Synthesis and carbonic anhydrase inhibitory activities of new thienyl-substituted pyrazoline benzenesulfonamides

Article abstract of DOI:10.1080/14756366.2016.1181627

A series of new thienyl-substituted pyrazoline benzenesulfonamides were synthesized and their carbonic anhydrase (CA, EC 4.2.1.1) inhibitory activities were tested on the human (h) isoforms hCA I and hCA II. The inhibition constant (K_i) of thes

Full text of DOI:10.1080/14756366.2016.1181627

Journal of Enzyme Inhibition and Medicinal Chemistry
ISSN: 1475-6366 (Print) 1475-6374 (Online) Journal homepage: http://www.tandfonline.com/loi/ienz20
Synthesis and carbonic anhydrase inhibitory
activities of new thienyl-substituted pyrazoline
benzenesulfonamides
Ebru Mete, Birnur Comez, Halise Inci Gul, Ilhami Gulcin & Claudiu T. Supuran
To cite this article: Ebru Mete, Birnur Comez, Halise Inci Gul, Ilhami Gulcin & Claudiu T.
Supuran (2016): Synthesis and carbonic anhydrase inhibitory activities of new thienyl-
substituted pyrazoline benzenesulfonamides, Journal of Enzyme Inhibition and Medicinal
Chemistry, DOI: 10.1080/14756366.2016.1181627
To link to this article: http://dx.doi.org/10.1080/14756366.2016.1181627
Published online: 19 Jul 2016.
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2016 Informa UK Limited, trading as Taylor & Francis Group. DOI: 10.1080/14756366.2016.1181627
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RESEARCH ARTICLE
Synthesis and carbonic anhydrase inhibitory activities of new
thienyl-substituted pyrazoline benzenesulfonamides
Ebru Mete1, Birnur Comez2, Halise Inci Gul2, Ilhami Gulcin1,3, and Claudiu T. Supuran4
1Department of Chemistry, Faculty of Science, Ataturk University, Erzurum, Turkey, 2Department of Pharmaceutical Chemistry, Faculty of Pharmacy,
3
4
Ataturk University, Erzurum, Turkey, Department of Zoology, College of Science, King Saud University, Riyadh, Saudi Arabia, and Neurofarba
Department and Laboratorio di Chimica Bioinorganica, Polo Scientifico, Universita’ degli Studi di Firenze, Sesto Fiorentino (Firenze), Italy
Abstract
Keywords
A series of new thienyl-substituted pyrazoline benzenesulfonamides were synthesized and their
carbonic anhydrase (CA, EC 4.2.1.1) inhibitory activities were tested on the human (h) isoforms
hCA I and hCA II. The inhibition constant (Ki) of these sulfonamides were in the range of 232.16–
637.70 nM toward the slow cytosolic isozyme hCA I, and in the range of 342.07–455.80 nM
toward hCA II. Many of these compounds showed comparable inhibition with the reference
sulfonamide acetazolamide, a clinically used drug. As the sulfonamide CA inhibitors (CAIs) show
many therapeutic uses, these derivatives represent interesting examples of a novel class of such
derivatives.
Benzenesulfonamides, carbonic anhydrase,
pyrazoline, synthesis, thiophene
History
Received 6 April 2016
Revised 18 April 2016
Accepted 19 April 2016
Published online 19 July 2016
Introduction
having five-membered heterocycle system had better CA activity
than six-membered rings17. So, the insertion of the thiophene ring
into the chemical design can be a useful strategy to obtain
compounds with impressive bioactivity.
The aim of this study was to synthesize 4-aryl-5-(thiophen-2-
yl)-4,5-dihydro-1H-pyrazol-1-yl) benzenesulfonamides, 9–16,
which have pyrazoline, sulfonamide and thiophene pharmaco-
phores, to investigate their CA inhibitory activities.
Chalcones are open-chain flavonoids, being well-known inter-
mediates for synthesizing various heterocyclic compounds, which
are associated with an amazing range of biological activities1,2
.
Chalcones can be used as intermediate compounds for designing
and synthesizing pharmacologically active heterocyclic structures
such as pyrazolines. Pyrazolines have several biological activities
including anticancer, antiviral, antimicrobial and anti-inflamma-
tory activities3–6
.
Carbonic anhydrase (CA) is a superfamily of metalꢀloenzymes
that catalyzes the rapid conversion of CO2 to HCO3 and H+,
being involved in many biochemical processes7. CA isoforms are
found in a variety of tissues where they participate in several
important biological processes, such as acid–base balance,
respiration, carbon dioxide and ion transport, bone resorption,
ureagenesis, gluconeogenesis, lipogenesis and electrolyte secre-
tion7. Many CA isozymes involved in these processes are
important therapeutic targets with the potential to be inhibited/
activated for the treatment of a range of disorders, such as edema,
glaucoma, obesity, cancer, epilepsy, diuretics, antiepileptics,
anticancer and osteoporosis8–14. Sulfonamide derivatives, espe-
cially aromatic and heterocyclic sulfonamides when the sulfona-
mido group is unsubstituted15, are specific and potent carbonic
Materials and methods
Melting points were determined on Buchi 530 (Buchi
Labortechnik AG, Flawil, Switzerland). 1H NMR (400 MHz)
and 13C NMR (100 MHz) spectra were obtained using a Varian
Mercury Plus spectrometer (Varian Inc., Palo Alto, CA).
Chemical shifts (ꢀ) were reported in parts per million (ppm).
Liquid chromatography ion trap-time of flight tandem mass
spectrometer (Shimadzu, Kyoto, Japan) equipped with an
electrospray ionization (ESI) source, operating in both positive
and negative ionization mode. Shimadzu’s LCMS Solution
software was used for data analysis.
General procedure for the synthesis of chalcones (1–8)
anhydrase inhibitors (CAIs) and still attract much interest7–9
.
An aqueous solution of NaOH (10%, 10 mL) was added into the
ethanol (6 mL) solution of 2-thiophene carbaldehyde
p-Hydrazinobenzenesulfonamide itself or its condensation deriva-
tives with acetoacetic and levulinic acids had a definite inhibitory
activity on carbonic anhydrases when there was no substituent on
sulfonamido group16. It was reported that sulfonamide compounds
(20.0 mmol) and
a
suitable acetophenone (20.0 mmol)
(Scheme 1). The mixture was stirred overnight at room
temperature and it was then poured on ice-water (100 ml). The
mixture was neutralized with a solution of HCl (10%). The
colored precipitate formed was filtered and crystallized from
methanol–water (1–8). The yields of the chalcones were in the
range of 32–59% [1 (50%), 2 (43%), 3 (46%), 4 (55%), 5 (59%),
6 (44%), 7 (41%), 8 (32%)]18.
Address for correspondence: Assoc. Prof. Ebru Mete, Department of
Chemistry, Faculty of Science, Ataturk University, Erzurum, Turkey.
Tel: +90-442-2314436.
ebru25@atauni.edu.tr
Fax:
+90-442-2360948.
E-mail:

2
E. Mete et al.
J Enzyme Inhib Med Chem, Early Online: 1–5
R
O
O
O
N
i
ii
+
N
H
CH
3
S
S
S
R
R
Chalcones (1-8)
O
S
O
NH
2
Pyrazolines (9-16)
R: H for 1, 9; CH for 2, 10; CH O for 3, 11; Cl for 4, 12; F for 5, 13; Br for 6, 14; NO for 7, 15; OH for 8, 16.
3
3
2
+
(i) 10% aq NaOH, EtOH, 0-5 °C, 12 h; (ii) 4-hydrazinobenzenesulfonamide hydrochloride, EtOH/H , reflux 12 h.
Scheme 1. Synthesis of 1,3,5-trisubstituted pyrazoline-bearing benzenesulfonamides, 9–16.
General procedure for the synthesis of pyrazolines (9–16)
J ¼ 17.6, 4.0 Hz); 13C NMR (100 MHz, DMSO-d6, ppm)
ꢀ ¼ 161.0, 150.7, 146.9, 145.3, 133.8, 128.5, 127.7, 127.6,
126.22, 126.16, 124.9, 114.9, 112.9, 59.0, 56.0, 43.9; HRMS
(ESI-MS): calcd. for C20H20N3O3S2 [M + H]+ 414.0941; found
414.0925.
The mixture of a suitable chalcone (1.0 mmol) and 4-hydrazino
benzenesulfonamide hydrochloride (1.1 mmol) was dissolved in
ethanol, and then catalytic amount of glacial acetic acid was
added (Scheme 1). The mixture was refluxed for 12 h (9–16).
Reactions were followed by thin-layer chromotography (TLC).
After the reaction was stopped, some of the solvent was removed
under vacuum and the mixture was stirred for 12 h at room
temperature. The obtained solid was filtered, dried at room
temperature and crystallized from methanol–ether (9–16)6.
4-(3-(4-Chlorophenyl)-5-(thiophen-2-yl)-4,5-dihydro-1H-pyrazol-
1-yl)benzenesulfonamide (12)
1
M.p. 184–186 ꢁC. Yield: 41%. H NMR (400 MHz, DMSO-d6,
ppm) ꢀ ¼ 7.80 (d, 2H, J ¼ 8.6 Hz), 7.60 (d, 2H, J ¼ 8.8 Hz), 7.51
(d, 2H, J ¼ 8.8 Hz), 7.36 (d, 1H, J ¼ 5.1 Hz), 7.19 (d, 2H,
J ¼ 8.6 Hz), 7.14 (d, 1H, J ¼ 3.5 Hz), 7.04 (s, 2H, NH2), 6.93 (dd,
1H, J ¼ 5.1, 3.5 Hz), 6.01 (dd, 1H, J ¼ 11.6, 4.5 Hz), 3.91 (dd, 1H,
J ¼ 17.6, 11.6 Hz), 3.32 (dd, 1H, J ¼ 17.6, 4.5 Hz); 13C NMR
(100 MHz, DMSO-d6, ppm) ꢀ ¼ 149.6, 146.5, 144.9, 134.6, 134.5,
131.3, 129.5, 128.5, 127.7, 127.6, 126.35, 126.32, 113.3, 59.4,
43.6; HRMS (ESI-MS): calcd. for C19H17ClN3O2S2
[M + H]+ 418.0445; found 418.0443.
4-(3-Phenyl-5-(thiophen-2-yl)-4,5-dihydro-1H-pyrazol-1-yl)ben-
zenesulfonamide (9)
1
M.p. 207–209 ꢁC. Yield: 77%. H NMR (400 MHz, DMSO-d6,
ppm) ꢀ ¼ 7.79 (d, 2H, J ¼ 8.1 Hz), 7.60 (d, 2H, J ¼ 8.8 Hz), 7.47–
7.40 (m, 3H), 7.36 (d, 1H, J ¼ 5.0 Hz), 7.19 (d, 2H, J ¼ 8.8 Hz),
7.14 (d, 1H, J ¼ 3.4 Hz), 7.03 (s, 2H, NH2), 6.94 (dd, 1H, J ¼ 5.0,
3.4 Hz), 5.99 (dd, 1H, J ¼ 11.5, 4.7 Hz), 3.92 (dd, 1H, J ¼ 17.6,
11.5 Hz), 3.32 (dd, 1H, J ¼ 17.6, 4.7 Hz); 13C NMR (100 MHz,
DMSO-d6, ppm) ꢀ ¼ 150.7, 146.7, 145.2, 134.2, 132.4, 130.1,
129.4, 127.7, 127.6, 126.8, 126.3, 126.2, 113.2, 59.2, 43.7; HRMS
(ESI-MS): calcd. for C19H18N3O2S2 [M + H]+ 384.0835; found
384.0822.
4-(3-(4-Fluorophenyl)-5-(thiophen-2-yl)-4,5-dihydro-1H-pyrazol-
1-yl)benzenesulfonamide (13)
1
M.p. 200–202 ꢁC. Yield: 85%. H NMR (400 MHz, DMSO-d6,
ppm) ꢀ ¼ 7.84 (dd, 2H, J ¼ 8.8, 5.5 Hz), 7.60 (d, 2H, J ¼ 8.8 Hz),
7.36 (d, 1H, J ¼ 5.1 Hz), 7.28 (t, 2H, J ¼ 8.8 Hz), 7.18 (d, 2H,
J ¼ 8.8 Hz), 7.14 (d, 1H, J ¼ 3.2 Hz), 7.03 (s, 2H, NH2), 6.93 (dd,
1H, J ¼ 5.1, 3.2 Hz), 5.99 (dd, 1H, J ¼ 11.6, 4.5 Hz), 3.91 (dd, 1H,
J ¼ 17.6, 11.6 Hz), 3.31 (dd, 1H, J ¼ 17.6, 4.5 Hz); 13C NMR
(100 MHz, DMSO-d6, ppm) ꢀ ¼ 163.4 (d, 1J ¼ 247 Hz), 149.9,
146.7, 145.1, 134.3, 129.1, 129.0, 127.7, 127.6, 126.3, 126.2,
116.5 (d, 2J ¼ 22 Hz), 113.2, 59.3, 43.8; HRMS (ESI-MS): calcd.
for C19H17FN3O2S2 [M + H]+ 402.0741; found 402.0734.
4-(5-(Thiophen-2-yl)-3-(p-tolyl)-4,5-dihydro-1H-pyrazol-1-
yl)benzenesulfonamide (10)
1
M.p. 206–208 ꢁC. Yield: 66%. H NMR (400 MHz, DMSO-d6,
ppm) ꢀ ¼ 7.68 (d, 2H, J ¼ 8.6 Hz), 7.60 (d, 2H, J ¼ 8.4 Hz), 7.35
(d, 1H, J ¼ 5.0 Hz), 7.25 (d, 2H, J ¼ 8.4 Hz), 7.17 (d, 2H,
J ¼ 8.6 Hz), 7.13 (d, 1H, J ¼ 3.0 Hz), 7.03 (s, 2H, NH2), 6.93 (dd,
1H, J ¼ 5.0, 3.0 Hz), 5.96 (dd, 1H, J ¼ 11.3, 4.5 Hz), 3.89 (dd, 1H,
J ¼ 17.5, 11.3 Hz), 3.29 (dd, 1H, J ¼ 17.5, 4.5 Hz), 2.33 (s, 3H,
CH3); 13C NMR (100 MHz, DMSO-d6, ppm) ꢀ ¼ 150.8, 146.8,
145.2, 139.9, 134.0, 130.0, 129.6, 127.7, 127.6, 126.8, 126.26,
126.21, 113.1, 59.1, 43.8, 21.7; HRMS (ESI-MS): calcd. for
C20H20N3O2S2 [M + H]+ 398.0991; found 398.0984.
4-(3-(4-Bromophenyl)-5-(thiophen-2-yl)-4,5-dihydro-1H-pyrazol-
1-yl)benzenesulfonamide (14)
1
M.p. 197–199 ꢁC. Yield: 58%. H NMR (400 MHz, DMSO-d6,
ppm) ꢀ ¼ 7.73 (d, 2H, J ¼ 8.6 Hz), 7.64 (d, 2H, J ¼ 8.6 Hz), 7.60
(d, 2H, J ¼ 8.6 Hz), 7.36 (d, 1H, J ¼ 5.0 Hz), 7.19 (d, 2H,
J ¼ 8.6 Hz), 7.14 (d, 1H, J ¼ 3.4 Hz), 7.04 (s, 2H, NH2), 6.93 (dd,
1H, J ¼ 5.0, 3.4 Hz), 6.01 (dd, 1H, J ¼ 11.7, 4.4 Hz), 3.91 (dd, 1H,
J ¼ 17.6, 11.7 Hz), 3.29 (dd, 1H, J ¼ 17.6, 4.4 Hz); 13C NMR
(100 MHz, DMSO-d6, ppm) ꢀ ¼ 149.7, 146.5, 144.9, 134.5, 132.4,
131.6, 128.7, 127.7, 127.6, 126.4, 126.3, 123.3, 113.3, 59.3, 43.5;
4-(3-(4-Methoxyphenyl)-5-(thiophen-2-yl)-4,5-dihydro-1H-pyra-
zol-1-yl)benzenesulfonamide (11)
1
M.p. 219–221 ꢁC. Yield: 71%. H NMR (400 MHz, DMSO-d6,
ppm) ꢀ ¼ 7.73 (d, 2H, J ¼ 8.8 Hz), 7.58 (d, 2H, J ¼ 8.8 Hz), 7.35
(d, 1H, J ¼ 5.2 Hz), 7.16–7.12 (m, 3H), 7.01–6.99 (m, 4H), 6.93
(dd, 1H, J ¼ 5.2, 3.3 Hz), 5.94 (dd, 1H, J ¼ 11.6, 4.0 Hz), 3.88 (dd,
1H, J ¼ 17.6, 11.6 Hz), 3.79 (s, 3H, OCH3), 3.29 (dd, 1H,
HRMS
(ESI-MS):
calcd.
for
C19H17BrN3O2S2
[M + H]+ 461.9940; found 461.9929.

DOI: 10.1080/14756366.2016.1181627
New thienyl-substituted pyrazoline benzenesulfonamides
3
4-(3-(4-Nitrophenyl)-5-(thiophen-2-yl)-4,5-dihydro-1H-pyrazol-
1-yl)benzenesulfonamide (15)
spectrophotometrically at 595 nm during the purification steps
according to the Bradford method27. As reported previously,
bovine serum albumin was used as a standard protein. An activity
(%)–[benzenesulfonamides] graph was depicted to determine the
inhibitory effect of each benzenesulfonamides derivative. For Ki
values, three different concentrations of 9–16 were tested. NPA
was used as a substrate at five different concentrations, and
Lineweaver–Burk curves28 were drawn as described in previous
1
M.p. 209–211 ꢁC. Yield: 78%. H NMR (400 MHz, DMSO-d6,
ppm) ꢀ ¼ 8.27 (d, 2H, J ¼ 8.8 Hz), 8.02 (d, 2H, J ¼ 8.8 Hz), 7.64
(d, 2H, J ¼ 8.8 Hz), 7.38 (d, 1H, J ¼ 5.1 Hz), 7.26 (d, 2H,
J ¼ 8.8 Hz), 7.16 (d, 1H, J ¼ 3.1 Hz), 7.07 (s, 2H, NH2), 6.94 (dd,
1H, J ¼ 5.1, 3.1 Hz), 6.13 (dd, 1H, J ¼ 11.8, 4.6 Hz), 3.98 (dd, 1H,
J ¼ 17.7, 11.8 Hz), 3.40 (dd, 1H, J ¼ 17.7, 4.6 Hz); 13C NMR
(100 MHz, DMSO-d6, ppm) ꢀ ¼ 148.6, 147.8, 145.9, 144.6, 138.6,
135.2, 127.8, 127.7, 127.6, 126.6, 126.5, 124.7, 113.8, 59.7, 43.2;
HRMS (ESI-MS): calcd. for C19H17N4O4S2 [M + H]+ 429.0686;
found 429.0690.
studies29,30
.
Results and discussion
Compounds 9–16 were successfully synthesized by starting from
suitable chalcone and their chemical structures were confirmed by
1H NMR, 13C NMR and HRMS. The detailed interpretation of the
spectra are presented in the ‘‘Materials and methods’’ section. CA
inhibitory activities of the compounds were tested on hCA I and II
isoenzymes and the results are shown in Table 1.
When IC50 values of the compounds were considered, all
compounds [compounds(times): 9 (1.9), 10 (2.9), 11 (2.4), 12
(2.0), 13 (1.9), 14 (3.3), 15 (2.9), 16 (2.5)] had 1.9–3.3 times more
potent inhibitory potential than acetazolamide (AZA) toward hCA
I. The most effective compound toward hCA I in terms of IC50
value was 14, which has bromine substituent, while the least
effective ones were fluorine-substituted compound 13 and
nonsubstituted compound 9.
4-(3-(4-Hydroxyphenyl)-5-(thiophen-2-yl)-4,5-dihydro-1H-pyra-
zol-1-yl)benzenesulfonamide (16)
1
M.p. 249–251 ꢁC. Yield: 83%. H NMR (400 MHz, DMSO-d6,
ppm) ꢀ ¼ 9.88 (s, 1H, OH), 7.63 (d, 2H, J ¼ 8.8 Hz), 7.57 (d, 2H,
J ¼ 8.8 Hz), 7.35 (d, 1H, J ¼ 5.0 Hz), 7.13–7.11 (m, 3H), 7.01 (s,
2H, NH2), 6.92 (dd, 1H, J ¼ 5.0, 3.6 Hz), 6.82 (d, 2H, J ¼ 8.8 Hz),
5.91 (dd, 1H, J ¼ 11.4, 4.3 Hz), 3.85 (dd, 1H, J ¼ 17.6, 11.4 Hz),
3.24 (dd, 1H, J ¼ 17.6, 4.3 Hz); 13C NMR (100 MHz, DMSO-d6,
ppm) ꢀ ¼ 159.6, 151.0, 146.9, 145.4, 133.6, 128.6, 127.7, 127.5,
126.2, 126.1, 123.3, 116.3, 112.8, 58.9, 43.9; HRMS (ESI-MS):
calcd. for C19H18N3O3S2 [M + H]+ 400.0784; found 400.0767.
The inhibitory activity of the halogen-bearing compounds
toward hCA I was inversly correlated with electronegativity of the
halogen [14 with bromine (IC50 ¼299.48 nM)413 with fluorine
(IC50 ¼521.84 nM)412 with chlorine (IC50 ¼502.90 nM)] by
considering IC50 values. Any type of substituent on the phenyl
ring (except fluorine substituent) was useful modification to
increase the inhibitory potential of the compounds by decreasing
IC50 value toward hCA I.
When the methyl (10)- and methoxy (11)-substituted com-
pound’s IC50 values were compared, introduction of oxygen atom
in 11 decreased the inhibitory potential by increasing IC50 of 11.
When oxygen-bearing methoxylated compound 11 was compared
with compound 16 that is hydroxy-substituted one, 16 was more
potent inhibitor than 11. This may suggest that decrease in steric
hindrance on oxygen may be helpful to increase the inhibitory
potential toward hCA I. On the other hand, when the substituent
was nitro (15) in which two oxygen atoms are available on
nitrogen, inhibitory potential of 15 was more potent than 16. The
order of potency of the compounds toward hCA I in terms of IC50
was 15 (nitro)416 (hydroxy)411 (methoxy).
Biological activity
Carbonic anhydrase inhibition assay
Both the CA isoenzymes (hCA I and II) were purified by
Sepharose-4B-L-tyrosine-sulfanilamide affinity chromatography
in a single purification step as decscribed previously19. Thus, pH
of the solution was adjusted to 8.7 using solid Tris. Then,
supernatant was transferred to the previously prepared Sepharose-
4B-L-tyrosine-sulphanilamide affinity column20. Subsequently,
the proteins from the column were spectrophotometrically
determined at 280 nm21. For determination of the purity of the
hCA isoenzymes, sodium dodecyl sulphate-polyacrylamide gel
electrophoresis (SDS-PAGE), having 10% and 3% acrylamide as
an eluent and packing gel, respectively, with 0.1% SDS22, was
performed, through which a single band was observed for each
isoenzyme.
CA isoenzyme activities were determined following the
methods described by Verpoorte et al23 and the methods reported
previously24. Absorbance change at 348 nm from p-nitrophenyla-
cetate (NPA) to p-nitrophenolate (NP) was recorded in 3 min
intervals at the room temperature (25 ꢁC) using a spectrophotom-
eter (Shimadzu, UV-VIS Spectrophotometer, UVmini-1240,
Kyoto, Japan)25,26. Quantity of the protein was measured
It was interesting that compound 10 having methyl group on
phenyl ring, which is an electron-donating substituent, had similar
inhibitory effect (similar IC50 values) with 15, which has an
Table 1. Human CA isoenzymes (hCA I and II) inhibition value of the compounds (9–16) by the esterase method with 4-nitrophenyl acetate as
substrate.
IC50 (nM)
Ki (nM)
Compounds
hCA I
r2
hCA II
r2
hCA I
hCA II
9
520.66
338.05
412.25
502.90
521.84
299.48
337.88
401.74
985.77
0.9511
0.9964
0.9721
0.9667
0.9806
0.9903
0.9712
0.9819
0.9811
427.25
491.14
508.81
487.34
472.07
436.67
482.25
523.02
489.40
0.9726
0.9837
0.9611
0.9527
0.9704
0.9704
0.9489
0.9728
0.9972
441.99 88.26
232.16 18.17
432.85 95.90
637.70 310.3
630.58 301.1
276.32 32.91
291.74 22.74
270.17 78.36
278.76 44.28
372.48 67.37
403.33 71.60
441.02 110.8
396.91 92.80
455.80 128.4
368.52 79.11
342.07 94.07
437.60 88.43
293.43 46.41
10
11
12
13
14
15
16
AZA
Acetazolamide (AZA) was used as a standard inhibitor for all hCA isoenzymes. The results were expressed as nanomolar (nM).

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electron-attracting substituent. This may suggest that the activity
is not dependent on the electonegativity of the substituents on the
phenyl ring toward hCA I isoenzyme.
On the other hand, when IC50 value of the compounds toward
hCA II were considered, the compounds had similar IC50 to AZA.
When IC50 values of the compounds were considered, the best
inhibitor was nonsubstituted compound 9 toward hCA II. Other
substituents than hydrogen on phenyl ring decreased the inhibi-
tory activity by increasing IC50 values of the compounds. The
least effective compound was hydroxy-substituted compound 16.
Increasing steric hindrance on oxygen atom by the replacement of
hydrogen with methyl in methoxy-substituted compound 11
increased the activity toward hCA II isoenzyme, while the
introduction of nitro substituent instead of hydroxy group was a
useful modification to increase the acitivity. IC50 values of the
halogen-bearing compounds were not dependent on the electro-
negativities of the substituents.
When Ki value of the compounds toward hCA isoenzymes
were considered: Ki values were in the range of 232.16 18.17–
637.70 310.30 nM toward hCA
I
and 342.07 94.07–
455.80 128.40 nM toward hCA II, while Ki values of AZA
were 278.76 44.28 nM and 293.43 46.41 nM toward hCA I
and hCA II, respectively. According to Ki values of the
compounds toward hCA I, the most effective compound, which
has the lowest Ki value, was methyl-substituted compound 10 and
the least effective one was chlorine-substituted 12. Compound 10
and hydroxy-substituted compound 16 had more potent Ki values
than AZA, while bromine-substituted 14 has Ki value similar to
AZA toward hCA I.
When the Ki values of the compounds toward hCA II were
considered, the most effective one was fluorine-substituted
compound 13 and the least effective one was nitro-susbtituted
compound 15. All compounds were less effective than AZA
toward hCA II isoenzyme.
Compounds 10, 12, 13, 14 and 16 are reported here for the first
time, by detailed spectral analysis and bioactivities. When the
IC50 values were considered, the most effective compounds were
bromine-substituted 14, which are 3.3 times more potent than
AZA, and nonsubstituted compound 9 toward hCA I and II,
respectively. On the other hand, according to Ki values, methyl-
substituted compound 10 toward hCA I and nitro-substituted
compound 15 toward hCA II can be considered as leader
compounds for further studies.
In conclusion, we report the synthesis and CA inhibitory
activity of a new class of sulfonamides, which showed medium
potency against the cytosolic isoforms hCA I and II, presumably
due to the very bulky scaffolds present in their molecules.
However, such compounds may show interest for the inhibition of
other CA isoforms that possess a wider active site, such as hCA
IX, XII and XIV31.
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carbonic anhydrases B and C. J Biol Chem 1967;242:4221–9.
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Declaration of interest
The authors report no conflicts of interest. The authors are
responsible for the content and writing of this article. This
research work was supported by Ataturk University Research
Found, Turkey (Project No. BAP: 2013/289).
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