Synthesis, spectroscopic characterization, DFT studies, and antibacterial and antitumor activities of a novel water soluble Pd(II) complex with l-alliin

Article abstract of DOI:10.1016/j.molstruc.2012.11.065

A new water soluble Pd(II) complex with l-alliin (S-allyl-l-cysteine sulfoxide) was obtained and characterized by a set of chemical and spectroscopic measurements. Elemental and mass spectrometric data are consistent with the formula [Pd(C₆H

Full text of DOI:10.1016/j.molstruc.2012.11.065

Journal of Molecular Structure 1035 (2013) 421–426
Contents lists available at SciVerse ScienceDirect
Journal of Molecular Structure
journal homepage: www.elsevier.com/locate/molstruc
Synthesis, spectroscopic characterization, DFT studies, and antibacterial
and antitumor activities of a novel water soluble Pd(II) complex with L-alliin
a
b
d
Camilla Abbehausen a, , Suelen F. Sucena , Marcelo Lancellotti , Tassiele A. Heinrich ,
⇑
Emiliana P. Abrão d, Claudio M. Costa-Neto d, André L.B. Formiga c, Pedro P. Corbi a
a Bioinorganic and Medicinal Chemistry Research Laboratory, LIQI, Institute of Chemistry, University of Campinas, UNICAMP, PO Box 6154, 13083-970 Campinas, SP, Brazil
b Laboratory of Biotechnology, Institute of Biology, University of Campinas, UNICAMP, Campinas, SP, Brazil
c Coordination Chemistry Laboratory, LIQI, Institute of Chemistry, University of Campinas, Campinas, SP, Brazil
d Department of Biochemistry and Immunology, School of Medicine of Ribeirão Preto, University of São Paulo, USP, 14049-900 Ribeirão Preto, SP, Brazil
h i g h l i g h t s
"
"
"
"
A novel water soluble Pd(II) complex with L-alliin.
The coordination was determined by IR, 1H, 13C, 15N NMR, mass spectrometry and DFT studies.
The compound shows antibacterial activity against Gram positive and Gram negative bacterial strains.
The complex also exhibits cytotoxic activities against HeLa tumorigenic cells.
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 27 October 2012
Received in revised form 28 November 2012
Accepted 28 November 2012
Available online 8 December 2012
A new water soluble Pd(II) complex with L-alliin (S-allyl-L-cysteine sulfoxide) was obtained and charac-
terized by a set of chemical and spectroscopic measurements. Elemental and mass spectrometric data are
consistent with the formula [Pd(C6H10NO3S)2]. The 1H and 13C nuclear magnetic resonance (NMR) data,
[1H–15N] two dimensional (2D) NMR and infrared spectroscopic measurements indicate coordination
of the ligand to Pd(II) through N and O atoms. DFT studies showed that the trans isomer is the most stable
and preferred geometry for the complex. The complex is soluble in water and dimethylsulfoxide. An anti-
biogram assay revealed that the complex possess antibacterial activity against Escherichia coli, Pseudomo-
Keywords:
Pd(II)
nas aeruginosa and Staphylococcus aureus bacterial strains in the range 125–500
assays revealed that the complex presents cytotoxic activity over HeLa cells with an estimated IC50 of
20
mol Lꢀ1
l
g mLꢀ1. Antitumor
L
-alliin
Infrared
NMR
l
.
Ó 2012 Elsevier B.V. All rights reserved.
Antibacterial agent
Antitumor activity
1. Introduction
and second-generation drugs based on the cisplatin structure, such
as carboplatin and oxaliplatin, are the best examples of metal-
based compounds in clinical use. Cisplatin is a chemoterapeutic
agent particularly effective against cervical, head, neck, bladder
and testicular cancer. In spite of its anticancer activity, cisplatin
has been shown to possess toxic side effects such as nephro-, neu-
ro- and hematotoxicity. Continuous efforts have been made to alle-
viate these side effects and improve its solubility, including
changes in the cisplatin structure and also the synthesis of new
anticancer compounds with other metal ions [1]. Palladium(II), as
a soft Lewis acid, has the ability to form stable chelated rings with
N,S-donor ligands [2]. Based on the similarities of coordination
geometry and thermodynamic parameters of the palladium(II)
complexes when compared to the platinum(II) analogues, synthe-
sis and application of palladium-based compounds in medicinal
Metal complexes have been considered as therapeutic agents
for a long time. Cisplatin, or cis-diamminedichloroplatinum (II),
Abbreviations: Ali, S-Allyl-L-cysteine sulfoxide; ATCC, American type collection
cell; BEC, Brazilian endemic clone; CLSI, Clinical and Laboratory Standards Institute;
DFT, density functional theory; DMEM, Dulbecco’s modified eagle medium; DMSO,
dimethylsulfoxide; D2O, deuterium oxide; ESI-MS, electrospray mass spectrometry;
FCS, fetal calf serum; HMBC, heteronuclear multiple bond correlation; IR, infrared
spectroscopy; MIC, minimal inhibitory concentration; MTT, (3-(4,5-Dimethylthia-
zol-2-yl)-2,5-diphenyltetrazolium bromide; NMR, nuclear magnetic ressonance;
PBS, phosphate buffer saline; PES, potential energy surface; Pd-Ali, palladium(II)
complex with alliin; ZPE, zero point energies.
⇑
Corresponding author.
E-mail addresses: camilla.abb@gmail.com (C. Abbehausen), ppcorbi@iqm.
unicamp.br (P.P. Corbi).
0022-2860/$ - see front matter Ó 2012 Elsevier B.V. All rights reserved.
http://dx.doi.org/10.1016/j.molstruc.2012.11.065

422
C. Abbehausen et al. / Journal of Molecular Structure 1035 (2013) 421–426
chemistry started to be considered. However, the palladium com-
pounds were reported to be kinetically more reactive than the plat-
inum analogues [3].
2. Experimental
2.1. Materials and methods
Due to the growth of multi-resistant bacterial strains, syntheses
of new antibacterial agents of silver(I), gold(I) and also platinum(II)
and palladium(II) for the treatment of infectious diseases have also
been evaluated. Kazachenko et al. [4] investigated the synthesis
and antibacterial activities of silver complexes with the amino
acids histidine and tryptophan. Both compounds showed a good
antibacterial activity against Gram-negative and Gram-positive
bacterial strains and low toxicity. In addition, the antibacterial
activities of palladium(II) complexes of tetracyclines (tetracycline,
doxycycline and chlortetracycline) have been reported [5]. The pal-
ladium(II) complex of tetracycline is practically as efficient as free
tetracycline in inhibiting the growth of two Escherichia coli sensi-
tive bacterial strains and 16 times more potent than free tetracy-
cline against E. coli HB101/pBR322, a bacterial strain resistant to
tetracycline. A palladium(II) complex with benzimidazole showing
significative antibacterial activity against Gram-negative strains,
and also antitumor activities against breast cancer (MCF7), colon
carcinoma (HCT) and human heptacellular carcinoma (Hep-G2)
has been recently described [6]. Budige et al. also described the
synthesis of Pd(II) complexes with Schiff bases with a pronounced
antibacterial activity against Bacillus subtilis and Staphylococcus
aureus [7].
L
-Deoxyalliin and lithium tetrachloropalladate(II) hydrate of
analytical grade were purchased from LKT and Sigma–Aldrich lab-
oratories, respectively. Hydrogen peroxide was obtained from
Synth and potassium hydroxide was purchased from Sigma. The
methanol used in the synthesis was previously treated and kept
over 100 g Lꢀ1 5 Å molecular sieves. Elemental analyses for carbon,
hydrogen and nitrogen were performed using a Perkin-Elmer 2400
CHNS-O analyser. Electrospray mass spectrometric (ESI-MS) mea-
surements were carried out using a Waters Quattro Micro API.
Samples were evaluated in the positive mode in an 1:1 acetoni-
trile:water solution with addition of 0.10% (v/v) formic acid. The
infrared (IR) spectra were measured using a Bomem MB-Series
Model B100 FT-IR spectrophotometer in the range 4000–
400 cmꢀ1 with resolution of 4 cmꢀ1. Samples were prepared as
KBr pellets. The 1H, 13C and [1H–15N] NMR spectra were recorded
on a Bruker 400 MHz Avance II (9.395 T). The 1H NMR spectra were
acquired at 400 MHz while the 13C were acquired at 100 MHz. Two
dimensional [1H–15N] NMR data were acquired at 40.55 MHz for
15N and 400 MHz for 1H. Samples were prepared in deuterium
oxide (D2O).
Amino acids are molecules of high interest for pharmacological
applications. In general, amino acids have been shown to possess
low toxicity and high affinity to specific sites in the body. In addi-
tion, amino acids contain at least two coordination sites, the amino
group and the carboxylic group. They can also have a third
coordination site when a sulfur atom is present, as observed with
cysteine, methionine and their derivatives. In our group palla-
dium(II) complexes of methionine sulfoxide and deoxyallin were
synthesized, characterized and their antitumor activities evaluated
against HeLa, tumorigenic cells, with promising results [8,9]. The
Pd(II) complex with deoxyalliin was also shown to posses
antibacterial activities against pathogenic bacterial strains of S.
aureus and E. coli [10]. More recently, Carvalho et al. published
the antibacterial activities of Ag(I) and Pd(II) complexes with tryp-
tophan. The Ag(I) complex was also cytotoxic against Panc-1 (hu-
man pancreatic carcinoma) and SK-Mel 103 (human melanoma)
cells [11,12].
2.2. Synthesis of
L-alliin
L-alliin was obtained from the amino acid L-deoxyalliin by an
oxidative process with hydrogen peroxide in a procedure similar
to that described in the literature [18,19]. Anal. Calcd for
C6H11NO3S ꢁ 0.5 H2O (%): C 38.7 H 6.51 N 7.52. Found (%):
C 38.1 H 6.29 N 7.49.
2.3. Synthesis of the Pd-alliin complex
The palladium(II) complex with alliin (Pd-Ali) was synthesized
by the reaction of 0.50 ꢁ 10ꢀ3 mol of lithium tetrachloropalla-
date(II) hydrate, Li2[PdCl4]ꢂxH2O, in methanolic solution (4.0 mL)
with the freshly prepared potassium salt of alliin containing
1.0 ꢁ 10ꢀ3 mol of the ligand, also in methanol (10 mL). The synthe-
sis of the complex was carried out with stirring. A pale yellowish
solid of the complex was slowly precipitated. After 2 h of constant
stirring, the precipitate was filtered, washed with cold water and
dried in a desiccator over P4O10. Anal. Calcd for Pd (C6H10NO3S)2ꢂ
2H2O (%): C 29.1 N 5.66 H 4.90. Found (%): C 28.4 N 5.62 H 4.54.
The complex is soluble in water and dimethylsulfoxide (DMSO).
S-allyl-L-cysteine sulfoxide (C6H11NO3S, Ali) is a sulfur
containing amino acid present in garlic and onion bulbs. The
medicinal properties of Allium species have been studied for cen-
turies. However the mode of action of the garlic components is
still uncertain. It has been found that Allium compounds exhibit
immune system improvement, and antibacterial and antifungal
actions [13,14]. The major components of garlic oil were isolated
in 1944 [15,16]. The most abundant compounds were diallyl
disulfide and allicin. Alliin and the product of its enzymatic
decomposition (allicin) were isolated in 1948 [13]. Extracts
containing allicin displayed the most prominent antimicrobial
properties. Other cysteine sulfoxides and their corresponding
thiosulfinates were isolated latter. Nevertheless, the antibacterial
and antifungal properties are still attributed to allicin. More re-
cently, garlic preparations were evaluated against human tumor
cells with promising results [17]. Alliin was found to be inactive
against bacteria and tumor cells, but it acts as allicin generator
in situ [13].
2.4. Molecular modeling
Geometric optimizations were carried out using GAMESS soft-
ware [20] with a convergence criterion of 10ꢀ4 a.u. in a conjugated
gradient algorithm. The LANL2DZ effective core potential was used
for the palladium atom and the atomic 6-31G(d) basis set [21–25]
for all other atoms. Density functional theory (DFT) calculations
were carried out using B3LYP [26,27] gradient-corrected hybrid
to solve the Kohn–Sham equations with a 10ꢀ5 a.u. convergence
criterion for the density change. The bidentated coordination
through carboxylate and amino groups was confirmed as mini-
mum of the potential energy surface (PES) with calculations of
the Hessians showing no imaginary frequencies.
The first platinum(II) complex with alliin was initially synthe-
sized in our laboratories. Preliminary cytotoxic studies indicate
moderated activity of the complex toward HeLa cells [18]. Here,
we report the synthesis, spectroscopic characterization, DFT
studies and antibacterial and antitumor activities of a new water
2.5. In vitro assays with tumor cells
HeLa cells (ATCC CCL-2) were cultured in Dulbecco’s modified
eagle’s medium (DMEM) supplemented with 10% of fetal calf
soluble Pd(II) complex with L-alliin.

C. Abbehausen et al. / Journal of Molecular Structure 1035 (2013) 421–426
423
serum (FCS), using streptomycin and penicillin as antibiotics, in an
atmosphere of 5% CO2 at 37 °C. All cell culture reagents were
purchased from Costar (Corning Inc., NY). The 3-(4,5-dimethylthi-
azol-2-yl)-2,5-diphenyltetrazolium salt (MTT) was acquired from
Sigma. Cells were placed in a 48-well plate (4 ꢁ 104 cells/well)
24 h prior to the beginning of the experiment. A stock solution of
the Pd-Ali complex was prepared in phosphate buffer saline
(PBS), which was diluted into the cells medium in order to achieve
different concentrations. Forty-eight hours after addition of the
complex, MTT salt was added (aiming for a final concentration of
0.50 mg mLꢀ1) and the cells were incubated with this reagent for
a period of 3 h [28]. After the incubation period, cells were washed
with PBS and isopropanol was added. The cell viability was
determined by absorbance measurements at 570 nm.
Fig. 1. Structure of alliin with carbon and hydrogen atoms numbered.
The 13C NMR spectrum of the alliin and Pd-Ali are shown in
Fig. 2. The 13C NMR spectrum of alliin and Pd-Ali consists of two
defined sets of resonances for the carbons C2, C3, C4 and C5. The
occurrence of two sets of resonance frequencies is due to the pres-
ence of an asymmetric center on the sulfur atom, which was not
2.6. Antibacterial assays
observed in the case of L-deoxyalliin [18]. A comparison between
An antibiogram assay was carried out in order to evaluate the
antibacterial activities of the Pd-Ali complex. Six pathogenic bacte-
rial strains, E. coli ATCC 25922, Pseudomonas aeruginosa ATCC
27853, P. aeruginosa 31NM, S. aureus ATCC 25923, S. aureus
BEC9393 and S. aureus Rib1, were selected. Bacterial susceptibili-
ties were performed by the well diffusion method in accordance
with Bauer et al. and confirmed by determination of minimal
inhibitory concentration (MIC) as recomended by the Clinical and
Laboratory Standards Institute (CLSI) [29,30]. Commercial antibi-
otic discs of ofloxacin and imipenen were used as positive controls.
The MIC values were determined by the following methodology.
Stock solutions (10.0 mg mLꢀ1) of Pd-Ali in water were prepared
before the experiments. Samples were submitted to serial dilutions
the NMR spectra of the ligand and the complex permit us to con-
firm the coordination of the ligand to the metal through the N atom
of amino group and the O atom of carboxylate group. In the free li-
gand the chemical shift at 171.4 ppm is assigned to the carbon of
COOH group (C1 in Fig. 1). In the spectrum of the complex this sig-
nal is shifted downfield by 11 ppm, being observed at 182.4 ppm.
This shift shows the coordination through the oxygen atom of
the carboxylate group [31,32]. A significative change is also ob-
served for the chemical shift assigned to C2 when the spectra of
the complex and the ligand are compared. These signals are ob-
served at 50.2 ppm and 54.0 ppm in ligand and the complex spec-
tra, respectively, indicating coordination of the ligand to the metal
through the nitrogen atom. The spectra also show a shift of
2.9 ppm for carbon C3. No change is observed in the C4 and C5
chemical shifts, which demonstrate that alliin is not coordinate
to the metal through the sulfur or oxygen atoms of the sulfoxide
group. The 13C chemical shifts for Ali and Pd-Ali are given in
Table 2.
(1:1) in a 96 well multiplate with 100.0 lL of each Pd-Ali dilution
and then transferred to the plates containing the respective bacte-
rial strain in seven decreasing concentrations. The plates were sub-
mitted to 37 °C for 24 h.
3. Results and discussion
The coordination through the nitrogen atom of the NH2 was
evaluated by 15N NMR. The 15N chemical shifts for Ali and Pd-Ali
were indirectly obtained from the 2D spectra via the heteronuclear
3.1. Mass spectrometric data
The most significant m/z peaks in electrospray mass spectrum of
alliin and Pd-Ali complex are described in Table 1.
The mass spectrum of alliin shows the presence of the molecu-
lar ion at m/z 178. The dimeric species was observed at m/z 355.
The spectrum of the Pd-Ali complex shows one peak with m/z
459 corresponding to the [Pd (C6H10NO3S)2+H]+ molecular ion.
Other fragment species are also observed. The mass spectrometric
data confirmed the palladium/alliin composition of 1:2.
3.2. NMR spectroscopic measurements
Solution state 13C and [1H–15N] NMR spectra of the Pd-Ali com-
plex were analyzed by comparison with the NMR spectra of pure
Ali. The structure of alliin with carbon and hydrogen atoms num-
bering is presented in Fig. 1.
Table 1
Electrospray mass signals m/z and relative abundances of Ali and Pd-Ali (ESI+).
Compounds
Ion assignment
m/z
Rel. Abundance (%)
[C6H11NO3S + H]+
[(C6H11NO3S)2 + H]+
[C6H11NO2S + H]+
178
355
161
100
30
25
Ali
[Pd(C6H11NO3S)2 + H]+
[Pd(C6H10NO3S) + H]+
[Pd(C4H7NO3S) + H]+
459
282
238
75
65
28
Pd-Ali
Fig. 2. 13C NMR of Ali and Pd-Ali. Assignment of the carbons are presented
according to Fig. 1.

424
C. Abbehausen et al. / Journal of Molecular Structure 1035 (2013) 421–426
Table 2
13C chemical shifts for Ali and Pd-Ali.
Compounds
Chemical shifts (ppm)
C1
C2
C3
C4
C5
C6
Ali
Pd-Ali
171.4
182.4
50.22
53.99
49.71
52.60
54.66
54.81
125.5
125.6
124.4
124.6
[1H–15N] multiple bond coherence technique (HMBC), as decribed
for other metal complexes with N donor ligands [31–33]. The 15N
spectra are provided in Fig. 3. The nitrogen signal was observed
by its correlation with hydrogens H3a and H3b in Fig. 1. The chem-
ical shift for nitrogen in the ligand was observed at 40 ppm and for
the complex at ꢀ20 ppm. The
Dd of 60 ppm reinforces the coordi-
nation of alliin to palladium through the nitrogen atom of NH2
group.
Fig. 4. Infrared spectra of Ali and Pd-Ali.
3.3. Infrared absorption spectroscopy
A strong and sharp absorption band at 1022 cmꢀ1 is present in
both spectra at the same frequency and intensity, being assigned to
the S@O streching mode. The observed results reinforce the non-
coordination of the sulfoxide group to Pd(II) as proposed when
considering the NMR data.
The infrared spectrum of the Pd-Ali complex was analyzed in
comparison to the spectrum of the free ligand (Ali). Both spectra
are presented in Fig. 4.
According to the literature, the presence of two resolved bands
in the region of 3000–3400 cmꢀ1 is an indication of coordination of
the amino group to metal ions in amino acids [34,35]. The IR spec-
3.4. Molecular modeling
trum of alliin has a broad band in the range 3100–2700 cmꢀ1
,
which is assigned to NH2 and CH2 stretching modes. Enlargement
of this band is due to the presence of hydrogen bonding. In the
spectrum of the complex two bands can be identified at 3215
and 3103 cmꢀ1 corresponding to NH2 asymmetric and symmetric
stretching modes, respectively. In addition two bands at
1516 cmꢀ1 and 1538 cmꢀ1, assigned to NH2 deformation, are pres-
ent in the spectrum of the free ligand. The absence of these bands
in the IR spectrum of the complex is another valuable proof of
coordination of the ligand to Pd(II) through the NH2 group. The
IR spectrum of the Pd-Ali complex shows the asymmetric and sym-
metric stretching modes of carboxylate group at 1651 cmꢀ1 and at
1379 cmꢀ1. In the free ligand spectrum, these bands are observed
at 1650 cmꢀ1 and at 1394 cmꢀ1. Since the difference between the
The proposition of a bidentate coordination of two alliin mole-
cules to Pd(II), through nitrogen and oxygen atoms, as evidenced
by the spectroscopic evaluations, was calculated using DFT for
the cis and trans isomers. Equilibrium geometries were confirmed
by vibrational analysis showing no imaginary frequencies. The
energies were corrected by adding zero point energies (ZPE) and
they were compared for the isomers. The results demonstrated
that the most stable form is the trans isomer, by 6.6 kcal molꢀ1
.
The calculated distances and angles in the coordination sphere
are described in Table 3. The optimized structure is in good agree-
ment with the crystallographic data found in the literature for
other ligands N,O- coordinated to palladium(II) [36–39]. The opti-
mized structure can be found in Fig. 5.
asymmetric and symmetric stretching modes,
D, is larger in the
The simulated IR spectrum of the free ligand is also in agree-
ment with the experimental data. The bands related to the amino
group can be observed at 3459 cmꢀ1 and 3359 cmꢀ1 for assymmet-
ric and symmetric stretching modes, respectively. These bands are
shown in a very low intensity, which can explain the very broad
band observed in the experimental spectrum assigned to the NH2
and CH2 stretching modes. The NH2 deformation mode is present
at 1599 cmꢀ1 and the C@O and S@O stretching modes can be seen
at 1599 cmꢀ1 and 1016 cmꢀ1, respectively, confirming the assign-
ment in the experimental spectrum. The simulated spectrum of
the complex shows a weak absorption at 3359 cmꢀ1 and a strong
absorption at 3159 cmꢀ1. The changes, mainly in the intensity of
the modes can explain the appearance of well resolved bands in
the experimental data, confirming the coordination of this group
to the metal ion. The calculated spectrum of the complex shows
that the low intensity NH2 deformation mode has a shift to higher
spectrum of the complex when compared to that of the ligand, a
monodentate coordination of the carboxylate group through the
oxygen atom is proposed. In this case,
D
(COOꢀ) for the complex
is 272 cmꢀ1, while for the ligand, this value is 257 cmꢀ1
.
Table 3
Selected distances (Å) and angles (°) for trans-palladium(II) complex with L-alliin as
calculated by B3LYP/DFT.
Distances (Å)
Angles (°)
Pd–O
Pd–N
Pd–O0
Pd–N0
2.025
2.089
2.024
2.089
O-Pd–N
O-Pd–O0
O0–Pd–N0
N–Pd–N0
81.76
177.98
81.59
178.38
Fig. 3. [1H–15N] HMBC spectra of Ali and Pd-Ali.

C. Abbehausen et al. / Journal of Molecular Structure 1035 (2013) 421–426
425
and 500 l
g mLꢀ1. The ligand itself did not exhibit any antibacterial
activity under the same experimental conditions. Antibiotic sensi-
tive profiles of bacterial strains are listed in Table 4. The observed
results are comparable to a the Pd(II) complex with deoxyalliin
[10]. As observed in that case, the activity of the Pd-Ali complex
is most probably due to the presence of the Pd(II) ions since the
ligand itself is inactive for the same bacterial strains in the
considered conditions.
4. Conclusions
Fig. 5. Optimized structure of trans-Pd-Ali complex obtained by B3LYP/DFT using
LANL2DZ (Pd) 6-31G (d) basis set. Pd (yellow), N (blue), O (red), C (orange) and H
(white). (For interpretation of the references to color in this figure legend, the
reader is referred to the web version of this article.)
A new water soluble palladium(II) complex with L-alliin with a
1:2 M composition (metal:ligand) was obtained and structurally
characterized. The 1H, 13C and 15N NMR spectroscopies and, IR
and mass spectrometric measurements support coordination of
the ligand to Pd(II) via the nitrogen atom of the amino group and
an oxygen atom of the carboxylate group, forming a five membered
chelated ring. DFT studies suggest that the trans geometry is
strongly preferred and probably the only configuration present in
the complex. The calculated infrared frequencies compared with
experimental data also support this structure. A schematic struc-
ture for the Pd-Ali complex is shown in Fig. 5.
The in vitro cytotoxic assays revealed the antitumor activity of
the complex over HeLa cells while no activity was detected for L-
alliin. Antimicrobial studies revealed antibacterial activity of the
complex against Gram-positive and Gram-negative microorgan-
isms in the range 125–500 l .
g Lꢀ1
Fig. 6. Cytotoxic analyses of Pd-Ali in different concentrations (l
mol Lꢀ1) against
HeLa cells. Data from three different experiments were normalized to the
maximum values obtained for the control group and are expressed as mean s.e.m.
Acknowledgements
This study was supported by grants from FAPESP (Proc. 2012/
08230-2) and CNPq (Brazilian agencies). The authors are also
grateful to Professor Carol H. Collins for the English revision of
the manuscript.
Table 4
Antibiotic sensitive profile of the Pd-Ali complex against the considered bacterial
strains.
S. aureus S. aureus S. aureus
P. aeruginosa P. aeruginosa E. coli
BEC 9393 Rib1
ATCC25923 ATCC27853
31NM
ATCC25922
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Minimal inhibitory concentration (
l
g mLꢀ1
500.0
)
500.0
250.0
500.0
250.0
125.0
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