Synthesis, characterization and antiproliferative activity of transition metal complexes with 3-(4,5-diphenyl-1,3-oxazol-2-yl)propanoic acid (oxaprozin)

Article abstract of DOI:10.1248/cpb.c12-00185

A series of novel Mn(II), Co(II), Ni(II), Cu(II) and Zn(II) complexes with oxaprozin (Hoxa), a non-steroidal anti-inflammatory drug, has been synthesized. The drug and complexes have been characterized by elemental and thermogravimetric (TG) analysis, Fourier transform (FT)-IR, ¹H-NMR, ¹³C-NMR, UV-Vis spectroscopy and magnetic susceptibility measurements. The (pseudo)octahedral geometry has been proposed for all complexes based on electronic spectra and magnetic moments. With exception of the Cu(II) complex, where bridging bidentate mode of COO groups has been found, FT-IR spectra confirmed chelately coordinated COO groups in the other complexes. The general formula of the complexes is [M(H₂O)₂(oxa) ₂] · xH₂O, with x=2 for M=Mn, Co and Ni and x=1.5 for Zn. The binuclear Cu(II) complex, [Cu₂(H₂O) ₂(OH)(oxa)₃]·2H₂O, has strong Cu-Cu interactions of antiferromagnetic type. The complexes and Hoxa did not exhibit the cytotoxic effect to peritoneal macrophages. For the first time these complexes have been tested for their in vitro antiproliferative activity against human colon and breast cancer cell lines, HCT-116 and MDA-231, respectively. For all investigated compounds significant antiproliferative effects have been observed. Ni(II) complex has been shown to be a promising antiproliferative agent exerting excellent activity against HCT-116 even in nanomolar concentrations.

Full text of DOI:10.1248/cpb.c12-00185

July 2012
Regular Article
Chem. Pharm. Bull. 60(7) 865–869 (2012)
865
Synthesis, Characterization and Antiproliferative Activity of Transition
Metal Complexes with 3-(4,5-Diphenyl-1,3-oxazol-2-yl)propanoic Acid
(Oxaprozin)
Bojan DJ Božić,a Jelena R Rogan,a Dejan D Poleti,a Nemanja P Trišović,a Biljana DJ Božić,b and
,a
Gordana S Ušćumlić*
b
a Faculty of Technology and Metallurgy, University of Belgrade; Karnegijeva 4, 11000 Belgrade, Serbia: and Faculty
of Biology, University of Belgrade; Studentski trg 3, 11000 Belgrade, Serbia.
Received February 22, 2012; accepted April 12, 2012
A series of novel Mn(II), Co(II), Ni(II), Cu(II) and Zn(II) complexes with oxaprozin (Hoxa), a non-
steroidal anti-inflammatory drug, has been synthesized. The drug and complexes have been character-
ized by elemental and thermogravimetric (TG) analysis, Fourier transform (FT)-IR, 1H-NMR, 13C-NMR,
UV-Vis spectroscopy and magnetic susceptibility measurements. The (pseudo)octahedral geometry has
been proposed for all complexes based on electronic spectra and magnetic moments. With exception of
the Cu(II) complex, where bridging bidentate mode of COO groups has been found, FT-IR spectra con-
firmed chelately coordinated COO groups in the other complexes. The general formula of the complexes is
[M(H2O)2(oxa)2]·xH2O, with x=2 for M=Mn, Co and Ni and x=1.5 for Zn. The binuclear Cu(II) complex,
[Cu2(H2O)2(OH)(oxa)3]·2H2O, has strong Cu–Cu interactions of antiferromagnetic type. The complexes and
Hoxa did not exhibit the cytotoxic effect to peritoneal macrophages. For the first time these complexes have
been tested for their in vitro antiproliferative activity against human colon and breast cancer cell lines,
HCT-116 and MDA-231, respectively. For all investigated compounds significant antiproliferative effects have
been observed. Ni(II) complex has been shown to be a promising antiproliferative agent exerting excellent
activity against HCT-116 even in nanomolar concentrations.
Key words oxaprozin; transition metal complex; antiferromagnetic interaction; cytotoxic effect; antiprolif-
erative activity
Oxaprozin (3-(4,5-diphenyl-1,3-oxazol-2-yl)propanoic acid), with ketoprofen [(R,S)-2-(3-benzoylphenyl)propanoic acid]
Hoxa, belongs to the class of non-steroidal anti-inflammatory has exhibited enhanced antiproliferative effects on human
drugs (NSAIDs) with analgesic and antipyretic properties.1) breast cancer cell line T47D rich in progesterone receptors.24)
Its therapeutic effects result from a selective inhibition of the The radical scavenging activity of Hoxa is synergistically
enzyme cyclooxygenase-2 (COX-2), which is largely respon- enhanced upon Cu(II) coordination in [Cu2(DMSO)2(oxa)4].25)
sible for the production of prostaglandins in most pathological All this facts indicate that TM complexes with oxa− ligand
states.2) Epidemiological studies have indicated that continu- might exhibit additional biological activities and encouraged
ous therapy with NSAIDs make real promise of chemopreven- us to carry out a study of their antiproliferative activity.
tion and adjunct therapy for cancer patients.3,4) It has been
In this study, five new oxa TM complexes containing
demonstrated that COX-2 overexpression is involved in the Mn(II), Co(II), Ni(II), Cu(II) and Zn(II) ions were synthesized
invasion and growth of cancer,5) and blockade of COX-2 func- and characterized. The complexes, as well as Hoxa were also
tion by corresponding drugs can reduce cancer progression in tested in vitro against human colon and breast cancer cell
experimental models.6,7) On the other hand, beneficial effects lines, HCT-116 and MDA-231, respectively, by 3-(4,5-dimeth-
of NSAIDs can be additionally explained by an independent ylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay.
mechanism of action in relation to the COX-inhibition path-
way.8) COX-independent effects of NSAIDs are mediated
Experimental
through modulation of activity of various intracellular kinas-
General Procedure The starting materials were obtained
es, e.g. extracellular signal-regulated kinase (ERK), AkT, p38 from Aldrich and Fluka, and were used without further puri-
mitogen activated protein kinase (MAPK), c-Jun N-terminal fication.
kinase (JNK),9–12) which can lead to the change in activity and
All the investigated compounds were synthesized following
expression of some transcription factors (e.g. nuclear factor the procedure presented in the synthetic scheme (Chart 1). In
(NF)-κB, Erg-1, AP-1, p-53, PPARγ) inducing apoptosis.13–16)
detail, oxaprozin, Hoxa, (2.0mmol) was added to the aqueous
The first row transition metal (TM) ions have attracted solution containing 2.0mmol of NaOH in 50mL H2O. This
°
significant attention, because they represent trace element that solution was continuously stirred at 40 C for 2h, while a clear
occurs in the reactive centers of many enzymes.17–21) It has solution of Naoxa was formed. Then a solution of Naoxa was
been demonstrated that TM complexes of NSAIDs are more added dropwise at room temperature in aqueous M(NO3)2 so-
active than their parent drugs and exhibit lower side-effects.22) lution (9.0mL of 0.1M; 0.9mmol), M=Mn(II), Co(II), Ni(II),
Thus, some TM complexes with naproxen [(+)-(S)-2-(6- Cu(II) and Zn(II), under violent stirring for 1h. Immediately
methoxynaphthalen-2-yl)propanoic acid], express significant formed precipitate was filtered off after standing overnight,
anti-inflammatory effect.23) A square planar Cu(II) complex washed several times with distilled water and absolute ethanol
and dried in a vacuum at room temperature.
The elemental analysis of the Hoxa and its complexes were
The authors declare no conflict of interest.
*To whom correspondence should be addressed. e-mail: goca@tmf.bg.ac.rs
© 2012 The Pharmaceutical Society of Japan

866
Vol. 60, No. 7
Chart 1. Synthesis of Hoxa and TM Complexes, Where M=Mn (1), Co (2), Ni (3), Cu (4), Zn (5); x=4 for 1–3, x=3.5 for 5)
carried out by standard analytical micromethods using an HCT-116 were incubated without and with 0.001, 0.01, 0.1, 1,
Elemental Vario EL III microanalyzer. Total content of water 10 and 50µM concentrations of the investigated compounds
of crystallization was determined by thermogravimetric (TG) and MDA-231 cells were incubated without and with 0.01, 1
°
analysis performed from room temperature up to 300 C on and 50µM concentrations of the investigated compounds. Un-
an SDT Q600 TGA/DSC instrument (TA Instruments) with treated HCT-116 and MDA-231 cells were cultivated only in
−1
°
heating rate of 20 Cmin in a dry nitrogen atmosphere (flow medium for cultivation without investigated compounds and
rate of 100cm3 min−1). The H- and 13C-NMR spectral mea- used as a control. After treatment with the investigated com-
1
surement of Hoxa was performed on a Bruker AC 250 spec- pounds during 48h cell proliferation was determined by MTT
1
trometer at 200MHz for H-NMR and 50MHz for 13C-NMR assay. This test is based on the color reaction of mitochondrial
spectra. The spectrum was recorded at room temperature in dehydrogenase from living cells with MTT. Briefly, 10µL of
DMSO-d6. The chemical shifts are expressed in ppm values MTT solution (5mgmL−1) was added to each well after cells
1
referenced to TMS (δH=0ppm) in H-NMR spectra, and the treatment during 48h and cells incubate for an additional
residual solvent signal (δC=39.5ppm) in 13C-NMR spectra. 3h at 37 C. Produced formazan was dissolved by overnight
°
FT-IR spectra in the 4000–400cm−1 range were recorded on a incubation with sodium dodecyl sulfate (SDS)-HCl mixture
Bomem MB 100 FT-IR spectrophotometer in the form of KBr (10% SDS in 0.01N HCl) and absorbance was measured at
pellets. The electronic spectra of the complexes were recorded dual wavelength of 570/650nm with an enzyme-linked immu-
by solution techniques using dimethyl sulfoxide (DMSO) as a nosorbent assay (ELISA) 96-well plate reader. The percentage
solvent with Shimadzu 1700 spectrophotometer. Magnetic sus- of viable cells was calculated as the ratio between absorbance
ceptibility measurements were made at room temperature us- at each dose of the compounds and absorbance of untreated
ing an MSB-MK1 magnetic susceptibility balance (Sherwood control cells ×100, and regarding the percentage of viable
Scientific Ltd., Cambridge, U.K.). The data were corrected for cells, the percent inhibition of cells proliferation was then
diamagnetic susceptibilities.
calculated.
The Cytotoxic Effect and Antiproliferative in Vitro
Characterization Oxaprozin (Hoxa): White solid, yield
Screening The synthesized Hoxa and its metal complexes 72%, Anal. Calcd for C18H15NO3 (%): C, 73.71; H, 5.15;
were evaluated for their cytotoxic effects to rat peritoneal N, 4.78. Found (%): C, 73.70; H, 5.36; N, 4.90. 1H-NMR
macrophages by MTT assay.
(DMSO-d6): 12.36 (s, 1H, O–H), 7.30–7.59 (m, 10H, 2Ph-H),
Further, the investigated compounds for antiproliferative 3.06 (t, 2H, J=6.6Hz, CH2CH2CO2H), 2.79 (t, 2H, J=7Hz,
effect to human colon and breast cancer cell lines, HCT-116 CH2CH2CO2H); 13C-NMR (DMSO-d6): 173.5 (C1), 162.7 (C4),
and MDA-231, respectively, by MTT assay were evaluated. 144.9 (C5), 134.6 (C12), 132.3 (C13), 129.2 (C15, C17), 129.1
The antiproliferative effect of these drugs was expressed as a (C6), 128.9 (C8, C10), 128.7 (C16), 128.4 (C10), 127.7 (C14,
percentage of inhibition of untreated cells proliferation. The C18), 126.6 (C7, C11), 30.5 (C2), 23.2 (C3). Selected FT-IR
HCT-116 and MDA-231 cells were mainted in Dulbecco s data (KBr) cm−1: 3034 [ν(CH)], 2930 [ν(CH)], 2611 [ν(CH2)],
’
’
modified Eagle s medium supplemented with 10% fetal bo- 1720 [ν(C=O)], 1568 [ν(CC)], 1502 [ν(CC)], 1443 [δ(CO),
vine serum. Cells were grown in culture bottles supplied with δ(CH2)], 1362 [ω(CH), ν(CC)], 1275 [ω(CH2), δ(COH)], 1060
medium for cultivation, and after a few passages cells were [δ(CCC), ω(CH)], 965 [τ(HCCH)], 922 [γ(OHO)], 757 [δ(CH2),
seeded in 96-well plate. Cells were cultured in a humidified γ(COC)], 586 [τ(CCOH), γ(O=COH)], 524 [γ(CC)].
°
atmosphere of 5% CO2 at 37 C during 24h. The next 48h the
[Mn(H2O)2(oxa)2]·2H2O (1): White solid, yield 62%, Anal.

July 2012
867
Calcd for C36H36MnN2O10 (%): C, 60.76; H, 5.10; N, 3.94. complexes are referred to by the corresponding numbers in
Found (%): C, 60.53; H, 5.10; N, 3.97. Selected FT-IR data Table 1 hereinafter.
(KBr) cm−1: 3294 [ν(OH)], 3058 [ν(CH)], 2943 [ν(CH)], 1566
With the exception of 1, which was dehydrated in a single
[νas(COO)], 1549 [νas(COO)], 1447 [νs(COO)], 1431 [νs(COO)], step process, the results of TG analysis also allowed to distin-
760 [δ(CH2), γ(COC)], 696 [δ(CH), γ(CH)], 443 [ν(MnO)]. guish between coordinated and uncoordinated H2O molecules.
[Co(H2O)2(oxa)2]·2H2O (2): Pink solid, yield 57%, Anal. Complexes 2–4 were dehydrated in two overlapped steps
Calcd for C36H36CoN2O10 (%): C, 60.42; H, 5.07; N, 3.92. (Table 1) showing nearly equal mass loss in both steps. Com-
Found (%): C, 60.32; H, 4.94; N, 3.94. Selected FT-IR data plex 5 was dehydrated in two fairly separated steps: the first
(KBr) cm−1: 3381 [ν(OH)], 3277 [ν(OH)], 3031 [ν(CH)], 2949 step up to 77.8 C can be attributed to the removal of 1.5H2O
°
[ν(CH)], 1568 [νas(COO)], 1549 [νas(COO)], 1502 [ν(CC)], 1446 molecules, whereas the remaining 2H2O molecules were
°
[νs(COO)], 1414 [νs(COO)], 760 [δ(CH2), γ(COC)], 696 [δ(CH), eliminated in the subsequent step up to 200.1 C. These obser-
γ(CH)], 675 [δ(CCC)], 445 [ν(CoO)]. UV-Vis spectrum (nm): vations, together with temperature ranges of dehydration and
478, 510, 560, 621.
positions of differential thermalgravimetric (DTG) maxima
[Ni(H2O)2(oxa)2]·2H2O (3): Light blue solid, yield 79%, (Table 1) show that the difference between binding energy
Anal. Calcd for C36H36N2NiO10 (%): C, 60.44; H, 5.07; N, 3.92. of coordinated and uncoordinated H2O molecules generally
Found (%): C, 60.22; H, 5.06; N, 3.91. Selected FT-IR data increases, while the overall energy required for total dehydra-
(KBr) cm−1: 3389 [ν(OH)], 3277 [ν(OH)], 3032 [ν(CH)], 2951 tion of the complexes approximately decreases in the order
[ν(CH)], 1568 [νas(COO)], 1545 [νas(COO)], 1502 [ν(CC)], 1444 Co–Ni–Cu–Zn, i.e. both properties follow the order of TMs in
[νs(COO)], 1414 [νs(COO)], 760 [δ(CH2), γ(COC)], 696 [δ(CH), the Periodic table. Again, the exception is the complex 1.
γ(CH)], 675 [δ(CCC)], 447 [ν(NiO)]. UV-Vis spectrum (nm):
422, 714, 790.
FT-IR spectrum of Hoxa is in agreement with the lit-
erature.27) In the spectra of 1–5 a new weak band that can
[Cu2(H2O)2(OH)(oxa)3]·2H2O (4): Blue solid, yield 72%, be attributed to the M–O stretching vibrations appeared in
Anal. Calcd for C54H51Cu2N3O4 (%): C, 59.33; H, 4.70; N, 3.84. the range 450–440cm−1 and this band verifies oxa− coordina-
Found (%): C, 59.05; H, 5.00; N, 3.88. Selected FT-IR data tion as O,O-donor ligand.23) ν(OH) stretching vibrations were
(KBr) cm−1: 3420 [ν(OH)], 3057 [ν(CH)], 2924 [ν(CH)], 1628 found as very broad bands in the 3450–3250cm−1 region con-
[νas(COO)], 1614 [νas(COO)], 1570 [ν(CC)], 1437 [νs(COO)], 764 firming the presence of coordinated and uncoordinated water
[δ(CH2), γ(COC)], 694 [δ(CH), γ(CH)], 443 [ν(CuO)]. UV-Vis molecules. Except for 4, FT-IR spectra of other complexes are
spectrum (nm): 721.
almost identical indicating a great structural similarity.
[Zn(H2O)2(oxa)2]·1.5H2O (5): White solid, yield 65%, Anal.
The most prominent feature in the FT-IR spectra of 1–5
Calcd for C36H35N2O9.5Zn (%): C, 60.64; H, 4.95; N, 3.93. was the existence of two strong bands originating from the
Found (%): C, 60.5; H, 4.92; N, 3.94. Selected FT-IR data coordinated carboxylate groups [νas(COO) and νs(COO)] in
(KBr) cm−1: 3383 [ν(OH)], 3275 [ν(OH)], 3057 [ν(CH)], 2949 the 1650 to 1420cm−1 region (Table 1) . It is well-known that
Δ
[ν(CH)], 1568 [νas(COO)], 1547 [νas(COO)], 1444 [νs(COO)], positions of these bands and their difference ( ν) are useful
1414 [νs(COO)], 762 [δ(CH2), γ(COC)], 696 [δ(CH), γ(CH)], 445 tool to predict the coordination mode of COO groups.28,29) The
Δ
[ν(ZnO)].
ν values for the complexes (Table 1) were compared to the
−1
Δ
corresponding value ( νi=144cm ) for purely ionic Naoxa
salt, which was prepared by neutralization of Hoxa. The
Δ
ν
Results and Discussion
Synthesis, Characterization and Structural Formulae of value of 4 is higher than that of Naoxa indicating monodentate
the Complexes Oxaprozin was prepared according to the or asymmetric bridging bidentate coordination mode of COO
literature procedure26) (Chart 1) and characterized by elemen- groups, whereas the ν values of 1–3 and 5 are lower than νi
Δ
Δ
1
tal analysis, H-NMR, 13C-NMR and FT-IR spectroscopy. All and correspond to the chelating coordination modes.
complexes were prepared by the ligand exchange reaction in
aqueous solution (Chart 1) and characterized by elemental and tion T1g(F)
TG analysis, FT-IR, UV-Vis spectroscopy and magnetic sus- Co(II) complexes, was present at 478nm. The band corre-
ceptibility measurements. sponding to the forbidden two-electron transition appeared
The formulae of the complexes 1–5 based on analytical as a shoulder at 621nm. It was also possible to notice a spin-
In the electronic spectrum of 2, the highest energy transi-
4
→
4T1g(P), characteristic for distorted octahedral
4
and spectral data, TG analysis and assumption that coordi- allowed transition assigned to T1g(F)→
4A2g(F) at 560nm and
nation number of all TM ions is 6 are listed in Table 1. The one more spin forbidden transition at 510nm originated in
Table 1. Structural Formulae, TG Data, Selected FT-IR Data and Magnetic Moments of the Complexes 1–5
TG analysis
Δ
νas(COO)
νs(COO)
ν(COO)
μeff
(BM)
Total H2O content, found
(calcd) (%), and temperature
No.
Complex
(cm−1
)
(cm−1
)
(cm−1
)
DTG maxima
°
( C)
°
range of dehydration ( C)
1
2
3
4
5
[Mn(H2O)2(oxa)2]·2H2O
[Co(H2O)2(oxa)2]·2H2O
[Ni(H2O)2(oxa)2]·2H2O
[Cu2(H2O)2(OH)(oxa)3]·2H2O
[Zn(H2O)2(oxa)2]·1.5H2O
9.7 (10.1), 30.0–140.6
9.4 (10.1), 45.1–193.4
10.2 (10.1), 33.3–158.6
6.6 (6.6), 25.0–118.1
8.3 (8.8), 29.9–200.1
103.9
1557
1557
1556
1621
1556
1431
1430
1427
1437
1429
126
127
129
184
127
5.82
4.70
3.08
1.40
—
107.2, 131.0
72.8, 113.6
64.8, 90.5
56.8, 99.8

868
Vol. 60, No. 7
Fig. 1. Proposed Structures of the Complexes 1–5 (M=Mn, Co, Ni, Zn;
x=2 for 1–3 and x=1.5 for 5)
ROO represents an oxa− ligand.
3
the 2G state.30) For 3, three absorption bands: A2g
→
3T1g(P),
3
3A2g
→
3T1g(F) and A2g
→
3T2g were observed at 422, 714 and
790nm, respectively, also supporting distorted octahedral
geometry.30) In the electronic spectrum of 4, a moderately
strong, broad and asymmetric absorption band at 721nm was
found. The position of this band indicates the O6 chromophore
with D2 or C2ν symmetry.30) In general, the UV-Vis spectra of
Fig. 2. The Antiproliferative Effect of Hoxa and 1–5 on HCT-116 Cell
Line at Concentration of 0.001µM
*p<0.05; **p<0.01 vs. nontreated cells.
2–4 are in accordance with (pseudo)octahedral geometry of increased concentration. Thus, Hoxa in the 0.1, 1 and 10µM
the metal site. concentration and 4 in the 1, 10 and 50µM have statistically
The magnetic moment of 4 (1.40 BM) was considerably significant inhibitory potency. The inhibitory potency of 5 to
lower than spin-only value (1.73 BM31)) demonstrating strong HCT-116 cells proliferation is significant only in 0.1 and 50µM.
antiferromagnetic exchange interactions between the neigh- On the contrary, complexes 1–3 showed excellent inhibition of
boring Cu(II) ions. A nearly identical value was also obtained HCT-116 cells proliferation in the whole concentration range.
by Dutta and co-workers for a very similar binuclear Cu(II) The best values of percentage of inhibition were expressed by
complex with formula [Cu2(DMSO)2(oxa)4] and very short 3 (Fig. 2). These results indicate a very potent antiproliferative
Cu–Cu distance of 2.61Å.25) Therefore, an analogous dimeric potency of 3 in the lowest concentration (0.001µM) and it will
formula (Table 1) and magnetic interactions are expected for be the base for future studies.
4. Complexes 1–3 are high-spin and the corresponding μeff
The results of inhibitory activity of Hoxa and 1–5 on the
values (Table 1) are characteristic for (pseudo)octahedral coor- other tumor cell line, MDA-231 are also shown in Table 2.
dination geometry of central TM ions.31) In conclusion, colors, It is evident that 2 and 5 in the highest investigated concen-
electronic spectra and magnetic moments unambiguously con- tration and 5 in the lowest concentration exhibit inhibitory
firm octahedral or distorted octahedral coordination geometry effect on MDA-231 cells proliferation. Hoxa, as well as 1, 3
of all complexes, as shown in Fig. 1.
and 4 demonstrated statistically significant potent capacity of
Inhibition of Cancer Cell Proliferation The synthesized inhibition of MDA-231 cells proliferation in all investigated
compounds were evaluated for inhibition of proliferation concentrations.
of human colon and breast cancer cell lines, HCT-116 and
Presented results of antiproliferative activity of the inves-
MDA-231, respectively. The cell proliferation was determined tigated complexes at lower concentrations are in agreement
by MTT assay after 48h of treatment with Hoxa and 1–5 in with the literature data23–25) about increased biological activi-
the 0.001–50µM range of concentration.
ties of TM complexes of NSAIDs in comparison to the activ-
Investigation of antiproliferative activities of Hoxa and 4 on ity of their parent drugs. Especially, an improved antiprolifera-
HCT-116 cell line (Table 2) showed an increased activity with tive activity of 1 and 3 against HCT-116, as well as of 1, 3 and
Table 2. The Antiproliferative Effect of Hoxa and 1–5 on HCT-116 and MDA-231 Cell Lines
Inhibition of HCT-116 cells proliferation (%)
Concentration (µM)
Hoxa
1
2
3
4
5
0.001
0.01
0.1
2.9 0.4
17.4 0.4**
12.7 0.8**
13.7 0.3**
12.8 0.6*
17.2 0.3**
2.9 0.4
10.0 0.5*
13.5 0.7*
8.9 0.4*
9.6 0.4*
9.9 0.4*
18.6 0.9*
45.3 0.9**
7.1 0.5*
0.9 0.7
1.3 1.4
2.0 2.9
1.1 2.25
14.4 0.68*
0.8 1.4
1.0 1.2
15.5 0.9*
32.1 0.7**
52.7 0.8**
19.5 0.2**
14.6 0.3**
27.8 1.1*
38.1 0.7**
2.6 1.1
1
9.4 0.3*
15.1 0.6*
25.4 0.4**
10
50
0.9 0.4
a)
—
18.6 0.4**
Inhibition of MDA-231 cells proliferation (%)
0.01
15.7 0.5**
42.9 0.4**
22.8 0.2**
26.7 0.6*
65.6 0.2**
4.5 0.8
17.8 0.2*
19.2 0.2*
60.5 0.2**
19.9 0.1**
19.6 0.4*
16.5 0.5*
13.1 0.4
1
12.1 0.5
a)
—
50
61.4 0.1***
52.8 0.3***
41.8 0.2***
*p<0.05; **p<0.01; ***p<0.001 vs. nontreated cells. a) This concentration can not be measured due to limited solubility of Hoxa in the medium for cell cultivation.

July 2012
869
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4 against MDA-231 cancer cell lines has shown (Table 2).
Dose-dependent antiproliferative effects to HCT-116 cell
line were observed for Hoxa and 4. However, dose-dependent
effects were not found for 1–3, but these compounds showed
good antiproliferative activity in all investigated concentra-
tions (excluding 1 in the highest concentration). Such unex-
pected antiproliferative activity of 1–3 can be explained with
different type of induced cell death (apoptosis and necrosis) of
treated cells and various mechanisms of apoptosis.6–8) Further,
with exception of 2 and 5, dose-dependent antiproliferative ef-
fects to MDA-231 cell line for other investigated compounds
were also found.
The complex 5 showed inhibitory potency to HCT-116 cells
only at the concentrations of 0.1 and 50µM, and to MDA-231
cells only at the concentrations of 0.01 and 50µM. A plausible
explanation for diverse inhibitory potency of 5 in comparison
to other compounds could be different modes of action of 5 at
low and high concentration. It could be assumed that in low
concentration 5 has a similar satisfactory effect as all other
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lease of high amounts of Zn(II) ions in culture medium could
16) Ho C. C., Yang X. W., Lee T. L., Liao P. H., Yang S. H., Tsai C. H.,
Chou M. Y., Eur. J. Clin. Invest., 33, 875–882 (2003).
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induce rapid uptake of these ions by the cells and promote a
caspase-independent alternative apoptosis pathway.32)
For confirmation of antiproliferative effects of Hoxa and
“
”
18) Lippard S. J., Berg J. M., Principles of Bioinorganic Chemistry,
University Science Books, Mill Valley, 1994, p. 411.
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1–5 an additional examination of cytotoxic effect (non-specific
cells killing) to viability of unstimulated and lipopolysaharide
(LPS) stimulated rat peritoneal macrophages by MTT assay
was conducted. This part of the study demonstrated that Hoxa
and 1–5 did not exhibit the cytotoxic effect to peritoneal mac-
rophage (data not shown), which is well-known cell used for
this type of investigation.
“
20) Stipanuk M. H., Biochemical, Physiological & Molecular Aspects
”
of Human Nutrition, 2nd ed., W. B. Saunders Company, New York,
2006, pp. 1043–1067.
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Conclusion
Oxaprozin and its complexes with Mn(II), Co(II), Ni(II),
Cu(II) and Zn(II) were synthesized and characterized. A dis-
torted octahedral geometry was proposed for all complexes.
All complexes exhibited significant antiproliferative activity
against human colon and breast cancer cell lines, HCT-116 and
MDA-231, respectively. Especially, Ni complex showed very
potent antiproliferative effect on HCT-116 cell line at concen-
tration of 0.001µM with inhibition of 45.3 0.9%.
28) Deacon G. B., Phillips R., Coord. Chem. Rev., 33, 227–250 (1980).
“
29) Nakamoto K., Infrared and Raman Spectra of Inorganic and Coor-
Acknowledgements The authors acknowledge the finan-
cial support of the Ministry of Education and Science of the
Republic of Serbia (Grants No. 172013 and III45007).
dination Compounds, Part B, Applications in Coordination, Organo-
metallic and Bioinorganic Chemistry, 5th ed., John Wiley & Sons,
New York, 1997, pp. 59–62.
”
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