Microwave-assisted synthesis of new selenazole derivatives with antiproliferative activity

Article abstract of DOI:10.3390/molecules18044679

New aryl-hydrazinyl-1,3-selenazole and aroyl-hydrazonyl-1,3-selenazoles were synthesized via Hantzsch type condensation reactions of selenosemicarbazides with α-halogenocarbonyl derivatives, under classical versus microwave heating conditions. Excellent y

Full text of DOI:10.3390/molecules18044679

Molecules 2013, 18, 4679-4688; doi:10.3390/molecules18044679
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molecules
ISSN 1420-3049
www.mdpi.com/journal/molecules
Article
Microwave-Assisted Synthesis of New Selenazole Derivatives
with Antiproliferative Activity
Adriana Ignat (Grozav) 1,*, Luiza Gaina 2,*, Victor Kuete 3, Luminita Silaghi-Dumitrescu 2,
Thomas Efferth 3 and Valentin Zaharia 1
1
Faculty of Pharmacy, “Iuliu Hatieganu” University of Medicine and Pharmacy, RO-400012,
Victor Babes 41, Cluj-Napoca, Romania; E-Mail: vzaharia@umfcluj.ro
2
Faculty of Chemistry and Chemical Engineering, “Babes Bolyai” University RO-400028,
Arany Janos 11, Cluj-Napoca, Romania; E-Mail: lusi@chem.ubbcluj.ro
3
Department of Pharmaceutical Biology, Institute of Pharmacy and Biochemistry, University of Mainz,
Staudinger Weg 5, 55128 Mainz, Germany; E-Mails: kuetevictor@yahoo.fr (V.K.);
efferth@uni-mainz.de (T.F.)
* Authors to whom correspondence should be addressed; E-Mails: adriana.ignat@umfcluj.ro (A.I.);
gluiza@chem.ubbcluj.ro (L.G.); Tel.: +40-264-594-148 (A.I.); +40-264-593-833 (L.G.);
Fax: +40-264-590-818 (L.G.).
Received: 11 March 2013; in revised form: 12 April 2013 / Accepted: 17 April 2013 /
Published: 19 April 2013
Abstract: New aryl-hydrazinyl-1,3-selenazole and aroyl-hydrazonyl-1,3-selenazoles were
synthesized via Hantzsch type condensation reactions of selenosemicarbazides with
α-halogenocarbonyl derivatives, under classical versus microwave heating conditions.
Excellent yields and shorter reaction times were obtained under irradiation conditions. The
structures of the synthesized compounds were assigned based on spectroscopic data
1
(FT-IR, H-NMR), MS and elemental analysis. Selenazole derivatives were screened for
their anti-proliferative effects against two leukemia cell lines (CCRF-CEM and HL60) and
three carcinoma cell lines (MDA-MB231, HCT116 and U87MG).
Keywords: selenazole; microwave assisted synthesis; cytotoxicity

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1. Introduction
Selenium is an essential element for organisms, but its beneficial effects on human health are
strongly dependent on concentration and on chemical form. The ingestion of foodstuffs with an
elevated selenium content can induce toxicity [1], while a low concentration of Se leads to a deficient
status [2].
In the last decade various organic selenium derivatives have been synthesized and tested for their
biological properties such as free radical scavengers [3–6], superoxide anion-scavenging activity [7],
inhibitors for different types of cancer cell proliferation [8–13], antioxidant activity [14–16] and
anti-inflammatory activity or inhibitory effects on microglial activation [17]. Besides the beneficial
effects, the toxic effects of selenium derivatives are well known; for example, the mutagenic effect
induced by the sodium selenite in the yeast Saccharomyces cerevisiae is associated with the ability to
act as an oxidizing agent producing superoxide and oxidative damage to DNA [18]. The genotoxic and
cytotoxic effects of organoselonium derivatives in human leukocyte cells and V79 Chinese lung
fibroblast cells can be associated to the pro-oxidant activity exhibited by selenium compounds when
used in relatively high concentrations [19,20].
A literature survey reveals that the Hantzsch condensation (with changes in reaction conditions or
catalysts) [21] appeared to be most frequently employed protocol for the synthesis of 1,3-selenazole
derivatives. In our previous work, the lipophilicity and anticancer activity of a number of selenazole
derivatives were investigated to better understand the correlation between drug delivery and
permeation across a biological membrane [22–24]. Continuing our effort in the synthesis and in the
characterization of the biological activity of new selenazole derivatives, we describe here the results of
our investigations regarding the anti-proliferative effects against two leukemia cell lines and three
carcinoma cell lines. To improve the reaction conditions, and encouraged by our previous results [25–27],
microwave-assisted synthesis was used. The most important advantages induced by microwaves in
organic synthesis consist in reduced reaction times, high yields and enhanced reaction rates [28].
2. Results and Discussion
The new arylidenehydrazinoselenazoles 3a–e and aroylhydrazinoselenazoles 5a–c were prepared
via Hantzsch condensation reactions of a selenosemicarbazone or benzoylselenosemicarbazide
with a series of α-halocarbonyl derivatives. Some of the starting materials, namely aryliden-
selenosemicarbazones 1–2 and p-methoxybenzoylselenosemicarbazide 4, were obtained by the
reaction of the corresponding aromatic carbaldehydes or methoxybenzoyl chloride with
selenosemicarbazide (Scheme 1). Moderate yields were obtained using the classical reaction
conditions, regardless of the various solvents tested (ethanol, acetone), and decomposition was
observed when the reaction mixture was refluxed. To improve the yields and the reaction time,
microwave irradiation was used instead of stirring the reaction mixture at room temperature.
Experiments were therefore conducted at different temperatures (40 C, 60 C or 90 C) and
irradiation times (30', 60' and 90' respectively) to identify the optimal synthesis conditions. The best
yields were obtained after 60 min of microwave irradiation at 60 C inside the reaction vessel
(temperatures above 90 C cause decomposition of the reaction products).

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Scheme 1. Synthesis of 1,3-selenazole derivatives.
Comp.
R1
p-MeO-C6H4 COOEt
p-MeO-C6H4 Me
p-MeO-C6H4 CH2Cl
R2
R3
H
X
Comp.
1
R1
R4
-
X
-
3a
3b
3c
3d
3e
6a
6b
6c
6d
6e
p-Cl-C6H4
COMe
H
2
p-MeO-C6H4
-
-
5a
5b
5c
-
-
-
-
-
-
COOEt
COMe
H
-
p-Cl-C6H4
Me
COOEt
COOEt
Me
COMe
H
-
p-Cl-C6H4
-
-
-
-
-
-
H
Br
Cl
Cl
Cl
Br
7a
7b
7c
COOEt
COMe
H
Br
Cl
Cl
COMe
H
CH2Cl
Me
COMe
H
COOEt
A comparison of the two alternative techniques (see Table 1), microwave irradiation and the
reaction at room temperature, emphasizes the advantages of microwave-assisted synthesis, which
affords almost quantitative reaction yields in much shorter reaction times.
Table 1. Comparative yields in the synthesis of selenazole derivatives, under microwave
irradiation and without heating.
Compounds
Yield (%) MW a
Yield (%) b
3a
93
52
3b 3c 3d 3e 5a 5b 5c
92 95 94 91 94 93 87
51 56 56 60 57 63 67
a W irradiation, power P = 200 W, time 60 min; b Without heating, room temperature, time 1,440 min.
The structures of the newly-synthesized compounds were confirmed by their 1H-NMR, MS and FT-
1
IR spectra. In the H-NMR spectra of selenazoles 3a–e the most deshielded signal is a singlet around
8.1–8.9 ppm, assigned to the azomethine proton (CH=N). Other characteristic signals for compounds
3a–e and 5a–c are the two doublets generated by the aromatic protons from the phenyl ring. For
example, these signals appear at 6.99 ppm, 7.66 ppm in the spectrum of selenazole 3a, at 6.99 ppm,
7.68 ppm for selenazole 3b, and 7.03 ppm, 7.95 ppm for selenazole 5a.

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The typical abundances for selenium isotopes 76Se(9.37%), 77Se(7.63%), 78Se(23.77%), 80Se(49.61%)
and 82Se(8.73%) [29,30] are present in the EIMS spectra. The molecular ion, accompanied by the
isotopic peaks confirms the molecular weight of the selenazole derivatives [i.e., in the EIMS spectra
for compound 5b, all the isotopic peaks for selenium are present, 351(78Se), 350(77Se), 349(76Se),
353 (80Se), 355 (82Se)].
The synthesized compounds were screened for their anti-proliferative effects against two leukemia
cell lines, CCRF-CEM and HL60, and three carcinoma cell lines MDA-MB231, HCT116 and
U87MG, in a protocol employing the resazurin assay. The cut-off point for compounds exhibiting
good cytotoxic properties is considered as 10 µM for the IC50 value following incubation between
48 and 72 h [31]. Values below this threshold were recorded with all studied compounds against the
leukemia CCRF-CEM, showing that they could be useful in the development of anticancer compounds
for this cell line. Additionally, compounds with the IC50 values closer to 10 µM (3e - 12.86 µM, 5c -
11.94 µM and 4 - 10.62 µM) could also be suggested as useful cytotoxic compounds against leukaemia
HL 60 cells. However, none of the compounds were as active as the reference drug doxorubicin.
Although no significant anti-proliferative effects were noted against the three studied adherent cell
lines, MDA-MB231, HCT116 and U87 MG, most of the compounds were active - with the IC50 values
below 50 µM in the majority of the cases (Table 2).
Table 2. IC50 values of the newly-synthesized compounds, versus doxorubicin.
Cell lines and IC50 values (µM)
Compounds
CCRF-CEM
6.36 ± 0.66
8.87 ± 2.52
5.11 ± 0.30
9.97 ± 1.58
8.40 ± 2.15
6.88 ± 1.53
8.33 ± 2.03
6.43 ± 0.96
5.67 ± 3.87
0.20 ± 0.06
HL60
MDA-MB231
>113.31
HCT116
>113.31
U87MG
>113.31
3a
48.44 ± 11.14
14.42 ± 234.31
27.67 ± 8.45
17.24 ± 1.66
12.86 ± 1.99
10.62 ± 0.88
29.88 ± 0.17
13.23 ± 0.12
11.94 ± 0.72
0.73 ± 0.20
3b
72.60 ± 47.56
85.24 ± 6.00
42.68 ± 1.18
65.72 ± 0.37
21.98 ± 0.63
61.19 ± 4.86
16.90 ± 4.55
29.19 ± 1.92
1.10 ± 0.28
53.37 ± 8.67
35.96 ± 4.17
35.13 ± 3.77
46.14 ± 0.97
23.51 ± 0.86
24.99 ± 2.58
22.25 ± 1.66
34.66 ± 3.21
1.41 ± 0.29
66.53 ± 6.36
65.41 ± 0.47
30.32 ± 1.08
59.12 ± 5.97
27.56 ± 10.02
29.80 ± 1.68
20.95 ± 1.62
25.22 ± 7.23
1.06 ± 0.15
3c
3d
3e
4
5a
5b
5c
Doxorubicin
3. Experimental
3.1. General
All chemicals were obtained from standard commercial sources unless otherwise indicated.
Compounds 1, 2, and 4 were prepared according to literature procedures [32,33]. Microwave irradiation
was performed in a CEM Discover LabMate reactor. Melting points were measured with an Electrothermal
1
IA 9200 apparatus, and are uncorrected values. H-NMR spectra were recorded in acetone-d6 (locked
to Me4Si) using a 300 MHz or 400 MHz Bruker Avance NMR spectrometer. FT-IR spectra were
recorded using a Bruker Vector 22 spectrometer. Elemental analysis was carried out on a Vario EL III
instrument. The mass spectra were recorded on a Shimadzu QP 2010 Plus GC-MS instrument.

Molecules 2013, 18
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3.2. General Procedure for the Preparation of Arylhydrazinoselenazoles 3a–e
(a) A solution of α-halocarbonyl derivative (2 mmol) in anhydrous acetone (5 mL) was added to a
solution of benzylidenehydrazinecarboselenoamide derivative (2 mmol) in DMF (5 mL). The reaction
mixture was stirred at room temperature for 24 h and then neutralized at pH = 7 with NaHCO3 aqueous
solution (10%).. The precipitate was filtered and then recrystallized from ethanol.
(b) A solution of α-halocarbonyl derivative (2 mmol) in anhydrous acetone (5 mL) was added to a
solution of benzylidenehydrazinecarboselenoamide derivative (2 mmol) in DMF (5 mL). The reaction
mixture was introduced in a microwave reaction vessel, which was then sealed and subjected to
microwave irradiation. The reaction mixture was subsequently neutralized at pH = 7 with NaHCO3
aqueous solution (10%). The obtained precipitate was filtered and then recrystallized from ethanol.
Experimental parameters for all derivatives are listed in Table 1.
(E)-Ethyl 2-[2-(4-methoxybenzylidene)hydrazinyl]-1,3-selenazole-4-carboxylate (3a). White-yellowish
crystals; yields: 36.7 mg, 52% (method a), 65.6 mg, 93% (method b); m.p. 216–217 °C; IR (KBr ν
cm−1): 3181 (νNH), 3113 (νCH), 1714 (νCOester), 1612 (νC=N), 1578, 1551, 1512 (νC=Caromatic); EIMS (m/z):
1
3
355/353, 351/350, 349 (M+), 307, 134 (100%);. H-NMR (300 MHz) δ: 1.31 (t, 3H, CH3, J = 7 Hz),
3.84 (s, 3H, OCH3), 4.26 (q, 2H, CH2, 3J = 7 Hz), 6.99 (d, 2H, 3J = 8.7 Hz), 7.66 (d, 2H, 3J = 8.7 Hz),
8.13 (s, 1H, CH), 8.18 (s, 1H, CH-Se); Anal. calcd. for C14H15N3O3Se: C 47.74, H 4.29, N 11.93, O
13.63, Se, 22.42; found: C 47.76, H 4.25, N 11.98, O 13.54.
(E)-1-[2-(2-(4-Methoxybenzylidene)hydrazinyl)-4-methyl-1,3-selenazol-5-yl]ethanone (3b). Brown
crystals; yields: 34.3 mg, 51% (method a), 62 mg, 92% (method b); m.p. 209–210 °C; IR (KBr ν
cm−1): 3184 (νNH), 3030 (νCH), 1699 (νCOcetone), 1614 (νC=N), 1575, 1550, 1511 (νC=Caromatic); EIMS
1
(m/z): 339/337, 335/334, 333 (M+), 294 (100%); H-NMR (300 MHz) δ: 2.40 (s, 3H, CH3), 2.49 (s,
3H, CH3), 3.84 (s, 3H, CH3), 6.99 (d, 2H, 3J = 8.7 Hz), 7.68 (d, 2H, 3J = 8.7 Hz), 8.19 (s, 1H, CH=N);
Anal. calcd for C14H15N3O2Se: C 50.01, H 4.50, N 12.50, O 9.52, Se 23.48; found: C 50.04, H 4.52, N
12.51, O 9.46.
(E)-4-(Chloromethyl)-2-[2-(4-methoxybenzylidene)hydrazinyl]-1,3-selenazole (3c). White crystals;
yields: 36.7 mg, 56% (method a), 62.4 mg, 95% (method b); m.p. 183–184 °C; IR (KBr ν cm−1): 3182
(νNH), 3058 (νCH), 1610 (νC=N), 1576, 1551, 1510 (νC=Caromatic); EIMS (m/z):331/329, 327/326, 325
(M+), 294, 134 (100%); 1H-NMR (300 MHz) δ: 3.83 (s, 3H, CH3), 4.5 (s, 2H, CH2Cl), 6.98 (d, 2H, 3J
3
= 8.7 Hz), 7.27 (s, 1H, Se-CH), 7.64 (d, 2H, J = 8.7 Hz), 8.10 (s, 1H, CH=N); Anal. calcd for
C12H12ClN3OSe: C 43.85, H 3.68, Cl 10.79, N 12.79, O 4.87, Se 24.03; found: C 43.87, H 3.69, N
12.81, O 4.82.
(E)-1-[2-(2-(4-Chlorobenzylidene)hydrazinyl)-4-methyl-1,3-selenazol-5-yl]ethanone (3d). Brown
crystals; yields: 38.1 mg, 56% (method a), 64 mg, 94% (method b); m.p 179–180 °C; IR (KBr ν cm−1):
3184 (νNH), 2993 (νCH), 1703 (νCO cetone), 1613 (νC=N), 1577, 1551, 1511 (νC=Caromatic); EIMS (m/z):
343/341, 339/338, 337 (M+), 298, 188, 138 (100); 1H-NMR (300 MHz) δ: 2.41 (s, 3H, CH3), 2.5 (s, 3H,
3
3
CH3), 7.42 (d, 2H, J = 7.3 Hz), 7.7(d, 2H, J = 7.3 Hz), 8.14 (s, 1H, CH=N). Anal. calcd for

Molecules 2013, 18
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C13H12ClN3OSe: C 45.83, H 3.55, Cl, 10.41, N 12.33, O 4.70, Se, 23.18; found: C 45.86, H 3.58, N
12.35, O 4.62.
(E)-Ethyl 2-[2-(4-chlorobenzylidene)hydrazinyl]-1,3-selenazole-4-carboxylate (3e). White-yellowish
crystals; yields: 42.8 mg, 60% (method a), 64.9 mg 91% (method b); m.p. 240–241 °C; IR (KBr ν
cm−1): 3182 (νNH), 3002 (νCH), 1722 (νCOester), 1614 (νC=N), 1576, 1550, 1512 (νC=Caromatic); EIMS (m/z):
1
359/357(100%), 355/354, 325 (M+), 311, 246, 138, 111; H-NMR (300 MHz) δ : 1.24 (t, 3H, CH3,
3J = 7 Hz), 4.16 (q, 2H, CH2, 3J = 7 Hz), 7.53 ppm (d, 2H, 3J = 7.6 Hz), 7.97 (d, 2H, 3J = 7.6 Hz), 8.13
(s, 1H, CH), 8.33 (s, 1H, CH-Se). Anal. calcd for C13H12ClN3O2Se: C 43.78, H 3.39, Cl, 9.94; N 11.78,
O 8.97, Se, 22.14; found: C 43.80, H 3.41, N 11.79, O 8.93.
3.3. General Procedure for the Preparation of Aroylhydrazinoselenazoles 5a–c
(a) A solution of α-halogenocarbonyl derivative (2 mmol) in anhydrous acetone (5 mL) was added
to a solution of 2-(4-methoxybenzoyl)hydrazinecarboselenoamide 4 (54.7mg, 2 mmol) in DMF (5 mL).
The reaction mixture was stirred at room temperature for 24 h and then neutralized at pH = 7 with
NaHCO3 aqueous solution (10%). The precipitate was filtered and then recrystallized from ethanol.
(b) A solution of α-halogenocarbonyl derivative (2 mmol) in anhydrous acetone (5 mL) was added
to a solution of 2-(4-methoxybenzoyl)hydrazinecarboselenoamide 4 (54.7mg, 2 mmol) in DMF (5 mL).
The reaction mixture was introduced in a microwave reaction vessel, which was then sealed and
subjected to microvawe irradiation. The reaction mixture was subsequently neutralized at pH = 7 with
NaHCO3 aqueous solution (10%). The obtained precipitate was filtered and then recrystallized from
ethanol. Experimental parameters for all derivatives are listed in Table 1.
Ethyl 2-[2-(4-methoxybenzoyl)hydrazinyl]-4-methyl-1,3-selenazole-5-carboxylate (5a). White crystals;
yields: 43.6 mg, 57% (method a), 72 mg, 94% (method b); m.p. 177–178 °C; IR (KBr ν cm−1): 3412,
3176 (νNH), 2982, 2838 (νCH), 1700 (νCOester), 1631 (νCOamide), 1587, 1531 (νC=Caromatic); EIMS (m/z):
385/383, 381/380, 379 (M+), 135 (100%); 1H-NMR (400 MHz) δ: 1.23 (t, 3H, CH3, 3J = 7 Hz), 2.43 (s,
3H, CH3), 3.84 (s, 3H, CH3), 4.16 (q, 2H, CH2, 3J = 7 Hz), 7.03 ppm (d, 2H, 3J = 8.2 Hz), 7.95 (d, 2H,
3J = 8.2 Hz); Anal. calcd for C15H17N3O4Se: C 47.13, H 4.48, N 10.99, O 16.74, Se, 20.66; found: C
47.15, H 4.50, N 11.01, O 16.23.
N'-(5-Acetyl-4-methyl-1,3-selenazol-2-yl)-4-methoxybenzohydrazide (5b). White crystals; yields: 44
mg, 63% (method a), 65.6 mg, 93% (method b); m.p. 186–187 °C; IR (KBr ν cm−1): 3412, 3211 (νNH),
3097, 2946 (νCH), 1696 (νCO cetone), 1635 (νCO amide), 1596, 1532 (νC=Caromatic); EIMS (m/z): 355/353,
1
351/350, 349 (M+), 135 (100%); H-NMR (300 MHz) δ: 2.4 (s, 3H, CH3), 2.46 (s, 3H, CH3), 3.89
3
3
(s, 3H, CH3), 7.05 (d, 2H, J = 8.5 Hz), 7.96 (d, 2H, J = 8.5 Hz); Anal. calcd. for C14H15N3O3Se:
C 47.74, H 4.29, N 11.93, O 13.63, Se 22.42; found: C 47.76, H 4.31, N 11.95, O 13.54.
4-Methoxy-N'-(4-methyl-1,3-selenazol-2-yl)benzohydrazide (5c). White crystals; yields: 41.6 mg, 67%
(method a), 54.1 mg 87% (method b); m.p. 265–266 °C; IR (KBr ν cm−1): 3399, 3208 (νNH), 3093,
2944 (νCH), 1633 (νCO amidă), 1591, 1526 (νC=Caromatic); EIMS (m/z): 313/311, 309/308, 307 (M+), 135
(100%). 1H-NMR (400 MHz); δ: 2.4 (s, 3H, CH3), 3.8 (s, 3H, CH3), 7.05 (d, 2H, 3J = 8.5 Hz), 7.12(s, 1H,

Molecules 2013, 18
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Se-CH), 7.95 (d, 2H, 3J = 8.5 Hz); Anal. calcd. for C12H13N3O2Se: C 46.46, H 4.22, N 13.55, O 10.32,
Se 25.45; found: C 46.43, H 4.25, N 13.53, O 10.30.
3.4. Cytotoxicity Assay
The resazurin reduction assay [34] was performed to assess the cytotoxicity of the newly-
synthesized compounds towards various sensitive and resistant cancer cell lines, including the
leukemia CCRF-CEM, HL60, breast MDA-MB231, colon HCT116 and glioblastoma U87MG. The
assay is based on the reduction of the indicator dye, resazurin, to the highly fluorescent resorufin by
viable cells. Non-viable cells rapidly lose their metabolic capacity to reduce resazurin and, thus, do not
produce fluorescent signals anymore. Briefly, adherent cells were detached by treatment with 0.25%
trypsin/EDTA (Invitrogen, Darmstadt Germany) and an aliquot of 1 × 104 cells was placed in each
well of a 96-well cell culture plate (Thermo Scientific, Langenselbold, Germany) in a total volume of
200 µL. Cells were allowed to attach overnight and then were treated with different concentrations of
compounds. For suspension cells, aliquots of 2 × 104 cells per well were seeded in 96-well-plates in a
total volume of 100 µL. The studied compound was immediately added in varying concentrations in an
additional 100 µL of culture medium to obtain a total volume of 200 µL/well. After 72 h, resazurin
(Sigma-Aldrich, Schnelldorf, Germany) (20 µL, 0.01% w/v) in ddH2O was added to each well and the
plates were incubated at 37 °C for 4 h. Fluorescence was measured on an Infinite M2000 ProTM plate
reader (Tecan, Crailsheim, Germany) using an excitation wavelength of 544 nm and an emission
wavelength of 590 nm. Each assay was done at least twice with six replicates each. The viability was
evaluated based on a comparison with untreated cells. IC50 values represent the compound
concentrations required to inhibit 50% of cell proliferation and were calculated from a calibration
curve by linear regression using Microsoft Excel.
4. Conclusions
In conclusion, we have carried out, in high yield and short reaction times, the synthesis of eight new
1,3-selenazole derivatives by microwave irradiation. The new 1,3-selenazoles were investigated for
anti-proliferative effects against two leukemia cell lines (CCRF-CEM and HL60) and three carcinoma
cell lines (MDA-MB231, HCT116 and U87MG) and show moderate biological in vitro activity.
Acknowledgement
Financial support from the Romanian Ministry of Education and Research (grant CNCSIS PNII
142198-1 and 11/RO-CH-RSRP/01.01.2013; grant ID PCCE 140/2008; grant UMF Cluj-Napoca
27020/22/15.11.2011) is greatly acknowledged. Victor Kuete is very grateful to the Alexander von
Humboldt foundation for an 18 months fellowship in Germany through the “Georg Foster Research
Fellowship for Experienced Researcher” program for funding this work.
Conflict of Interest
The authors declare no conflict of interest.

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References
1. Muller, D.; Desel, H. Acute selenium poisoning by paradise nuts (Lecythis ollaria). Hum. Exp.
Toxicol. 2010, 29, 431–434.
2. Klapec, T.; Mandić, M.L.; Grgić, J.; Primorac, L.; Ikić, M.; Lovrić, T.; Grgić, Z.; Herceg, Z.
Daily dietary intake of selenium in eastern Croatia. Sci. Total Environ. 1998, 217, 127–136.
3. Nishina, A.; Kimura, H.; Kozawa, K.; Sommen, G.L.; Nakamura, T.; Heimgartner, H.; Koketsu,
M.; Furukawa, S. A superoxide anion-scavenger, 1,3-selenazolidin-4-one suppresses serum
deprivation-induced apoptosis in PC12 cells by activating MAP kinase. Toxicol. Appl. Pharmacol.
2011, 257, 388–395.
4. Sekiguchi, A.; Nishina, A.; Kimura, H.; Fukumoto, R.; Kogami, M.; Ishihara, H.; Koketsu, M.
Bis-(2-amino-5-selenazoyl) ketone as a superoxide anion-scavenger. Pharm. Bull. 2006, 29,
1404–1407.
5. Takahashi, H.; Nishina, A.; Kimura, H.; Motoki, K.; Koketsu, M.; Ishihara, H. Tertiary
selenoamide compounds are useful superoxide radical scavengers in vitro. Eur. J. Pharm. Sci.
2004, 23, 207–211.
6. Takahashi, H.; Nishina, A.; Fukumoto, R.; Kimura, H.; Koketsu, M.; Ishihara, H. Selenoureas and
thioureas are effective superoxide radical scavengers in vitro. Life Sci. 2005, 76, 2185–2192.
7. Takahashi, H.; Nishina, A.; Fukumoto, R.; Kimura, H.; Koketsu, M.; Ishihara, H. Selenocarbamates
are effective superoxide anion scavengers in vitro. Eur. J. Pharm. Sci. 2005, 24, 291–295.
8. Bijian, K.; Zhang, Z.; Xu, B.; Jie, S.; Chen, B.; Wan, S.; Wu, J.; Jiang, T.; Alaoui-Jamali, M.A.
Synthesis and biological activity of novel organoselenium derivatives targeting multiple kinases
and capable of inhibiting cancer progression to metastases. Eur. J. Med. Chem. 2012, 48, 143–152.
9. Madhunapantula, S.V.; Desai, D.; Sharma, A.; Huh, S.J.; Amin, S.; Robertson, G.P. PBISe,
a novel selenium-containing drug for the treatment of malignant melanoma. Mol. Cancer Ther.
2008, 7, 1297–308.
10. Desai, D.; Madhunapantula, S.V.; Gowdahalli, K.; Sharma, A.; Chandagaludoreswamy, R.;
El-Bayoumy, K.; Robertson, G.P.; Amin, S. Synthesis and characterization of a novel iNOS/Akt
inhibitor Se,Se0-1,4-phenylenebis(1,2-ethanediyl)bisisoselenourea (PBISe)—against colon
cancer. Bioorg. Med. Chem. Lett. 2010, 20, 2038–2043.
11. Xing, F.; Li, S.; Ge X.; Wang, C.; Zeng, H.; Li, D.; Dong. L. The inhibitory effect of a novel
organoselenium compound BBSKE on the tongue cancer Tca8113 in vitro and in vivo.
Oral Oncol. 2008, 44, 963–969.
12. Wang, L.; Yang, Z.; Fu, J.; Yin, H.; Xiong, K.; Tan, Q.; Jin, H.; Li, J.; Wang, T.; Tang, W.; et al.
Ethaselen: a potent mammalian thioredoxin reductase 1 inhibitor and novel organoselenium
anticancer agent. Free Radic. Biol. Med. 2012, 52, 898–908.
13. Terazawa, R.; Garud, D.R.; Hamada, N.; Fujita, Y.; Itoh, T.; Nozawa, Y.; Nakane, K.; Deguchi, T.;
Koketsu, M.; Ito, M. Identification of organoselenium compounds that possess chemopreventive
properties in human prostate cancer LNCaP cells. Bioorg. Med. Chem. 2010, 18, 7001–7008.
14. Merino-Montiel, P.; Maza, S.; Martos, S.; LOpez, O.; Maya, I.; Fernandez-Bolanos, J.G.
Synthesis and antioxidant activity of O-alkyl selenocarbamates, selenoureas and selenohydantoins.
Eur. J. Pharm. Sci. 2013, 48, 582–592.

Molecules 2013, 18
4687
15. Barbieri Gerzson, M.F.; Victoria, F.N.; Radatz, C.S.; de Gomes, M.G.; Boeira, S.P.; Jacob, R.G.;
Alves, D.; Jesse, C.R.; Savegnago, L. In vitro antioxidant activity and in vivo antidepressant-like
effect of α-(phenylselanyl) acetophenone in mice. Pharmacol. Biochem. Behav. 2012, 102, 21–29.
16. Acker, C.I.; Brandão, R.; Rodrigues Rosário, A.; Nogueira, C.W. Antioxidant effect of
alkynylselenoalcohol compounds on liver and brain of rats in vitro. Environ. Toxicol. Phar. 2009,
28, 280–287.
17. Nam, K.N.; Koketsu, M.; Lee, E.H. 5-Chloroacetyl-2-amino-1,3-selenazoles attenuate microglial
inflammatory responses through NF-κB inhibition. Eur. J. Pharmacol. 2008, 589, 53–57.
18. Letavayova, L.; Vlasakova, D.; Spallholz, J.E.; Brozmanova J.; Chovanec, M. Toxicity and
mutagenicity of selenium compounds in Saccharomyces cerevisiae. Mutat. Res. 2008, 638, 1–10.
19. Santos, D.B.; Schiar, V.P.P.; Ribeiro, M.C.P.; Schwab, R.S.; Meinerz, D.F.; Allebrandt, J.;
Rocha, J.B.T.; Nogueira, C.W.; Aschner, M.; Barbosa, N.B.V. Genotoxicity of organoselenium
compounds in human leukocytes in vitro. Mutat. Res. 2009, 676, 21–26.
20. Rosa, R.M.; Picada, J.N.; Saffi, J.; Henriques, J.A.P. Cytotoxic, genotoxic, and mutagenic effects
of diphenyl diselenide in Chinese hamster lung fibroblasts. Mutat. Res. 2007, 628, 87–98.
21. Tao, H.; Weng, Y.; Zhuo, Z.; Chang, G.; Urbatsch, L. I.; Zhang, Q. Design and synthesis of
Selenazole-containing peptides for cocrystallization with P-glycoprotein. ChemBioChem 2011,
12, 868-873.
22. Cozma, A.; Vlase, L.; Ignat, A.; Zaharia, V.; Gocan, S.; Marutoiu, C.; Fodor, A. Lipophilicity
study of new selenazole derivatives by RP-HPLC. Rev. Chim. (Bucharest) 2012, 63, 651–655.
23. Cozma, A.; Zaharia, V.; Ignat, A.; Gocan, S.; Grinberg, N. Prediction of the lipophilicity of nine
new synthesized selenazoly and three aroyl–hydrazinoselenazoles derivatives by reversed-phase
high performance thin-layer chromatography. J. Chromatogr. Sci. 2012, 50, 157–161.
24. Zaharia, V.; Ignat, A.; Ngameni, B.; Kuete, V.; Moungang, M.L.; Fokunang, C.N.; Vasilescu, M.;
Palibroda, N.; Cristea, C.; Silaghi-Dumitrescu, L.; et al. Heterocycles 23: Synthesis,
characterization and anticancer activity of new hydrazinoselenazole derivatives. Med. Chem. Res.
2013, 558, doi:10.1007/s00044-013-0558-8.
25. Gaina, L.; Gal, E.; Mataranga-Popa, L.; Porumb, D.; Nicolescu, A.; Cristea, C.; Silaghi-Dumitrescu,
L. Synthesis, structural investigations, and DFT calculations on novel 3-(1,3-dioxan-2-yl)-10-methyl-
10H-phenothiazine derivatives with fluorescence properties. Tetrahedron 2011, 68, 2465–2470.
26. Gaina, L.; Porumb, D.; Silaghi-Dumitrescu, L.; Cristea, C.; Silaghi-Dumitrescu, L. On the
microwave-assisted synthesis of acylphenothiazine derivatives-Experiment versus theory synergism.
Can. J. Chem. 2010, 88, 42–49.
27. Gaina, L.; Cristea, C.; Moldovan, C.; Porumb, D.; Surducan, E.; Deleanu, C.; Mahamoud, A.;
Barbe, J.; Silberg, I.A. Microwave-assisted synthesis of phenothiazine and quinoline derivatives.
Int. J. Mol. Sci. 2007, 8, 70–80.
28. Vaibhav, P. M.; Van der Eycken, E. V. Microwave-assisted C-C bond forming cross-coupling
reactions: an overview. Chem. Soc. Rev. 2011, 40, 4925–4936.
29. Audi, G.; Wapstra, A.H. The 1993 atomic mass evaluation. Nucl. Phys. A 1993, 565, 1–65.
30. Audi, G.; Wapstra, A.H. The 1995 update to the atomic mass evaluation. Nucl. Phys. A 1995, 595,
409–480.

Molecules 2013, 18
4688
31. Brahemi, G.; Kona, F.R.; Fiasella, A.; Buac, D.; Soukupov, J.; Brancale, A.; Burger, A.M.;
Westwell, A.D. Exploring the structural requirements for inhibition of the ubiquitin E3 ligase
breast cancer associated protein 2 (BCA2) as a treatment for breast cancer. J. Med. Chem. 2010,
53, 2757–2765.
32. Wiles, D.M.; Suprunchuk, T. The C==S stretching vibration in the infrared spectra of some
thiosemicarbazones. II. Aldehyde thiosemicarbazones containing aromatic groups. Can. J. Chem.
1967, 45, 2258–2263.
33. Collard-Charon, C.; Renson, M. Synthèse des Sélénosemicarbazides Substituées III. Synthèse des
sélénosemicarbazides substituées en 1. Bull. Soc. Chim. Belg. 1962, 71, 554–562.
34. O’Brien, J.; Wilson, I.; Orton, T.; Pognan, F. Investigation of the Alamar Blue (resazurin)
fluorescent dye for the assessment of mammalian cell cytotoxicity. Eur. J. Biochem. 2000, 267,
5421–5426.
Sample Availability: Samples of the compounds 1, 2, 3a–e, 4, 5a–c are available from the author
A. Ignat (Grozav).
© 2013 by the authors; licensee MDPI, Basel, Switzerland. This article is an open access article
distributed under the terms and conditions of the Creative Commons Attribution license
(http://creativecommons.org/licenses/by/3.0/).