Antiproliferative Activity of Gold(I) N-Heterocyclic Carbene and Triphenylphosphine Complexes with Ibuprofen Derivatives as Effective Enzyme Inhibitors

Article abstract of DOI:10.1002/aoc.5618

A series of gold(I) complexes of ligand ibuprofen-alkynyl (but-3-yn-1-yl 2-(4-isobutylphenyl)propanoate, LE) with N-heterocyclic carbene (LC: 1,3-dimethylimidazol-2-ylidene) and triphenylphosphine (PPh₃) ligands with formula (LE)Au (LC) (comple

Full text of DOI:10.1002/aoc.5618

Received: 25 November 2019
DOI: 10.1002/aoc.5618
Revised: 13 February 2020
Accepted: 15 February 2020
F U L L P A P E R
Antiproliferative Activity of Gold(I) N-Heterocyclic Carbene
and Triphenylphosphine Complexes with Ibuprofen
Derivatives as Effective Enzyme Inhibitors
Leila Tabrizi1
| Julia Romanova2
1School of Chemistry, National University
of Ireland, Galway, University Road,
Galway, H91 TK33, Ireland
2Faculty of Chemistry and Pharmacy,
Department of Inorganic Chemistry,
University of Sofia “St. Kliment Ohridski”,
1 James Bourchier Blvd., Sofia, 1164,
Bulgaria
A series of gold(I) complexes of ligand ibuprofen-alkynyl (but-3-yn-1-yl
2-(4-isobutylphenyl)propanoate, LE) with N-heterocyclic carbene (LC:
1,3-dimethylimidazol-2-ylidene) and triphenylphosphine (PPh3) ligands with
formula (LE)Au (LC) (complex 1) and (LE)Au (PPh3) (complex 2) were synthe-
sized and fully characterized by spectroscopic methods. In order to reveal the
cytotoxicity mechanism, the interaction of complex 1 or 2 with cysteine (HCys)
has been studied by experimental and density functional theory (DFT)
methods. The compounds were investigated for their anticancer activity
against MCF-7, MDAMB 231 breast cancer cells, HT-29 colon cancer cells and
MCF-10A non-tumor breast cell line. The results were compared with cisplatin
and auranofin as reference drugs. The complex 2 showed more cytotoxic activ-
ity than complex 1. The complex 2 was 4.2, 3.7, and 1.7 fold more active than
cisplatin against HT-29, MDA-MB-231, MCF-7 cancer cell lines, respectively.
The inhibition of thioredoxin reductase of complexes 1 and 2 including cyto-
solic (TrxR1) and mitochondrial (TrxR2) thioredoxin reductase and also the
inhibition of glutathione reductase (GR) were studied in detail. Moreover, the
cellular uptake and reactive oxygen species (ROS) generation of compounds
were investigated. Based on the DFT calculations a relationship between the
σ-donor ability of the isolated ligands and cytotoxicity is suggested.
Correspondence
Leila Tabrizi, School of Chemistry,
National University of Ireland, Galway,
University Road. Galway, H91 TK33,
Ireland.
Email: leila.tabrizi@nuigalway.ie
Julia Romanova, Faculty of Chemistry
and Pharmacy, Department of Inorganic
Chemistry, University of Sofia “St.
Kliment Ohridski”, 1 James Bourchier
Blvd., Sofia 1164, Bulgaria.
Email: jromanova@chem.uni-sofia.bg
K E Y W O R D S
cytotoxicity, gold(I) complex, ibuprofen, interaction cysteine, Thioredoxin reductase
1 | INTRODUCTION
cellular uptake and pharmacokinetic properties.[5–12]
Recently, the N-heterocyclic carbenes (NHCs) has been
Since the success of cisplatin as tumor chemotherapy
drug, the research on metallodrugs for anticancer therapy
has been developed during the last decades.[1,2] More-
over, the discovery of auranofin as an antirheumatic
agent has been triggered the developing of the gold com-
plexes for anticancer drugs in vitro and in vivo.[3,4]
developed as substitutes to phosphines as ligands for
gold(I) complexes. The interest in gold NHC complexes
as anticancer drugs is caused by a number of discoveries
such as the great cytotoxic properties, induction of apo-
ptosis, and inhibition of enzyme thioredoxin reductase
(TrxR).[13–26]
Gold phosphine complexes are omnipresent in gold
chemistry and have considerable influence in designing
of anticancer drug due to their roles in lipophilicity for
The anticancer properties of non-steroidal anti-
inflammatry drugs (NSAIDs) such as indomethacin,
naproxen, aspirin, and ibuprofen have been reported
Appl Organometal Chem. 2020;e5618.
wileyonlinelibrary.com/journal/aoc
© 2020 John Wiley & Sons, Ltd.
1 of 10
https://doi.org/10.1002/aoc.5618

2 of 10
TABRIZI AND ROMANOVA
against colorectal, colon, breast and pancreatic cancers in
the literature.[27–32] The complexation with different
metals has enhanced the biological activity as anticancer
agents.[27] Ibuprofen is one of the most common NSAIDs
used in the clinics for the treatment of headache, muscu-
lar ache, arthritis rheumatoid, fever and pain related to
tissue inflammation.[33] There are reports of silver(I),
gold(I), and zinc (II) complexes with ibuprofen for
antibacterial activities. Also, a platinum (II)/(IV), Ru (II),
Cu (II) complexes with ibuprofen have been reported as
anticancer drugs.[27,34–40] Recently, we also have reported
the antioxidant activity of copper (II) complexes of
ibuprofen amide-phenanthroline and cyclometalated
ruthenium (II) complex containing ibuprofen for inhibi-
tion of cyclooxygenase and in vitro cytotoxicity activi-
ties.[41,42] However, no organometallic gold(I) complexes
with ligand ibuprofen coupled alkynyl group seems to be
reported so far.
properties of the synthesized complexes have been stud-
ied towards a wide range of cancer cells, and the enzyme
inhibitors including the inhibition of TrxR and of the
enzyme glutathione reductase (GR) of complexes were
investigated in details. DFT results suggest dependence
between the σ-donor ability of the isolated PPh3 and LC
ligands and the measured cytotoxicity.
2 | EXPERIMENTAL
2.1 | Materials and instruments
All chemicals were obtained from commercial sources
unless otherwise stated. Au (PPh3)Cl (PPh3:
triphenylphosphine)[43]
and
[Au
(LC)Cl]
(LC:
1,3-dimethylimidazol-2-ylidene)[44] were synthesized as
1
previously reported. H, 13C and 31P NMR spectra were
Herein, we report the synthesis and characterization
of the ligand ibuprofen-alkynyl (LE) and its gold(I)
complexes containing N-heterocyclic carbene (LC:
1,3-dimethylimidazol-2-ylidene) and triphenylphosphine
(PPh3) ligands with formula (LE)Au (LC) (complex 1)
and (LE)Au (PPh3) (complex 2) (Figure 1). In order to
reveal the cytotoxicity mechanism, the interactions of
gold(I) complexes 1 and 2 with cysteine, the product of
which is (LE)Au (HCys) (complex 3), have been experi-
mentally studied and compared with density functional
theory (DFT) results. The structure of all reactants and
products in the ligand exchange reaction with HCys has
been optimized and the free energy of the later was theo-
retically estimated at DFT level. The anticancer
recorded on a 400 Mercury Plus Varian instrument oper-
1
ating (400 MHz for H and 100 MHz for 13C relative to
TMS, and 162 MHz relative to 85% H3PO4) at ambient
temperature in DMSO-d6. Elemental analyses were per-
formed with an EA 3000 CHNS. ESI mass spectra were
recorded on a Waters LCT Premier XE spectrometer.
2.2 | Synthesis of the ligand but-3-yn-1-yl
2-(4-isobutylphenyl)propanoate (LE)
To ibuprofen (206 mg, 1 mmol) in dry dichloromethane
(7 ml) was added oxalyl chloride (171 μL, 2 mmol) and
DMF (3 drop). The solution was stirred at room tempera-
ture for 100 min, and evaporated in rotavap. The
resulting compound was dissolved in dry THF (8 ml) and
added the 3-Butyn-1-ol (91 μL, 1.2 mmol) and
triethylamine (697 μL, 5 mmol) in dry THF (8 ml) at
ꢀ
0 C. After 15 min., the resulting solution was stirred at
room temperature for 6 hr and evaporated in the rotavap.
The resulting compound was dissolved in ethyl acetate
(20 ml), washed with brine (2 × 10 ml), and dried over
MgSO4 and finally concentrated in rotavap. The silica gel
column chromatography was used to purify the crude
compound by ethyl acetate: petroleum ether (2: 8) as
mobile phase. White solids (164.5 mg, 63.74% yield, and
1 mmol). Anal. Calc. (%) for C17H22O2 (258.1620): C,
79.03; H, 8.58; Found (%): C, 78.97; H, 8.56. TOF-MS:
+
1
259.1698 [M + H] . H NMR (DMSO-d6): δ 7.20 (d, 2H,
H-5, J = 7.6 Hz), 7.05 (d, 2H, H-4, J = 7.6 Hz), 4.25 (t,
2H, H-8, J = 7.2 Hz), 3.83 (q, 1H, H-6, J = 7.6 Hz), 2.89
(s, 1H, H-11), 2.36 (d, 2H, H-3, J = 7.6 Hz), 2.22 (t, 2H, H-
9, J = 7.2 Hz), 1.85–1.90 (m, 1H, H-2), 1.63 (d, 3H, H-7,
J = 7.6 Hz), 0.93 (d, 6H, H-1, J = 7.6 Hz). 13C NMR
(DMSO-d6): δ 174.4 (C=O), 142.1 (Ar), 135.0 (Ar), 130.3
FIGURE 1 Structures of the ligand and the gold complexes
(1 and 2) and the product of their interaction with cysteine (3) used
in this investigation

GOLD(I) N-HETEROCYCLIC CARBENE AND TRIPHENYLPHOSPHINE COMPLEXES
3 of 10
(Ar), 129.2 (Ar), 79.9 (C10), 70.0 (C11), 61.8 (C8), 45.1
(C3), 37.2 (C6), 30.0 (C2), 23.3 (C9), 19.9 (C1), 12.0 (C7).
2.5 | Interaction of complexes 1 and
2 with cysteine (HCys): Synthesis of
complex (LE)au (HCys), 3
Complex 1 (55 mg, 0.1 mmol) or 2 (71.6 mg, 0.1 mmol)
and cysteine (36.3 mg, 0.3 mmol) were dissolved in 5 ml
DMF and stirred at room temperature for 24 hr. Then,
the unreacted cysteine was removed by filtration. The
solution was rotary-evaporated to dryness to give the
crude product. The residue was dissolved in acetonitrile
(5 ml) and n-hexane (20 ml) was added to produce the
precipitation of yellow solid. Yellow solid (33 mg, 57.31%
yield, and 0.1 mmol). Anal. Calc. (%) for C20H28AuNO4S
(575.1405): C, 41.74; H, 4.90; N, 2.43; Found (%): C,
41.71; H, 4.88; N, 2.40. TOF-MS: 576.1483 [M + H] . H
NMR (DMSO-d6): δ 7.22 (d, 2H, H-5, J = 7.6 Hz), 7.10 (d,
2H, H-4, J = 7.6 Hz), 4.31 (t, 2H, H-8, J = 7.2 Hz),
4.06–4.10 (m, 1H, H-b’), 3.87 (q, 1H, H-6, J = 7.6 Hz),
3.42–3.50 (m, 2H, H-a’), 2.39 (d, 2H, H-3, J = 7.6 Hz),
2.26 (t, 2H, H-9, J = 7.2 Hz), 1.90–1.98 (m, 1H, H-2), 1.68
(d, 3H, H-7, J = 7.6 Hz), 0.94 (d, 6H, H-1, J = 7.6 Hz).
2.3 | Synthesis of the complex 1, (LE)au
(LC)
To [Au (LC)Cl] (328 mg, 1 mmol) in dichloromethane
(7 ml) was added Na2CO3 (318 mg, 3 mmol) and ligand
LE (258 mg, 1 mmol). The reaction stirred at room tem-
perature for 52 hr. Then, 30 ml of deionized water was
added and stirred for 3 hr. The organic layer was
extracted into dichloromethane and dried over MgSO4
and concentrated in rotavap. The pure complex was
obtained by recrystallization from dichloromethane/hex-
ane (1:8). Yellow solids (294.13 mg, 53.46% yield, and
+
1
1
mmol). Anal. Calc. (%) for C22H29AuN2O2
(550.1895): C, 48.00; H, 5.31; N, 5.09; Found (%): C,
+
1
47.97; H, 5.29; N, 5.07. TOF-MS: 551.1973 [M + H] . H
NMR (DMSO-d6): δ 7.43 (s, 2H, H-a), 7.26 (d, 2H, H-5,
J = 7.6 Hz), 7.09 (d, 2H, H-4, J = 7.6 Hz), 4.30 (t, 2H, H-
8, J = 7.2 Hz), 3.92 (q, 1H, H-6, J = 7.6 Hz), 3.70 (s, 6H,
H-b), 2.34 (d, 2H, H-3, J = 7.6 Hz), 2.19 (t, 2H, H-9,
J = 7.2 Hz), 1.89–1.94 (m, 1H, H-2), 1.65 (d, 3H, H-7,
J = 7.6 Hz), 0.95 (d, 6H, H-1, J = 7.6 Hz). 13C NMR
(DMSO-d6): δ 175.1 (C=O), 169.9 (Cc), 144.1 (Ar), 135.8
(Ar), 133.6 (Ar), 131.9 (Ar), 123.4 (Ca), 85.0 (C10), 75.1
(C11), 61.2 (C8), 45.0 (C3), 37.0 (C6), 36.1 (Cb), 29.9 (C2),
24.1 (C9), 19.4 (C1), 11.9 (C7).
2.6 | Stability tests
The stability of the ligand LE, complexes 1 and 2 was
tested by dissolving the compound in PBS buffer/1%
ꢀ
DMSO and keeping them for 3 days at 37 C. Briefly, a
15 μL of the solution was injected into an HPLC system
(Thermo, Milford, MA, USA) connected to a UV/Vis
spectrophotometer with 260 nm UV detection at room
temperature. The mobile phase was 80:20 acetonitrile
(0.1%.
2.4 | Synthesis of the complex 2, (LE)au
(PPh3)
trifluoroacetic acid): water (0.1% trifluoroacetic acid).
A Hypersil Gold Dim (100 × 2.1 mm, Thermo, Milford,
MA, USA) reversed-phase column was used at a flow rate
The synthesis was carried out as described for 1, with
Au (PPh3)Cl (494 mg, 1 mmol) instead of [Au (LC)Cl].
Yellow solids (519 mg, 72.51% yield, and 1 mmol). Anal.
Calc. (%) for C35H36AuO2P (716.2118): C, 58.66; H,
of 0.5 ml min −1
.
2.7 | Cell culture
5.06; P, 4.32; Found (%): C, 58.64; H, 5.05; P, 4.29. TOF-
+
MS: 717.2197 [M + H]
.
1H NMR (DMSO-d6): δ
The human MCF-7 and MDA-MB-231 breast cancer cell
lines and HT-29 colon cancer were obtained from the
American Type Culture Collection (ATCC, Manassas,
VA, USA). All reagents and cell culture media were pur-
chased from Gibco Company (Germany). The cells were
maintained in Dulbecco's Modified Eagle Medium
(DMEM) supplemented with 10% FBS, 100 IU ml−1 of
penicillin, 100 μg ml−1 of streptomycin and 2 mM of Glu-
tamax at 37 ꢀC in a humidified incubator at 5% CO2. The
adherent cultures were grown as monolayers and were
passaged once in 4–5 days by trypsinizing them with
0.25% Trypsin–EDTA. MCF-10A, a non-tumor breast cell
7.51–7.65 (m, 15H, H-Ar (PPh3)), 7.29 (d, 2H, H-5,
J = 7.6 Hz), 7.08 (d, 2H, H-4, J = 7.6 Hz), 4.27 (t, 2H,
H-8, J = 7.2 Hz), 3.90 (q, 1H, H-6, J = 7.6 Hz), 2.37 (d,
2H, H-3, J = 7.6 Hz), 2.17 (t, 2H, H-9, J = 7.2 Hz),
1.87–1.91 (m, 1H, H-2), 1.69 (d, 3H, H-7, J = 7.6 Hz),
0.92 (d, 6H, H-1, J = 7.6 Hz). 13C NMR (DMSO-d6): δ
173.3 (C=O), 142.2 (Ar), 136.2 (Ar), 134.1 (Ar), 133.2
(Ar), 131.7 (Ar), 130.0 (Ar), 129.0 (Ar), 127.3 (Ar), 87.3
(C10), 77.4 (C11), 60.4 (C8), 45.7 (C3), 36.3 (C6), 29.9
(C2), 24.0 (C9), 20.0 (C1), 12.2 (C7). 31P NMR (DMSO-
d6): δ 32.12 (s, PPh3).

4 of 10
TABRIZI AND ROMANOVA
line, obtained from ATCC, Manassas, VA, USA, was cul-
tivated in DMEM/F12 medium containing horse serum
(HS) 5%, EGF (0.02 mg/ml); hydrocortisone (0.05 mg/ml);
cholera toxin (0.001 mg/ml), insulin (0.01 mg/ml), peni-
cillin (100 UI/ml), streptomycin (100 mg/ml) and L-
glutamine (2 mM).
to each dish that freshly prepared complex 1 or 2 was
added to cells at IC50 concentrations. The dishes were
incubated at 37 ꢀC under for a period of 24 hr. The
growth medium was removed and each dish was washed
with PBS. Trypsin (0.25% in PBS) was added, and cells
were
harvested
from
the
plate
by
using
ethylenediaminetetraacetic acid (EDTA)-trypsin and cen-
trifuged. Dishes were washed with PBS, and this was
added to the cell suspension to ensure that all the cells
were collected. The resulting suspension was centrifuged,
and the supernatant was discarded. The cell pellet was
washed with PBS (2 ml) and saline (0.9% NaCl, 99.999%
pure, 2 ml), and the supernatant was discarded each
time. The number of cells per dish was determined by
scoring one dish out of each series of four. The Au con-
tent was determined by graphite furnace atomic absorp-
tion spectroscopy, after digestion of the cells in
concentrated HNO3 (Tracepur, Merck) and dilution to
10.0 ml. All the measurements were done in triplicate.
2.8 | Cytotoxicity
The MCF-7, MDA-MB-231, HT-29, and MCF-10A were
analyzed for viability post treatment using the MTT
(3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bro-
mide) assay following previously reported procedures.[45]
The stock solutions of auranofin, free ligands, and com-
plexes 1 and 2 were prepared by dissolving the compounds
in DMSO (0.1%) and for cisplatin by dissolving in 0.9%
NaCl. The stocks were further diluted with the respective
medium containing 10% FBS (0.02–10 μM) before addition
to the cells. Cells were trypsinized with 0.25% trypsin–
EDTA and counted with 0.4% trypan blue. The cells were
seeded at a concentration of (3–8) × 103 cells/well, depen-
dent upon the growth characteristics of the cell line, and
2.10 | Preparation of thioredoxin
reductases
ꢀ
grown for 24 h at 37 C in a humidified incubator. After
24 hr, the medium was removed and replaced with fresh
medium containing the compound to be studied at the
appropriate concentration. Triplicate cultures were
established for each treatment. After 72 hr, each well was
treated with 10 μl of a 5 mg/ml MTT saline solution, and,
following 5 hr of incubation, 100 μl of a sodium dode-
cylsulfate solution in HCl (0.01 M) was added. The optical
absorbance of each well (96-well plates) was quantified
using EnVision multilabel plate readers (PerkinElmer,
Waltham, MA, USA) at 570 nm wavelength. The mean
absorbance for each drug dose was expressed as a percent-
age of the control, untreated well absorbance and plotted
vs drug concentration. The IC50 values were determined
by nonlinear regression analysis using GraphPad Prism
software. The IC50 value was calculated as the concentra-
tion reducing the proliferation of the cells by 50% and is
presented as a mean ( SE) of three independent experi-
ments each with triplicates. P < 0.05 was considered to be
statistically significant. SI (selectivity index) was obtained
average IC50 for MCF-10A normal cells divided by average
IC50 for MCF-7, MDA-MB-231, and HT-29 cancer cells.
The cytosolic thioredoxin reductase (TrxR1), mitochon-
drial thioredoxin reductase (TrxR2) from rat liver, and
glutathione reductase (GR) were obtained from Sigma-
Aldrich and used without further purification.
2.11 | In vitro TrxR1 and TrxR2
inhibition
The assay was performed in 0.2 M Na, K-phosphate
buffer (pH 7.2) containing 2 mM EDTA, 0.25 mM
NADPH (Nicotinamide adenine dinucleotide phosphate)
and about 0.5–2 μg of TrxR protein. The reaction was ini-
tiated by the addition of 3 mM DTNB (5,50-dithiobis
(2-nitrobenzoic acid)) to both sample and reference and
the increase of absorbance was monitored at 412 nm over
ꢀ
5 min at 25 C. Enzyme activity was calculated taking
into account that 1 mole of NADPH yields 2 moles of
CNTP anion (reduced DTNB). All the measurements
were done in triplicate.
2.9 | Cellular uptake
2.12 | In vitro GR inhibition
HT-29 cancer cells were seeded at a density of 106
cells/dish and maintained at 37 C in a 5% CO2 atmo-
sphere. Cells were washed with phosphate-buffered
saline (PBS), and fresh growth medium (5 ml) was added
Glutathione reductase activity was assessed at 25 ꢀC
in 0.1 M Tris–HCl (pH 8.0) containing 0.2 mM
NADPH. Reactions were started by the addition of 1 mM
ꢀ
GSSG
(oxidized
glutathione)
and
followed

GOLD(I) N-HETEROCYCLIC CARBENE AND TRIPHENYLPHOSPHINE COMPLEXES
5 of 10
spectrophotometrically at 340 nm. All the measurements
were done in triplicate.
The choice of the computational procedure is based
on the recent paper of Dos Santos et al.[56] The authors
demonstrated that the B3LYP/LanL2TZ&6–31 + G(2df)
and wB97XD/LanL2TZ&6–31 + G(2df) approaches are
appropriate to model the thermochemistry of the ligand
exchange reaction between LC-Au-LC complex and
HCys. However, for the PPh3-Au-LE complex conver-
gence problems occurred with the 6–31 + G(2df) bas-
is set due to the bulkiness of the PPh3 ligand in
combination with diffuse functions. Therefore, in the
case of the PPh3-Au-LE complex only results with Lan-
L2TZ(f)&6-31G(d) basis set are reported.
2.13 | Reactive oxygen species (ROS)
assay
The induction of intracellular oxidative stress in HT-29
cells was measured using a 20,70-dichlorofluorescein dia-
cetate (DCFH-DA) dye which produces fluorescence on
the production of reactive oxygen species. Briefly, cells
were seeded into IBIDI 96-well plates at a density of
3
ꢀ
3 × 10 cells/well and were incubated for 24 hr at 37 C.
The medium was removed and 100 μL of a 20 μM DCFH-
DA solution in PBS was added to each well and incu-
ꢀ
bated at 37 C and 5% CO2 for 25 min in darkness. Cells
3 | RESULTS AND DISCUSSION
3.1 | Synthesis and characterization
were washed twice with 100 μL PBS and then treated
with PBS alone (untreated control), antimycin (3 μM,
Sigma Chemical Co., a potent inhibitor of Complex III in
the electron transport chain, as positive control), and
IC50 concentration of each of the complexes 1 and 2 and
fluorescence was measured after 90 min. Reactive oxygen
species levels were determined by measuring the fluores-
cence of oxidized DCFH-DA using a spectramax M3 mul-
tiplate reader with excitation at 485 nm and emission at
530 nm. The ROS levels were normalized to control in
each time using GraphPad Prism software. The final
Au (PPh3)Cl (PPh3: triphenylphosphine)[43] and [Au (LC)
Cl] (LC: 1,3-dimethylimidazol-2-ylidene)[44] were synthe-
sized as described previously. The ligand 3-yn-1-yl
2-(4-isobutylphenyl)propanoate (LE) was synthesized by
coupling the ibuprofen and 3-Butyn-1-ol as described in
experimental part and Scheme S1. The complex (LE)Au
(LC), 1 and complex (LE)Au (PPh3), 2 were prepared by
reacting the ligand LE with [Au (LC)Cl] and Au (PPh3)Cl
in the presence of Na2CO3, respectively (Scheme S2 and
Scheme S3).
value is the mean
S.D. of at least three independent
experiments performed in triplicate. P < 0.05 was consid-
ered to be statistically significant.
The ligand LE, complexes 1 and 2 were characterized
by multinuclear NMR (1H, 13C, and 31P), and mass spec-
trometry and their high purity was confirmed by elemen-
tal analysis (see Figures S1-S3, S5-S11 of the Supporting
1
2.14 | Computational protocol
Information). The obtained signals of H and 13C NMR
spectra were consistent with the proposed structures of
the ligand LE, complexes 1 and 2. Formation of com-
plexes 1 and 2 were noticeably approved by the absence
of the terminal hydrogen signal of the ligand LE
All reactants and products (Figure 3) were subject to
geometry optimization and frequency analysis: LC,
[LE]−, HCys, PPh3, LC-Au-LE, PPh3-Au-LE, HCys-Au-
LE, [Cys-Au-LE]−, HCys-Au-Cys and [Cys-Au-Cys]−. The
calculations were performed with the B3LYP[46] and
wB97XD[47] functionals. The LanL2TZ(f) basis set and
pseudopotentials were applied for Au.[48–50] The rest of
the atoms were described by using 6–31 + G(2df) or
6-31G(d) basis sets. The electrostatic interaction with the
solvent (water, ε0 = 78.35) was taken into account
by using polarizable continuum model (PCM) in its inte-
gral equation formalism variant.[51–53] The frequency
analysis shows that all optimized structures represent
true minima on the potential energy surface. The calcula-
tions were realized with the Gaussian 09 program
package.[54] The molecular orbitals were visualized using
the GaussView 5[55] graphical interface and isosurface
value of 0.02.
1
(as singlet at 2.89 ppm) in H NMR spectra. The ESI-MS
spectra of ligand LE, complexes 1 and 2 showed
[M + H]+ peaks centered at m/z = 259.16, 551.19, and
717.21, respectively.
In order to reveal the cytotoxicity mechanism toward
DNA, the interaction of complexes 1 and 2 with cysteine
we already introduced it carried out by with 5 equiv of
cysteine in DMF (Scheme S4). The final product, (LE)Au
(HCys), 3 was observed in both complexes 1 and 2 by
replacing ligand LC (in complex 1) and PPh3 (in complex
2) through cysteine. This observation was approved by
theoretical study. The complex 3 was also confirmed by
1H NMR, ESI-MS spectrometry and elemental analyses
1
(Figure S4 and S12). H spectrum of complex 3 revealed
Ha’ and Hb’ cysteine as multiplate at 3.42–3.50 ppm and

6 of 10
TABRIZI AND ROMANOVA
TABLE 1 In vitro antitumor activitya
IC50 (μM) S.D.
Compounds
PPh3
HT-29
MDA-MB-231
>100
MCF-7
MCF-10A
SI
-
>100
>100
-
-
-
LE
>100
>100
>100
-
LC
>100
>100
>100
-
Complex 1
Complex 2
Cisplatin
Auranofin
2.32 0.10
0.98 0.05
4.17 0.25
2.94 0.12
3.18 0.05
1.97 0.10
7.41 0.12
5.14 0.13
3.42 0.15
1.25 0.05
2.17 0.40
1.82 0.12
67.65 0.52
89.25 0.42
35.42 0.32
47.25 0.60
22.78
63.75
7.73
14.32
aThe compounds was dissolved in 0.1% of DMSO and diluted with water and cisplatin was dissolved in 0.9% NaCl solution. Cells were treated for 72 hr with
increasing concentrations of tested compounds. IC50 values were calculated by four parameter logistic model (p < 0.05). S.D. = standard deviation.
4.06–4.10 ppm, respectively. In the ESI-MS spectrum, the
active than auranofin against HT-29, MDA-MB-231,
MCF-7 cancer cell lines.
+
576.14 [M + H]
parent ion of the complex 3 was
observed.
In order to determine the correlation between cyto-
toxicity of the compounds with intracellular gold accu-
mulation, the uptakes of complexes 1 and 2 (at IC50
concentrations) were studied in HT-29 cancer cells by the
graphite furnace atomic absorption spectroscopy (GF-
AAS). In the HT-29 cells, the amounts of gold were
detected as 47.3
121.3
1.2 ng Au/106 cells (2) after 24 hr treatment.
These results showed the correlation of cellular uptake
with the growth inhibitory potency by complexes 1 and
2 in HT-29 cancer cells.
The complexes 1 and 2 were also tested against non-
tumor breast cell line, MCF-10A. Both complexes 1 and
2 were less active in the healthy cell than cisplatin and
auranofin. The calculated SI (selectivity index) value was
63.75 for complex 2 and approximately 8.24 and 4.45
times higher than that obtained for cisplatin and
auranofin, respectively.
3.2 | Solution stability study
To endorse the stability of ligand LE, and complexes
1 and 2 in biological environment, the stability test was
performed in a solution phase (DMSO/PBS, 1:99 v/v) by
0.6 ng Au/106 cells (1) and
ꢀ
HPLC-UV at 37 C during 72 hr (Figure S13). There was
no detectable change in retention time during 3 days,
confirming the stability of these compounds under physi-
ological conditions.
3.3 | Cytotoxicity studies and cellular
uptake
In vitro cytotoxic activities of the free ligands, complexes
1 and 2 have been performed against MCF-7, MDAMB
231 breast cancer cells, and HT-29 colon cancer cells as
well as non-tumor breast cell line (MCF-10A) and com-
pared with cisplatin and auranofin as reference drugs
(Table 1). Cytotoxicity was evaluated via MTT assay after
72 hr treatment. The ligands PPh3, LE, and LC were inac-
tive against MCF-7, MDA-MB 231, and HT-29 cells
(IC50 > 100 μM). The complex 1 exhibits higher activity
against the HT-29 cell line (IC50 = 2.32 0.10 μM) than
against MDA-MB-231 (IC50 = 3.18 0.05 μM). However,
complex 1 is less active than cisplatin and auranofin in
MCF-7 cells. It is approximately 1.8 and 2.3 times more
active than cisplatin against HT-29 and MDA-MB-231
3.4 | Enzyme inhibition studies
Thioredoxin reductases (TrxR) are the only known
enzymes to reduce thioredoxin (Trx) and also the main
target for the gold complexes. Therefore, the gold
TABLE 2 Inhibitory effect of compounds on TrxR1, TrxR2,
and GR a
IC50 (μM)
Compounds
TrxR1
TrxR2
GR
cells, respectively. Moreover, complex
2
showed
1
0.007 0.001
0.004 0.001
0.009 0.001
0.062 0.01
0.041 0.01
0.006 0.001
> 15
> 15
> 15
improved cytotoxic activity in comparison to complex 1.
Complex 2 is 4.2, 3.7, and 1.7 fold more active than cis-
platin against HT-29, MDA-MB-231, MCF-7 cancer cell
lines, respectively. In addition, complex 2 was more
2
Auranofin
aThe reported values are the mean SD of at least three exper.

GOLD(I) N-HETEROCYCLIC CARBENE AND TRIPHENYLPHOSPHINE COMPLEXES
7 of 10
However, both complexes 1 and 2 are approximately
10 times less active against mitochondrial thioredoxin
reductase (TrxR2) than auranofin with the order of activ-
ity as auranofin >2 > 1. Moreover, both complexes 1 and
2 showed a significant ability of inhibiting GR at high
concentration (> 15 μM), signifying a superior binding
mode of complexes 1 and 2 for purified TrxR.
3.5 | Reactive oxygen species (ROS)
generation
TrxR enzyme inhibition enhances the hydrogen peroxide
and reactive oxygen species levels. This causes an imbal-
ance in cell redox environments in mitochondrial mem-
brane permeabilization (MMP) and cell apoptosis.[57,58]
Therefore, the ROS levels measurements in HT-29 cells
by treatment with complexes 1 and 2 (IC50 concentration)
were performed. Both complexes 1 and 2 increase the
ROS levels to 5.1 and 8.3 folds as compared with the con-
trol (Figure 2). Moreover, complexes 1 and 2 showed
higher ROS levels in comparison with antimycin as posi-
tive control. Complex 2 showed higher ROS level than
complex 1. This result is in good agreement with the
results from the cytotoxicity assay and the high influence
in TrxR inhibition in comparison with complex 1. Over-
all, the anticancer activity of the complexes 1 and 2 can
be regarded as a result of TrxR based ROS generation.
FIGURE 2 Fluorescent detection of ROS using DCFDA in
HT-29 cells with exposure to complexes 1 and 2 after 90 min.
Antimycin was used as a positive control
complexes 1 and 2 was considered against purified cyto-
solic (TrxR1) and mitochondrial (TrxR2) thioredoxin
reductase and compared with auranofin as reference
drug. Also, the inhibition of glutathione reductase
(GR) with the structure (but non-selenocysteine residue)
closely related to that of TrxR, was explored to conclude
the selectivity of enzyme inhibition (Table 2). The activity
of cytosolic TrxR (TrxR1) is remarkably inhibited by both
complexes 1 and 2, exposing IC50 values in the
nanomolar range, comparable to the case for auranofin,
following the order of activity 2 > 1 > auranofin.
3.6 | Computational studies
The cytotoxicity of complexes 1 and 2 was explained by
assuming two-step ligand exchange reaction with HCys
(Figure 3).[19,52] Our DFT calculations indicate that the
first and second steps of these ligand exchange reactions
for the newly synthetized complexes are endergonic
(Table 3). The latter is consistent with previously
reported theoretical and experimental results for NHC
gold complexes.[52] For complexes 1 and 2 the first
FIGURE 3 Two-step ligand exchange reaction between LC-Au-LE complex and cysteine: LC = 1,3-dimethylimidazol-2-ylidene,
LE = ibuprofen-alkynyl; HCys = cysteine, Cys = deprotonated cysteine. The same reaction path is considered for the PPh3-Au-LE complex,
where PPh3 = P(C6H5)3

8 of 10
TABRIZI AND ROMANOVA
TABLE 3 PCM/DFT results for the free energy ΔGa [kcal/mol] of the ligand exchange reactions
LC
PPh3
[LE]−
1st reaction step
32.57
1st reaction step
2nd reaction step
B3LYP/LanL2TZ(f)&6–31 + G(2df)
B3LYP/LanL2TZ(f)&6-31G(d)
na
41.67
64.56
40.34
63.54
38.50
8.58
na
wB97XD/LanL2TZ(f)&6–31 + G(2df)
wB97XD/LanL2TZ(f)&6-31G(d)
32.20
39.18
16.75
na = not available.
reaction step is less endergonic than the second one. In
addition, the first reaction step is less endergonic in the
case of PPh3-Au-LE (~9 kcal/mol) than in the case of the
LC-Au-LE complex (~39 kcal/mol). The free energy
results are qualitatively independent on the choice of the
DFT functional and basis sets. For both ligand exchange
reactions, stable products are predicted by quantum-
chemical calculations, which is consistent with the exper-
imental observations. Information on the optimized
structure of the complexes (metal–ligand bond lengths)
can be found in SI, Table S1.
Dos Santos et al. reported linear dependence between
the activation enthalpy of the ligand exchange reaction
and the energy of the σ-orbital for the isolated ligand (Eσ-
HOMO).[52] The latter is also a measure for the σ-donor
strength of the ligand. The activation enthalpy increases
when the energy of the σ-orbital of the isolated ligand
grows. In other words, ligands that are stronger σ-donors
require higher activation energy to be replaced by HCys.
Our DFT results show that the Eσ-HOMO increases as
PPh3(−5.97 eV) < LC(−5.81 eV) < [LE]− (−5.01 eV)
(Table 4). Therefore, it is expected that the activation
enthalpy for the PPh3-Au-LE + HCys ! HCys-Au-
LE + PPh3 reaction is lowest, followed by the case of the
LC-Au-LE + HCys ! HCys-Au-LE + LC ligand
exchange reaction. Highest activation enthalpy is
expected if the first leaving ligand is [LE]−: LC-Au-
LE + HCys ! LC-Au-HCys + [LE]− or PPh3-Au-
LE + HCys ! PPh3-Au-HCys + [LE]−. These results are
in agreement with the proposed mechanism (Figure 4)
where the [LE]− ligand is replaced in the second reaction
step. Moreover, our results suggest that the energy of the
σ-orbital for the isolated ligand (Table 4) and the activa-
tion enthalpy for the first reaction step can be related to
the cytotoxicity of the complexes. The contour plots for
the key orbitals of the isolated ligands are represented in
Figure 4. The experimentally measured cytotoxicity
(Table 1) is higher for the PPh3-Au-LE complex than for
the LC-Au-LE compound. Therefore, it can be speculated
that the cytotoxicity of the complex increases when the σ-
donor ability and the activation enthalpy for the first
reaction step decreases. From molecular design perspec-
tive, this can serve as a guideline for creation of new
gold-based anticancer drugs; however, larger dataset of
compounds is needed in order to estimate the predictive
power of the revealed relationship.
TABLE 4 PCM/B3LYP/6-31G(d) results for the energy of the
σ-type orbitals [eV] of the isolated ligands
LC
[LE]−
−4.82π
−5.01
PPh3
EHOMO
−5.81
−5.97
EHOMO-2
πIn the case of the [LE]− ligand HOMO is of π-type.
FIGURE 4 Contour plots for the key orbitals calculated for the isolated ligands with PCM/B3LYP/6-31G(d)

GOLD(I) N-HETEROCYCLIC CARBENE AND TRIPHENYLPHOSPHINE COMPLEXES
9 of 10
[2] L. Kelland, Nat. Rev. Cancer 2007, 7, 573.
[3] C. F. Shaw, Chem. Rev. 1999, 99, 2589.
[4] I. Ott, Coord. Chem. Rev. 2009, 253, 1670.
[5] R. Rubbiani, L. Salassa, A. de Almeida, A. Casini, I. Ott,
ChemMedChem 2014, 9, 1205.
4 | CONCLUSIONS
A series of gold(I) complexes of ligand ibuprofen-alkynyl
(but-3-yn-1-yl 2-(4-isobutylphenyl)propanoate, LE) with
N-heterocyclic carbene (LC: 1,3-dimethylimidazol-
2-ylidene) and triphenylphosphine (PPh3) ligands with
formula (LE)Au (LC) (complex 1) and (LE)Au (PPh3)
(complex 2) were synthesized and fully characterized.
Interaction of complex 1 or 2 with cysteine (HCys) was
studied by experimental and theoretical methods, which
showed that ligand LC or PPh3 was replaced by cysteine.
The compounds were investigated for their anticancer
activity against MCF-7, MDAMB 231 breast cancer cells,
and HT-29 colon cancer cells and compared with cis-
platin as reference drug. The complex 2 showed more
cytotoxic activity than complex 1. The complex 2 was 4.2,
3.7, and 1.7 fold more active than cisplatin against HT-
29, MDA-MB-231, MCF-7 cancer cell line, respectively.
The activity of cytosolic TrxR (TrxR1) is inhibited by the
complexes 1 and 2 with IC50 values in the nanomolar
range and more active than auranofin. Also, the com-
plexes 1 and 2 were 10 times more active than auranofin
about against mitochondrial thioredoxin reductase
(TrxR2). For both TrxR1 and TrxR2, complex 2 was more
active than complex 1. However, 1 and 2 were less active
against glutathione reductase (GR) than auranofin that
confirmed the inhibiting ability of complexes 1 and 2 for
purified TrxR. Both complexes 1 and 2 increase the ROS
levels to 5.1 and 8.3 folds as compared with the control
and more than antimycin as positive control. Therefore,
the mechanism of anticancer activity of the complexes
1 and 2 can be as strong inhibition of thioredoxin reduc-
tase with the increased ROS generation. From molecular
design perspective, a relationship between the σ-donor
ability of the isolated ligands and the cytotoxicity of the
gold complex is suggested.
[6] T. S. Reddy, S. H. Privér, V. V. Rao, N. Mirzadeh,
S. K. Bhargava, Dalton Trans. 2018, 47, 15312.
[7] T. Marzo, D. Cirri, C. Gabbiani, T. Gamberi, F. Magherini,
A. Pratesi, A. Guerri, T. Biver, F. Binacchi, M. Stefanini,
A. Arcangeli, L. Messori, ACS Med. Chem. Lett. 2017, 8, 997.
[8] A. De Nisi, C. Bergamini, M. Leonzio, G. Sartor, R. Fato,
M. Naldi, M. Monari, N. Calonghi, M. Bandini, Dalton Trans.
2016, 45, 1546.
[9] T. Zou, C. T. Lum, C. N. Lok, J. J. Zhang, C. M. Che, Chem.
Soc. Rev. 2015, 44, 8765.
[10] B. Bertrand, A. Casini, Dalton Trans. 2014, 43, 4209.
[11] M. J. McKeage, L. Maharaj, S. J. Berners-Price, Coord. Chem.
Rev. 2002, 232, 127.
[12] M. A. Bennett, S. K. Bhargava, K. D. Griffiths,
G. B. Robertson, W. A. Wickramsinghe, A. C. Willis, Angew.
Chem. Int. Ed. Engl. 1987, 26, 258.
[13] M. Porchia, M. Pellei, M. Marinelli, F. Tisato, F. Del Bello,
C. Santini, Eur. J. Med. Chem. 2018, 146, 709.
[14] W. Liu, K. Bensdorf, M. Proetto, U. Abram, A. Hagenbach,
R. Gust, J. Med. Chem. 2011, 54, 8605.
[15] Ö. Karaca, V. Scalcon, S. M. Meier-Menches, R. Bonsignore,
J. M. J. L. Brouwer, F. Tonolo, A. Folda, M. P. Rigobello,
F. E. Kühn, A. Casini, Inorg. Chem. 2017, 56, 14237.
[16] W. Liu, R. Gust, Coord. Chem. Rev. 2016, 329, 191.
[17] L. Oehninger, R. Rubbiani, I. Ott, Dalton Trans. 2013, 42,
3269.
[18] J. L. Hickey, R. A. Ruhayel, P. J. Barnard, M. V. Baker,
S. J. Berners-Price, A. Filipovska, J. Am. Chem. Soc. 2008, 130,
12570.
[19] A. Bindoli, M. P. Rigobello, G. Scutari, C. Gabbiani, A. Casini,
L. Messori, Coord. Chem. Rev. 2009, 253, 1692.
[20] S. Urig, K. Fritz-Wolf, R. Reau, C. Herold-Mende, K. Toth,
E. Davioud-Charvet, K. Becker, Angew. Chem. 2006, 118, 1915.
Angew. Chem. Int. Ed. 2006, 45, 1881.
[21] A. Pratesi, C. Gabbiani, E. Michelucci, M. Ginanneschi,
A. M. Papini, R. Rubbiani, I. Ott, L. Messori, J. Inorg. Biochem.
2014, 136, 161.
ACKNOWLEDGEMENTS
[22] M. Mora, M. C. Gimeno, R. Visbal, Chem. Soc. Rev. 2019,
48, 447.
The authors would like to thank the School of Chemistry,
National University of Ireland (NUI), Galway for general
support and the Laboratory of Quantum and Computa-
tional Chemistry at the Sofia University for the provided
computing resources.
[23] M. Fereidoonnezhad, H. R. Shahsavari, E. Lotfi,
M. Babaghasabha, M. Fakhri, Z. Faghih, Z. Faghih,
M. H. Beyzavi, Appl. Organomet. Chem. 2018, 32, e4200.
[24] O. Dada, D. Curran, C. O'Beirne, H. Müller-Bunz, X. Zhu,
M. Tacke, J. Organomet. Chem. 2017, 840, 30.
[25] M.
S.
Fereidoonnezhad,
Abedanzadeh, A.
H.
Yazdani,
Ahmadi
A.
Mirsadeghi,
Alamdarlou,
NOTES
All authors declare no conflict of interest.
M. Babaghasabha, Z. Almansaf, Z. Faghih, Z. McConnell,
H. R. Shahsavari, M. H. Beyzavi, New J. Chem. 2019, 43,
13173.
ORCID
Leila Tabrizi https://orcid.org/0000-0002-3699-5869
ꢀ
ꢀ
[26] M. D. Đurovic, Ž. D. Bugarcˇic, R. van Eldik, Coord. Chem. Rev.
2017, 338, 186.
REFERENCES
[27] S. Kumar, S. Garg, R. P. Sharma, P. Venugopalan, L. Tenti,
L. Ferretti, L. Nivelle, M. Tarpic, E. Guillon, New J. Chem.
2017, 41, 8253.
[1] B. Rosenberg, L. Van Camp, J. E. Trosko, V. H. Mansour,
Nature 1969, 222, 385.

10 of 10
TABRIZI AND ROMANOVA
[28] D. M. Schreinemachers, R. B. Everson, Epidemiology 1994,
5, 138.
[52] R. Cammi, B. Mennucci, J. Chem. Phys. 1999, 110, 9877.
[53] J. Tomasi, B. Mennucci, R. Cammi, Chem. Rev. 2005, 105,
2999.
ꢀ
[29] M. W. Szkudlinski, Med. Hypotheses 1992, 39, 265.
[30] S. Hashitani, M. Urade, N. Nishimura, T. Maeda, K. Takaoka,
K. Noguchi, K. Sakurai, Int. J. Oncol. 2003, 23, 665.
[31] S. Srinivas, D. A. Feldman, Anticancer Res. 2009, 29, 3605.
[32] F. Khwaja, J. Allen, J. Lynch, P. Andrews, D. Djakiew, Cancer
Res. 2004, 64, 6207.
[33] K. D. Rainsford, Ibuprofen: pharmacology, therapeutics and
side effects, Springer Science & Business Media, Springer Basel
2013.
[54] M. J. Frisch, G. W. Trucks, H. B. Schlegel, G. E. Scuseria,
M. A. Robb, J. R. Cheeseman, G. Scalmani, V. Barone,
B. Mennucci, G. A. Petersson, H. Nakatsuji, M. Caricato, X. Li,
H. P. Hratchian, A. F. Izmaylov, J. Bloino, G. Zheng,
J. L. Sonnenberg, M. Hada, M. Ehara, K. Toyota, R. Fukuda,
J. Hasegawa, M. Ishida, T. Nakajima, Y. Honda, O. Kitao,
H. Nakai, T. Vreven, J. A. Montgomery Jr., J. E. Peralta,
F. Ogliaro, M. Bearpark, J. J. Heyd, E. Brothers, K. N. Kudin,
V. N. Staroverov, R. Kobayashi, J. Normand, K. Raghavachari,
A. Rendell, J. C. Burant, S. S. Iyengar, J. Tomasi, M. Cossi,
N. Rega, J. M. Millam, M. Klene, J. E. Knox, J. B. Cross,
V. Bakken, C. Adamo, J. Jaramillo, R. Gomperts,
R. E. Stratmann, O. Yazyev, A. J. Austin, R. Cammi,
C. Pomelli, J. W. Ochterski, R. L. Martin, K. Morokuma,
V. G. Zakrzewski, G. A. Voth, P. Salvador, J. J. Dannenberg,
S. Dapprich, A. D. Daniels, Ö. Farkas, J. B. Foresman,
J. V. Ortiz, J. Cioslowski, D. J. Fox, Gaussian 09, Revision
D.01, Gaussian, Inc., Wallingford CT, 2009.
[34] C. M. Manzano, F. R. G. Bergamini, W. R. Lustri, A. L.
T.
G.
Ruiz,
E.
C.
S.
de
Oliveira,
M. A. Ribeiro, A. L. B. Formiga, P. P. Corbi, J. Mol. Struct.
2018, 1154, 469.
[35] H. Chiniforoshan, L. Tabrizi, M. Hadizade, M. R. Sabzalian,
A. N. Chermahini, M. Rezapour, Acta a Mol. Biomol. Spectrosc.
2014, 128, 183.
[36] I. M. e Silva, D. de Moraes Profirio, R. E. de Paiva,
M. Lancellotti, A. L. Formiga, P. P. Corbi, J. Mol. Struct. 2013,
1049, 1.
~
[37] A. T. M. Fiori, W. R. Lustri, A. Magalhaes, P. P. Corbi, Inorg.
[55] R. Dennington, T. Keith, J. Millam, GaussView, Version
5, Semichem Inc., Shawnee Mission, KS, 2009.
Chem. Commun. 2011, 14, 738.
[38] C. Dendrinou-Samara, G. Tsotsou, L. V. Ekateriniadou,
A. H. Kortsaris, C. P. Raptopoulou, A. Terzis, D. A. Kyriakidis,
D. P. Kessissoglou, J. Inorg. Biochem. 1998, 71, 171.
[56] H. F. Dos Santos, M. A. Vieira, G. Y. Sánchez Delgado,
D. Paschoal, J. Phys. Chem. A 2016, 120, 2250.
[57] R. Rubbiani, S. Can, I. Kitanovic, H. Alborzinia,
M. Stefanopoulou, M. Kokoschka, S. Monchgesang,
W. S. Sheldrick, S. Wölfl, I. Ott, J. Med. Chem. 2011, 54, 8646.
[58] T. Srinivasa Reddy, S. H. Privér, V. V. Rao, N. Mirzadeh,
S. K. Bhargava, Dalton Trans. 2018, 47, 15312.
[39] P. Mandal, B. K. Kundu, K. Vyas, V. Sabu,
A.
Helen,
S.
S.
Dhankhar,
C.
M.
Nagaraja,
D. Bhattacherjee, K. P. Bhabake, S. Mukhopadhyay, Dalton
Trans. 2018, 47, 517.
[40] W. Neumann, B. C. Crews, L. J. Marnett, E. Hey-Hawkins,
ChemMedChem 2014, 9, 1150.
[41] L. Tabrizi, D. Q. Dao, T. A. Vu, RSC Adv. 2019, 9, 3320.
[42] L. Tabrizi, L. O. Olasunkanmi, O. A. Fadare, Dalton Trans.
2019, 48, 728.
[43] M. I. Bruce, B. K. Nicholson, O. B. Shawkataly, Inorg. Synth.
1989, 26, 324. https://doi.org/10.1002/9780470132579.ch59
[44] H. M. J. Wang, C. Y. L. Chen, I. J. B. Lin, Organometallics
1999, 18, 1216.
[45] T. Mosmann, J. Immunol. Methods 1983, 65, 55.
[46] A. D. Becke, J. Chem. Phys. 1993, 98, 5648.
[47] J.-D. Chai, Phys. Chem. Chem. Phys. 2008, 10, 6615.
[48] P. J. Hay, W. R. Wadt, J. Chem. Phys. 1985, 82, 270.
[49] W. R. Wadt, P. J. Hay, J. Chem. Phys. 1985, 82, 284.
[50] P. J. Hay, W. R. Wadt, J. Chem. Phys. 1985, 82, 299.
[51] S. Miertus, E. Scrocco, J. Tomasi, Chem. Phys. 1981, 55, 117.
SUPPORTING INFORMATION
Additional supporting information may be found online
in the Supporting Information section at the end of this
article.
How to cite this article: Tabrizi L, Romanova J.
Antiproliferative Activity of Gold(I) N-Heterocyclic
Carbene and Triphenylphosphine Complexes with
Ibuprofen Derivatives as Effective Enzyme
Inhibitors. Appl Organometal Chem. 2020;e5618.
https://doi.org/10.1002/aoc.5618