH
range, before becoming pale yellow and then turning
to pale green at higher pH. The species giving rise to
the best fit between computed and experimental
titrations, reported in Table 2, suggest that Cu(II)
and vaccinia virus, yet were inactive against aden-
3
ovirus, a naked DNA virus. H L was the most active
2
one, with an antiviral EC50 value of ~ 1.5 µM and a
minimal cytotoxic concentration of 60 µM, yielding a
favourable selectivity index (ratio of cytotoxic to
123

Biometals
antiviral concentration) of 40. About 5-fold lower
activity and selectivity was seen with the other two
HIV-1 IN strand transfer chelating inhibitors: a focus on
metal binding. Mol Pharm 8:507–519
Bleichert P, Esp `ı rito Santo Ch, Hanczaruk M, Meyer H, Grass
G (2014) Inactivation of bacterial and viral biothreat
agents on metallic copper surfaces. Biometals 27:1179–
1189
Carcelli M, Rogolino D, Gatti A, De Luca L, Sechi M, Kumar
G, White SW, Stevaert A, Naesens L (2016) N-acylhy-
drazone inhibitors of influenza virus PA endonuclease
with versatile metal binding modes. Sci Rep 6:31500
Chana AN, Shiverb AL, Weverc WJ, Zeenat S, Razvid A,
Traxlere MF, Lia B (2017) Role for dithiolopyrrolones in
disrupting bacterial metal homeostasis. PNAS 114:2717–
1
2
molecules, HL and HL . Neither of the three
compounds was active against any of the other
viruses, i.e. vesicular stomatitis virus, Coxsackie B4
virus or respiratory syncytial virus, assessed in HeLa
cells, and parainfluenza-3 virus, reovirus-1 and Punta
Toro virus, assessed in Vero cells (data not shown).
Finally, we noticed that the cytotoxicity of the
compounds was more pronounced in Vero and, in
particular, HeLa cells, when compared to HEL cells
2
722
(
Table 3).
Fisicaro E, Braibanti A (1988) Potentiometric titrations in
methanol/water medium: intertitration variability. Talanta
1
0:769–774
Fisicaro E, Compari C, Bacciottini F, Contardi L, Carcelli M,
Rispoli G, Rogolino D (2014) Thermodynamics of com-
plexes formation by ITC in methanol/water = 9/1 (v/v)
solution: a case study. Thermochim Acta 586:40–44
Gans P, Sabatini A, Vacca A (1996) Investigation of equilibria
in solution. Determination of equilibrium constants with
HYPERQUAD suite of programs. Talanta 43:1739–1753
Gans P, Sabatini A, Vacca A (2008) Simultaneous calculation
of equilibrium constants and standard formation enthal-
pies from calorimetric data for systems with multiple
equilibria in solution. J Solut Chem 37:467–476
Gran P (1952) Determination of the equivalence point in
potentiometric titrations. Part II. Analyst 77:661–671
Helsel ME, Franz KJ (2015) Pharmacological activity of metal
binding agents that alter copper bioavailability. Dalton
Trans 44:8760–8770
Conclusions
The polydentate acylhydrazonic molecules HL , HL
1
2
3
and H L are able to interact with some essential
2
metal ions as Mg(II), Mn(II) and Cu(II). Depending
on the R group (Scheme 1) in their structure, the
coordinating behavior is different. Despite some
solubility problems, it is possible to say that these
3
ligands in general and H L in particular show a
2
preference for Cu(II). It is perhaps premature to
3
correlate the higher affinity of H L for Cu(II) with
2
its good antiviral activity against herpes simplex and
vaccinia virus (EC50 ~ 1.5 µM, minimal cytotoxic
concentration = 60 µM, selectivity index = 40), but
the idea of antivirals that can act by perturbation of
copper homeostasis (Bleichert et al. 2014; Warnes
and Keevil 2013) is fascinating and deserve further
experimental efforts.
Jiang Q, Sicking W, Ehlers M, Schmuck C (2015) Discovery of
potent inhibitors of human β-tryptase from pre-equili-
brated dynamic combinatorial libraries. Chem Sci
6
:1792–1800
Kim B, Ko H, Jeon E, Ju E, Jeong LS, Kim Y (2016) 2,3,4-
Trihydroxybenzyl-hydrazide analogues as novel potent
coxsackievirus B3 3C protease inhibitors. Eur J Med
Chem 120:202–216
Acknowledgements ‘‘Centro Interdipartimentale Misure
Giuseppe Casnati” of the University of Parma is thanked for
facilities.
Pouralimardan O, Chamayou A, Janiak Ch, Hosseini-Monfared
H (2007) Hydrazone Schiff base-manganese(II) com-
plexes: synthesis, crystal structure and catalytic reactivity.
Inorg Chim Acta 360:1599–1608
Ray A, Rizzoli C, Pilet G, Desplanches C, Garribba E, Ren-
tschler E, Mitra S (2009) Two new supramolecular
architectures of singly phenoxo-bridged copper(II) and
doubly phenoxo-bridged manganese(II) complexes
derived from an unusual ONOO donor hydrazone ligand:
syntheses, structural variations, cryomagnetic, DFT, and
EPR studies. Eur J Inorg Chem 20:2915–2928
Author’s contributionsThe manuscript was written through
contributions of all authors. All authors have given approval to
the final version of the manuscript.
References
Rogolino D, Carcelli M, Compari C, De Luca L, Ferro S,
Fisicaro E, Rispoli G, Neamati N, Debyser Z, Christ F,
Chimirri A (2014) Diketoacid chelating ligands as dual
inhibitors of HIV-1 integration process. Eur J Med Chem
Ali Kamyabi M, Shahabi S, Hosseini-Monfared H (2008)
Spectrophotometric and potentiometric study of (E)-N′-(2-
hydroxy-3-methoxybenzylidene)benzohydrazide with
a
7
8:425–430
ferric ion in the methanol–water mixture. J Chem Eng
Data 53:2341–2345
Bacchi A, Carcelli M, Compari C, Fisicaro E, Pala N, Rispoli
G, Rogolino D, Sanchez TM, Sechi M, Neamati N (2011)
Rogolino D, Carcelli M, Bacchi B, Compari C, Contardi L,
Fisicaro E, Gatti A, Sechi M, Stevaert A, Naesens L
(2015) A versatile salicyl hydrazonic ligand and its metal
complexes as antiviral agents. J Inorg Biochem 150:9–17
1
23

Biometals
Sayed AM, Choi S, Lee D (2017) Synthesis, anticancer, and
docking studies of salicyl-hydrazone analogues: a novel
series of small potent tropomyosin receptor kinase A
inhibitors. Bioorg Med Chem 25:389–396
Vrdoljak V, Pavlovic´ G, Maltar-Strmecˇki N, Cindric´ M
(2016) Copper(II) hydrazone complexes with different
nuclearities and geometries: synthetic methods. New J
Chem 40:9263–9274
Vantomme G, Lehn J (2013) Photo- and thermoresponsive
+
Warnes SL, Keevil CW (2013) Inactivation of Norovirus on
dry copper alloy surfaces. PLoS ONE 8:e75017
Weekley CM, He C (2017) Developing drugs targeting tran-
sition metal homeostasis. Curr Op Chem Biol 37:26–32
supramolecular assemblies: reversible photorelease of K
ions and constitutional dynamics. Angew Chem Int Ed
52:3940–3943
123