Synthesis, carbonic anhydrase I and II inhibition studies of the 1,3,5-trisubstituted-pyrazolines

Article abstract of DOI:10.1080/14756366.2016.1244533

4-(3-(4-Substituted-phenyl)-5-phenyl-4,5-dihydro-1H-pyrazol-1-yl) benzenesulfonamides (9–16) were successfully synthesized and their chemical structures were confirmed by ¹H NMR, ¹³C NMR, and HRMS spectra. Carbonic anhydrase I and II inhibitory effects of the compounds were investigated. K_i values of the compounds were in the range of 316.7 ± 9.6–533.1 ± 187.8 nM towards hCA I and 412.5 ± 115.4–624.6 ± 168.2 nM towards hCA II isoenzymes. While K_i values of the reference compound Acetazolamide were 278.8 ± 44.3 nM and 293.4 ± 46.4 nM towards hCA I and hCA II izoenzymes, respectively. Compound 14 with bromine and compound 13 with fluorine substituents can be considered as the leader compounds of the series because of the lowest K_i values in series to make further detailed carbonic anhydrase inhibiton studies.

Full text of DOI:10.1080/14756366.2016.1244533

Journal of Enzyme Inhibition and Medicinal Chemistry
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Synthesis, carbonic anhydrase I and II inhibition
studies of the 1,3,5-trisubstituted-pyrazolines
Halise Inci Gul, Ebru Mete, Parham Taslimi, Ilhami Gulcin & Claudiu T.
Supuran
To cite this article: Halise Inci Gul, Ebru Mete, Parham Taslimi, Ilhami Gulcin & Claudiu
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10.1080/14756366.2016.1244533
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Date: 29 October 2016, At: 14:09

JOURNAL OF ENZYME INHIBITION AND MEDICINAL CHEMISTRY, 2016
http://dx.doi.org/10.1080/14756366.2016.1244533
ORIGINAL ARTICLE
Synthesis, carbonic anhydrase I and II inhibition studies of the
1,3,5-trisubstituted-pyrazolines
Halise Inci Gula, Ebru Meteb, Parham Taslimib, Ilhami Gulcinb,c
and Claudiu T. Supurand
b
aDepartment of Pharmaceutical Chemistry, Faculty of Pharmacy, Ataturk University, Erzurum, Turkey; Department of Chemistry, Faculty of
c
Science, Ataturk University, Erzurum, Turkey; Department of Zoology, College of Science, King Saud University, Riyadh, Saudi Arabia;
d
ꢀ
Neurofarba Department, Sezione di Scienze Farmaceutiche e Nutraceutiche, Universita degli Studi di Firenze, Sesto Fiorentino, Florence, Italy
ABSTRACT
ARTICLE HISTORY
Received 14 August 2016
Revised 30 September 2016
Accepted 30 September 2016
Published online 20 October
2016
4-(3-(4-Substituted-phenyl)-5-phenyl-4,5-dihydro-1H-pyrazol-1-yl) benzenesulfonamides (9–16) were suc-
1
cessfully synthesized and their chemical structures were confirmed by H NMR, 13C NMR, and HRMS spec-
tra. Carbonic anhydrase I and II inhibitory effects of the compounds were investigated. Ki values of
the compounds were in the range of 316.7 9.6–533.1 187.8 nM towards hCA
I and 412.5
115.4–624.6 168.2 nM towards hCA II isoenzymes. While Ki values of the reference compound
Acetazolamide were 278.8 44.3 nM and 293.4 46.4 nM towards hCA I and hCA II izoenzymes, respect-
ively. Compound 14 with bromine and compound 13 with fluorine substituents can be considered as the
leader compounds of the series because of the lowest Ki values in series to make further detailed carbonic
anhydrase inhibiton studies.
KEYWORDS
Carbonic anhydrase;
enzyme; pyrazoline;
sulfonamide
Introduction
effects such as numbness and tingling in the fingers and toes,
taste alterations, blurred vision, kidney stones, and an increase in
urination14.
Carbonic anhydrases (CAs) are a ubiquitous metalloenzyme cata-
lyzing the reversible conversion of carbon dioxide to bicarbonate.
CAs are present in prokaryote and eukaryote life forms. The
enzyme is found in many tissues such as gastrointestinal tract, ner-
vous system, kidneys, lungs, skin, and eyes. CAs play key roles in a
number of physiological and pathological processes such as ions
and gas exchanges, pH regulation, photosynthesis, calcification,
and biosynthetic reactions such as gluconeogenesis, lipogenesis,
and ureagenesis1. The mammalian enzymes belonging to a-CA
family consist of 16 active members, in which several are cytosolic
(CA I–III, CA VII, and CA XIII), five are membrane-bound (CA IV, CA
IX, CA XII, CA XIV, and CA XV), two are mitochondrial (CA VA and
VB), and one (CA VI) is secreted in saliva and milk. Out of 16 differ-
ent isoforms of a-class of human-associated CAs, hCA I is found
together with hCA II in erythrocytes. hCA II is the most widely dis-
tributed isoform in the eye, kidney, central nervous system, and
inner ear, and is a drug target for clinically used diuretics, anti-
glaucoma drugs, and anticonvulsants. Targeting a particular CA is
often associated with treatment of particular diseases such as CA
II, IV, and XII are the targets for antiglaucoma agents; CA VA and
VB for antiobesity agents; CA IX and XII for antitumour agents or
On the other hand, pyrazole derivatives were registered in lit-
erature with several biological activities including antiepileptic,
antidepressant, antiinflammatory, antimicrobial, antitubercular,
anticancer, antibacterial, antioxidant, and CA inhibitory activ-
ities7,9,15–17. In addition, several 2-pyrazoline derivatives are known
with a broad range of pharmacological activities such as analgesic
and antipyretic (Phenazone/Amidopyrene/Methampyrone), antiin-
flammatory (Azolid/Tandearil), insecticidal (Indoxacarb), and urico-
suric (Anturane)18.
The most extensively made modifications on 2-pyrazolines
were diaryl/hetroaryl group substitutions at 3 and/or 5 positions.
Celecoxib and Valdecoxib, which are in clinical use, were devel-
oped as cyclooxygenase-2 (COX-2) specific inhibitors. They are also
known with their potent CA inhibitory activities19. Both com-
pounds possess a benzenesulfonamide group linked to a five-
membered substituted heterocyclic ring. The presence of the
–SO2NH2 moiety seems not to be necessary for COX-2 inhibition
but it is essential for the CA inhibition19. These two drugs have
shown interesting isoform selective CA inhibitory effects. Their
X-ray crystal structures were in a complex form with hCA II19.
Recently, our research group focused on the synthesis of the
compounds having 2-pyrazoline and sulfonamide pharmacophores
in a single molecule and investigated their several bioactivities
such as cytotoxic and/or CA inhibitory activities based on the
results of previous studies7–9,17. In the present study, it was aimed
to synthesize 4-[3–(4-substitutedphenyl)-5-phenyl-4,5-dihydro-1H-
pyrazol-1-yl] benzenesulfonamides to investigate their carbonic
anhydrase inhibitory effects on hCA I and II isoenzymes.
diagnostic tools for imaging hypoxic tumours2–5
.
The sulfonamides are an important class of the pharmaceutical
compounds with a wide spectrum of biological activities such as
anticancer6,7, CA inhibitory8,9, antibacterial10, antihypertensive11,
antiinflammatory12, and antiprotozoal13 activities among others.
On one hand, Acetazolamide (5-amino-1,3,4-thiadiazole-2-sul-
fonamide, AZA), which is used systematically to reduce intraocular
pressure by lowering the humor formation in the eye, has sulfona-
mide moiety14. Although AZA is in clinical use, it has several side
CONTACT Prof. Halise Inci Gul
Ebru Mete ebru25@atauni.edu.tr
ß 2016 Informa UK Limited, trading as Taylor & Francis Group
incigul1967@yahoo.com
Department of Pharmaceutical Chemistry, Faculty of Pharmacy, Ataturk University, Erzurum, Turkey;
Department of Chemistry, Faculty of Science, Ataturk University, Erzurum, Turkey

2
H. I. GUL ET AL.
(m, 5H), 7.25–7.22 (m, 3H), 7.06 (d, 2H, J ¼ 8.4 Hz), 7.00 (s, 2H, NH2),
5.63 (dd, 1H, J ¼ 12.1, 5.1 Hz), 3.96 (dd, 1H, J ¼ 17.8, 12.1 Hz), 3.16
(dd, 1H, J ¼ 17.8, 5.1 Hz); 13C NMR (100 MHz, DMSO-d6, ppm)
d ¼ 150.3, 146.6, 142.3, 133.7, 132.4, 130.0, 129.8, 129.4, 128.3,
127.8, 126.8, 126.4, 112.7, 63.0, 43.7; HRMS (ESI-MS): calcd. for
C21H20N3O2S [M þ H]þ 378.1271; found 378.1265.
Experimental
Materials and methods
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 (d) were reported in parts per million (ppm).
HRMS spectra of the compounds were taken by liquid chromatog-
raphy 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 (Shimadzu, Kyoto,
Japan) was used for data analysis. Melting points were determined
on Buchi 530 (Buchi Labortechnik AG, Flawil, Switzerland).
4-(5-Phenyl-3-(p-tolyl)-4,5-dihydro-1H-pyrazol-1-yl)benzenesulfo-
namide (10)
Mp 224–225 ꢀC. 3.36 g (95%). 1H NMR (400 MHz, DMSO-d6, ppm)
d ¼ 7.66 (d, 2H, J ¼ 8.1 Hz), 7.56 (d, 2H, J ¼ 9.1 Hz), 7.34–7.30 (m,
2H), 7.25–7.22 (m, 5H), 7.04 (d, 2H, J ¼ 8.8 Hz), 6.99 (s, 2H, NH2),
5.59 (dd, 1H, J ¼ 12.1, 5.1 Hz), 3.93 (dd, 1H, J ¼ 17.6, 12.1 Hz), 3.14
(dd, 1H, J ¼ 17.6, 5.1 Hz), 2.32 (s, 3H, CH3); 13C NMR (100 MHz,
DMSO-d6, ppm) d ¼ 150.4, 146.6, 142.4, 139.8, 133.5, 130.0, 129.8,
129.7, 128.3, 127.8, 126.8, 126.4, 112.6, 62.9, 43.8, 21.7; HRMS (ESI-
MS): calcd. for C22H22N3O2S [M þ H]þ 392.1427; found 392.1410.
General procedure for the synthesis of chalcones (1–8, Scheme 1)
An aqueous solution of NaOH (10%, 10 mL) was added into the
ethanol (6 mL) solution of benzaldehyde (20.0 mmol) and a suit-
able acetophenone (20.0 mmol). 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 34–82% [1 (39%), 2 (57%), 3 (82%), 4 (79%), 5 (71%), 6
(42%), 7 (34%), 8 (37%)]7,9,17,20–22.
4-(3-(4-Methoxyphenyl)-5-phenyl-4,5-dihydro-1H-pyrazol-1-
yl)benzenesulfonamide (11)
Mp 204–206 ꢀC. 2.91 g (85%). 1H NMR (400 MHz, DMSO-d6, ppm)
d ¼ 7.71 (d, 2H, J ¼ 8.8 Hz), 7.56 (d, 2H, J ¼ 8.8 Hz), 7.34–7.30 (m,
2H), 7.25–7.22 (m, 3H), 7.03 (d, 2H, J ¼ 8.8 Hz), 7.01–6.97 (m, 2H),
6.99 (s, 2H, NH2), 5.56 (dd, 1H, J ¼ 12.1, 5.1 Hz), 3.92 (dd, 1H,
J ¼ 17.6, 12.1 Hz), 3.78 (s, 3H, OCH3), 3.13 (dd, 1H, J ¼ 17.6, 5.1 Hz);
13C NMR (100 MHz, DMSO-d6, ppm) d ¼ 160.9, 150.3, 146.8, 142.4,
133.3, 129.8, 128.4, 128.2, 127.8, 126.4, 125.0, 114.9, 112.4, 62.9,
General procedure for the synthesis of pyrazolines (9–16,
Scheme 1)
55.9,
43.9;
HRMS
(ESI-MS):
calcd.
for
C22H22N3O3S
The mixture of a suitable chalcone (1.0 mmol) and 4-hydrazinoben-
zenesulfonamide hydrochloride (1.1 mmol) was dissolved in etha-
nol, and then catalytic amount of glacial acetic acid was
added7,9,17. The mixture was refluxed for 12 h. Reactions were fol-
lowed 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 crystal-
lized from methanol–ether.
[M þ H]þ 408.1376; found 408.1370.
4-(3-(4-Chlorophenyl)-5-phenyl-4,5-dihydro-1H-pyrazol-1-yl)ben-
zenesulfonamide (12)
Mp 196–198 ꢀC. 2.75 g (81%). 1H NMR (400 MHz, DMSO-d6, ppm)
d ¼ 7.77 (d, 2H, J ¼ 8.4 Hz), 7.58 (d, 2H, J ¼ 9.0 Hz), 7.48 (d, 2H,
J ¼ 8.4 Hz), 7.34–7.31 (m, 2H), 7.25–7.22 (m, 3H), 7.07 (d, 2H,
J ¼ 9.0 Hz), 7.02 (s, 2H, NH2), 5.63 (dd, 1H, J ¼ 12.1, 5.1 Hz), 3.94
(dd, 1H, J ¼ 17.8, 12.1 Hz), 3.16 (dd, 1H, J ¼ 17.8, 5.1 Hz); 13C NMR
(100 MHz, DMSO-d6, ppm) d ¼ 149.2, 146.4, 142.2, 134.4, 134.0,
131.4, 129.8, 129.4, 128.4, 128.3, 127.8, 126.4, 112.8, 63.2, 43.5;
HRMS (ESI-MS): calcd. for C21H19ClN3O2S [M þ H]þ 412.0881; found
4-(3,5-Diphenyl-4,5-dihydro-1H-pyrazol-1-yl)benzenesulfonamide
(9)
Mp 202–204 ꢀC. 2.81 g (78%). 1H NMR (400 MHz, DMSO-d6, ppm)
d ¼ 7.77 (d, 2H, J ¼ 8.1 Hz), 7.57 (d, 2H, J ¼ 8.1 Hz), 7.45–7.31 412.0873.
NH
S
2
O
O
O
O
O
N
i
ii
+
H
N
CH
3
R
R
Chalcones (1-8)
R
Pyrazolines (9-16)
(i) NaOH 10% aq, EtOH, 0-5 °C, 12 h; (ii) 4-Hydrazinobenzenesulfonamide hydrochloride, EtOH/glacial acetic acid,
reflux 12 h. 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
Scheme 1. Synthetic pathway of the benzenesulfonamides, 9–16.

JOURNAL OF ENZYME INHIBITION AND MEDICINAL CHEMISTRY
3
4-(3-(4-Fluorophenyl)-5-phenyl-4,5-dihydro-1H-pyrazol-1-yl)ben-
zenesulfonamide (13)
contained SDS (0.1%), respectively. Activities of CA I and II isoen-
zymes were determined according to the esterase method by
Verpoorte et al.26. The increase in absorbance of reaction medium
was spectrophotometrically recorded at 348 nm (UV–VIS
Spectrophotometer, Shimadzu, UVmini-1240, Kyoto, Japan). Also,
the quantity of protein was determined at 595 nm according to
Bradford method27. Bovine serum albumin was used as standard
protein. The IC50 values were obtained from activity (%) versus
compounds plots. For calculation of Ki values, three different con-
centrations were used. The Lineweaver–Burk curves were drawn
and calculations were realised28.
Mp 202–204 ꢀC. 3.03 g (87%). 1H NMR (400 MHz, DMSO-d6, ppm)
d ¼ 7.82 (dd, 2H, J ¼ 8.8, 5.5 Hz), 7.57 (d, 2H, J ¼ 9.1 Hz), 7.34–7.22
(m, 7H), 7.05 (d, 2H, J ¼ 9.1 Hz), 6.99 (s, 2H, NH2), 5.62 (dd, 1H,
J ¼ 12.1, 5.1 Hz), 3.95 (dd, 1H, J ¼ 17.9, 12.1 Hz), 3.17 (dd, 1H,
J ¼ 17.9, 5.1 Hz); 13C NMR (100 MHz, DMSO-d6, ppm) d ¼ 163.4 (d,
1J ¼ 247 Hz), 149.5, 146.6, 142.3, 133.8, 129.8, 129.1 (d, 4J ¼ 3 Hz),
129.0 (d, 3J ¼ 9 Hz), 128.3, 127.8, 126.4, 116.4 (d, 2J ¼ 21 Hz), 112.7,
63.2,
43.8;
HRMS
(ESI-MS):
calcd.
for
C21H19FN3O2S
[M þ H]þ 396.1177; found 396.1166.
Results and discussion
4-(3-(4-Bromophenyl)-5-phenyl-4,5-dihydro-1H-pyrazol-1-yl)ben-
zenesulfonamide (14)
The compounds designed were successfully synthesized. The
chemical structures of the compounds were confirmed by 1H
NMR, 13C NMR, and HRMS spectra. The CA inhibition effects of the
compounds were evaluated towards hCA I and hCA II isoenzymes.
The inhibition values are presented in Table 1. As shown in
Table 1, IC50 values were in the range of 402.9–554.8 nM towards
hCA I, while they were in the range of 458.6–620.4 nM towards
hCA II. The IC50 values of the reference compound AZA towards
hCA I and hCA II were 985.8 nM and 489.4 nM, respectively. All
compounds had lower IC50 value than AZA toward hCA I, while
the compounds 11, 14, and 16 had lower IC50 value than AZA
towards hCA II. According to IC50 values of the compounds, chlor-
ine-bearing compound 12 and bromine-bearing compound 14
were the most effective compounds towards hCA I while it was
hydroxy derivative 16 towards hCA II.
When Ki values of the compounds were considered, Ki
values of the compounds were in the range of
316.7 9.6–533.1 187.8 nM towards hCA I, while Ki values were
412.5 115.4–624.6 168.2 nM towards hCA II. The Ki values of ref-
erence compound AZA were 278.8 44.3 nM and 293.4 46.4 nM
towards hCA I and hCA II, respectively. When Ki values of the com-
pounds were considered, 12 with chlorine, 14 with bromine, and
15 with nitro substituents, which have very close Ki values, are the
leader compounds of series towards hCA I, while 14 was the
leader compound of the series towards hCA II because of the low-
est Ki values. All compounds were less effective than AZA on both
hCA I and II isoenzymes, since Ki value of the compound had
higher values than AZA’s.
Mp 190–192 ꢀC. 2.86 g (90%). 1H NMR (400 MHz, DMSO-d6, ppm)
d ¼ 7.71 (d, 2H, J ¼ 8.8 Hz), 7.62 (d, 2H, J ¼ 8.8 Hz), 7.57 (d, 2H,
J ¼ 9.0 Hz), 7.34–7.31 (m, 2H), 7.25–7.22 (m, 3H), 7.06 (d, 2H,
J ¼ 9.0 Hz), 7.01 (s, 2H, NH2), 5.63 (dd, 1H, J ¼ 12.2, 5.3 Hz), 3.94
(dd, 1H, J ¼ 17.8, 12.2 Hz), 3.16 (dd, 1H, J ¼ 17.8, 5.3 Hz); 13C NMR
(100 MHz, DMSO-d6, ppm) d ¼ 149.3, 146.4, 142.2, 134.0, 132.4,
131.7, 129.8, 128.7, 128.4, 127.8, 126.4, 123.1, 112.8, 63.2, 43.4;
HRMS (ESI-MS): calcd. for C21H19BrN3O2S [M þ H]þ 456.0376; found
456.0364.
4-(3-(4-Nitrophenyl)-5-phenyl-4,5-dihydro-1H-pyrazol-1-yl)benze-
nesulfonamide (15)
Mp 216–218 ꢀC. 2.74 g (82%). 1H NMR (400 MHz, DMSO-d6, ppm)
d ¼ 8.25 (d, 2H, J ¼ 8.6 Hz), 7.99 (d, 2H, J ¼ 8.6 Hz), 7.61 (d, 2H,
J ¼ 8.8 Hz), 7.35–7.32 (m, 2H), 7.26–7.24 (m, 3H), 7.14 (d, 2H,
J ¼ 8.8 Hz), 7.06 (s, 2H, NH2), 5.74 (dd, 1H, J ¼ 12.4, 5.3 Hz), 4.01
(dd, 1H, J ¼ 17.8, 12.4 Hz), 3.24 (dd, 1H, J ¼ 17.8, 5.3 Hz); 13C NMR
(100 MHz, DMSO-d6, ppm) d ¼ 148.3, 147.7, 145.8, 141.9, 138.8,
134.9, 129.9, 128.5, 127.8, 127.5, 126.4, 124.7, 113.4, 63.7, 43.1;
HRMS (ESI-MS): calcd. for C21H19N4O4S [M þ H]þ 423.1122; found
423.1120.
4-(3-(4-Hydroxyphenyl)-5-phenyl-4,5-dihydro-1H-pyrazol-1-
yl)benzenesulfonamide (16)
Mp 184–186 ꢀC. 0.77 g (22%). 1H NMR (400 MHz, DMSO-d6, ppm)
d ¼ 9.86 (s, 1H, OH), 7.61 (d, 2H, J ¼ 8.8 Hz), 7.54 (d, 2H, J ¼ 8.8 Hz),
7.33–7.30 (m, 2H), 7.24–7.21 (m, 3H), 6.99 (d, 2H, J ¼ 9.1 Hz), 6.97
(s, 2H, NH2), 6.81 (d, 2H, J ¼ 8.8 Hz), 5.54 (dd, 1H, J ¼ 11.7, 5.1 Hz),
3.89 (dd, 1H, J ¼ 17.6, 11.7 Hz), 3.10 (dd, 1H, J ¼ 17.6, 5.1 Hz); 13C
NMR (100 MHz, DMSO-d6, ppm) d ¼ 159.5, 150.6, 146.8, 142.5,
133.1, 129.8, 128.5, 128.2, 127.8, 126.4, 123.4, 116.2, 112.3, 62.7,
43.9; HRMS (ESI-MS): calcd. for C21H20N3O3S [M þ H]þ 394.1220;
found 394.1206.
Any substitution rather than hydrogen at the para position of
phenyl ring decreased Ki value of the substituted compound
toward hCA I by comparing with 9, which is non-substituted
derivative. This means that substitution at the para position of
phenyl ring was a useful modification to increase the effect of
compound toward hCA I. Exception was 11, which is a methoxy-
Table 1. Human CA isoenzymes (hCA I and II) inhibition value of the com-
pounds (9–16) by the esterase method with 4-nitrophenyl acetate as substrate.
Biological activity
IC50 (nM)
r2
hCA II
554.8 0.9759 586.3 0.9723 506.3 133.5 624.6 168.2
Ki (nM)
Compounds hCA I
r2
hCA I
hCA II
Carbonic anhydrase enzyme assay
9
The purification of cytosolic CA isoenzymes (CA I and II) were pre-
viously described with a simple one-step method by a Sepharose-
4B-L tyrosine-sulfanilamide affinity chromatography23. The protein
quantity in the column effluents was determined spectrophoto-
metrically at 280 nm. Sodium dodecyl sulfate-polyacrylamide gel
electrophoresis (SDS-PAGE) was applied with a Bio-Rad Mini Gel
system (Mini-PROTEAN Tetra System, Guangdong, China) after
purification of both CA isoenzymes24,25. Briefly, it was performed
in acrylamide for the running (10%) and the stacking gel (3%)
10
11
12
13
14
15
16
AZA
491.8 0.9816 620.4 0.9565 476.5 81.1 561.5 133.9
483.9 0.9743 486.3 0.9688 533.1 187.8 469.0 63.0
402.9 0.9646 559.3 0.9814 377.6 113.8 520.6 131.8
493.2 0.9709 536.0 0.9737 462.2 133.5 587.3 188.5
404.8 0.9817 470.5 0.9602 316.7 9.6
416.5 0.9815 534.3 0.9631 325.8 29.4
528.2 0.9710 458.6 0.9772 472.0 57.5
985.8 0.9811 489.4 0.9972 278.8 44.3
412.5 115.4
430.3 87.3
591.9 134.5
293.4 46.4
Acetazolamide (AZA) was used as a standard inhibitor for all hCA isoenzymes.
The results were expressed as nanomolar (nM).

4
H. I. GUL ET AL.
substituted derivative. The effect of any substituent on phenyl 11. Mujeeb Ur R, Rathore A, Siddiqui AA, et al. Synthesis and
ring to Ki value of substituted compound towards hCA II isoen-
zyme was similar to hCA I’s. It means that any type of substituent
on phenyl ring rather than hydrogen was a useful modification to
increase the compounds effect on hCA II by lowering the Ki values
without exception.
characterization of quinazoline derivatives: search for hybrid
molecule as diuretic and antihypertensive agents. J Enzyme
Inhib Med Chem 2014;29:733–43.
12. Chen Z, Wang ZC, Yan XQ, et al. Design, synthesis, biological
evaluation and molecular modeling of dihydropyrazole sul-
fonamide derivatives as potential COX-1/COX-2 inhibitors.
Bioorg Med Chem Lett 2015;25:1947–51.
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Conclusion
In conclusion, the compounds 12, 14, and 15 towards hCA I and
14 towards hCA II seem to be the leader compounds of the series
for further investigations.
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new 5-amino-1,3,4-thiadiazole-2-sulfonamide derivatives on
human carbonic anhydrase isozymes. Bioorg Med Chem
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Disclosure statement
The authors report that they have no conflicts of interest and are
responsible for the contents and writing of the paper. The authors
H. I. G. and E. M. thank to Ataturk University for the financial sup-
port. This research work was supported by Ataturk University
Research Found, Turkey (Project No: 2013/289).
15. Naim MJ, Alam O, Nawaz F, et al. Current status of pyrazole
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