Design, synthesis, molecular docking, antimicrobial, and antioxidant activities of new phenylsulfamoyl carboxylic acids of pharmacological interest

Article abstract of DOI:10.1007/s00044-019-02440-3

The research explores the facile synthesis of some new phenylsulfamoyl carboxylic acids, their molecular docking, antimicrobial, and antioxidant activities. The procedure involved the mild reaction of amino acids with benzenesulfonyl chloride in a medium

Full text of DOI:10.1007/s00044-019-02440-3

MEDICINAL
CHEMISTRY
RESEARCH
Medicinal Chemistry Research
https://doi.org/10.1007/s00044-019-02440-3
ORIGINAL RESEARCH
Design, synthesis, molecular docking, antimicrobial, and antioxidant
activities of new phenylsulfamoyl carboxylic acids of
pharmacological interest
1
Uchechukwu C. Okoro2 Sunday Okafor3
●
●
Melford C. Egbujor
Received: 25 March 2019 / Accepted: 4 September 2019
© Springer Science+Business Media, LLC, part of Springer Nature 2019
Abstracts
The research explores the facile synthesis of some new phenylsulfamoyl carboxylic acids, their molecular docking,
antimicrobial, and antioxidant activities. The procedure involved the mild reaction of amino acids with benzenesulfonyl
1
chloride in a medium of aqueous base. The compounds were characterized using FTIR, H-NMR, 13C-NMR, and an
elemental analysis. They were tested for their antimicrobial activities against Staphylococcus aureus, Escherichia coli,
Bacillus subtilis, Pseudomonas aeruginosa, Salmonella typhi, Candida albicans, and Aspergillus niger microorganisms.
The antioxidant activity of the compounds were measured in vitro by the inhibition of generated stable 2,2-diphenyl-1-
picrylhydrazyl (DPPH) free radical. The molecular docking was carried out properly and five different disease conditions
were studied, namely: trypanosomiasis, malaria, bacterial, fungal infections, and oxidative stress. From the results,
compounds 4c, 4d, 4e, and 4g possess more excellent in vitro antibacterial and antifungal activities than the standard drug
Ofloxacin used. Compound 4e displayed the most excellent antioxidant activity. Compound 4g showed significant 2D
interaction with amino acid residue of urate oxidase from Aspergillus flavus complexed with uracil. Interestingly,
compounds 4a, 4c, 4d, 4e, and 4g exhibited excellent antibacterial, antifungal, antioxidant, antitrypanosome, and antimalaria
activities comparable to the corresponding standard drugs such as Penicillin, Ketoconazole; α-Tocopherol, Melarsoprol, and
Chloroquine respectively. All the compounds were confirmed drug-like according to “Lipinski’s rule of five”. The
compounds were found to be promising antibacterial, antifungal, antioxidant, and antitrypanosome agents.
●
●
●
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Keywords Phenylsulfamoyl carboxylic acids Antibacterial activity Antifungal activity Antioxidant activity Molecular
docking
Introduction
excellent exhibition of a wide range of biological activities
such as antimicrobial, antioxidant, anti-inflammatory, and
anticancer (Madigan et al. 2012, Supuran et al. 2003). They
are said to be the most widely used antibacterial agents
employed in veterinary medicine, simply because they are
cheap and relatively efficacious in the treatment and man-
agement of common bacterial diseases (Scozzafawa et al.
2003). The sulfa drugs generally comply with the principle of
selective toxicity which takes advantage of some biological
differences between the cells of mammals and bacterial
(Henry 1943). Every bacterium cell needs folic acid for
growth and replication. In humans, folic acid being a vitamin
can be supplied by food and are diffused or transported into
mammalian cells. On the contrary, folic acid does not
permeate bacterial cell walls and therefore bacterial depend on
synthesize of folic acid from p-aminobenzoic acid (Lehne
1994). Indeed, sulfonyl and amide groups when combined
Compounds containing sulfonyl and amide groups are widely
recognized as pharmaceutical compounds because of their
* Melford C. Egbujor
egbujormc@gmail.com
* Sunday Okafor
sunday.okafor@unn.edu.ng
1
Department of Industrial Chemistry, Renaissance University,
Ugbawka, Enugu, Nigeria
2
Department of Pure and Industrial Chemistry, Synthetic Organic
Chemistry Division, University of Nigeria, Nsukka, Nigeria
3
Department of Pharmaceutical and Medicinal Chemistry,
University of Nigeria, Nsukka, Nigeria

Medicinal Chemistry Research
together play essential role in medicine, chemical, and phar-
maceutical industries. However, there is a reduction in wide
use of these drugs, probably because bacterial strains are
developing resistance to the old existing sulfonamides, also
toxicity, bioavailability, and drug potency of these drugs have
been of great concern (Levy 2002; Karch 2011). This can be
attributed to the fact that many researchers have limited their
research to the conventional method of preparing sulfona-
mides using ordinary amines, and only a few detailed anti-
microbial, antioxidant, and molecular docking studies have
been reported (Greenfield and Grisanu 2008; Bonk et al.
2007). Amino acids are human friendly as opposed to amines
(Lubec et al. 1991). α-Amino acids have been found better
coupling partners in drug synthesis than ordinary amines
because of the issues of odor, solubility, toxicity, and bioa-
vailability (Bandelin and Walter 2006; Remko and Vonder-
Lieth 2004; Crystal and Ron 2010). Moreover, α-amino acids
are naturally occurring and the most important group of
amino acids in the biological world (Young 1994). The use of
α-amino acids in the research work is targeted at achieving
improved drug potency with minimal or no toxicity. There-
fore, an urgent need to intensify research on the synthesis of
new phenylsulponamoyl carboxylic acids using biologically
active amino acids and subjecting them to detailed anti-
microbial, antioxidant, and molecular docking studies in order
to maximize their usefulness has necessitated the
research work.
Microbiology, University of Nigeria, Nsukka. The anti-
oxidant studies were carried out at the Biochemistry
Department, University of Nigeria, Nsukka
General procedure for the synthesis of
phenylsulfamoyl carboxylic acids
Using a 100 ml beaker, amino acid (25 mmol) was dis-
solved in water (30 ml) and sodium carbonate (5.58 g,
52.50 mmol) was added with continuous stirring to ensure
complete dissolution of the solutes. The clear solution was
cooled to 0 °C followed by the addition of benzenesulfonyl
chloride (5.72 g, 30 mmol) in three portions for 1 h interval.
Then the slurry was stirred for 5 h at room temperature and
the reaction mixture was acidified to pH 2 with 2 M
hydrochloric acid (HCl) to facilitate crystallization. It was
allowed to settle down for at least 12 h and the product was
separated through suction filtration. The filtered crude pro-
duct was washed with tartaric acid (pH2.2) and dried to
obtain substituted benzenesulfonamides alkanamides (4a–
4g) in good to excellent yields (61–98.5%) shown in
Scheme 1.
2-[(phenylsulfonyl)amino]propanoic acid (4a)
The amino acid used was analine, yield 3.83 g (82.6%), mp
117–118 °C, IR(KBr) cm−1: 3328, 3268 (N–H), 3066 (C–H
aromatic), 2991 (CH aliphatic), 1722 (C=O of COOH),
1154, 1087 (SO2 two bands), 725 (Ar–H). 1H-NMR
(DMSO-d6) δ: 10.63 (s, IH, OH of COOH), 8.16–8.15 (d,
J = 8.4 Hz, 1H, NH–CH), 7.84–7.81 (d, J = 8.53 Hz, 2H,
Ar–H), 7.67–7.57 (m, 3H, Ar–H), 3.78–3.73 (dd, J1 =
7.30 Hz, J2 = 8.37 Hz, 1H, NH–CH–CH3), 1.14–1.12 (d, J
= 7.20 Hz, 3H, CH3–CH). 13CNMR (CD3N, 400 MHZ) δ:
170.282, (C=O), 149.9 (2CH, 2C-5), 141.1 (2CH, 2C-3),
131.6 (CH, C-4), 129.6 (C, C-2), 64.3 (CH3, C-7), 45.3 (C,
CH, C-6). Anal. calcd. for C9H10NO4S (228.0): C, 47.35, H,
4.38, N, 6.14. Found: C, 47.34, H, 4.40, N, 6.20.
Materials and methods
Chemistry
Reagents were purchased from Sigma-Aldrich. Melting
points of the compounds synthesized were determined using
electrothermal melting point apparatus and are uncorrected.
Infrared spectra data were recorded on 8400s Fourier
Transform Infrared (FTIR) (ABU, Zaria, Kaduna State,
Nigeria). Nuclear Magnetic Resonance (1H-NMR and 13C-
NMR) were run on 400 MHz using NMR spectro-
photometer at Sandeep Verma Laboratory, Department of
Chemistry, Indian Institute of Technology, Kanpur. Che-
mical shifts were reported in δ scale (neat). The anti-
microbial studies were carried out at the Department of
1-(phenylsulfonyl)pyrrolidine-2-carboxylic acid (4b)
The amino acid used was proline, yield 3.13 g (95.8%), mp
74–76 °C. IR(KBr) cm−1: 3065 (CH aromatic), 2981 (O–H
of COOH), 1722 (C=O of COOH), 1334, 1155 (S=O two
O
O
Scheme 1 Synthesis of
substituted benzenesulfamoyl
carboxylic acids
O
O
O
H O
Na2CO3,
S
2
R
S
NH
Cl
25OC, 4hr, pH=2
OH
R
+
NH3
amino acid
O
2
3
OH
4a-4g
benzenesulphonyl chloride
substituted
benzenesulphonamides

Medicinal Chemistry Research
1
bands), 689 (Ar–H). H-NMR (CDCl3) δ: 10.09–9.98 (s,
COOH), 2967 (CH aromatic), 1725 (C=O of COOH), 1449
(C=C aromatic), 1319, 1162 (S=O two bands), 760
(Ar–H). HNMR (DMSO, 400 MHz) δ: 7.793–7.771 (m,
2H, ArH), 7.688–7.519 (m, 2H, ArH), 4.742 (s, IH, OH),
3.553–3.518 (m, IH, COOH), 2.482–2.475 (m, 3H,
CH3–C=O), 1.878 (s, IH, CH–OH). 13CNMR (CD3OD/
DMSO, 400 MHz) δ: 170.2 (C=O), 143. 4 (2CH, 2C-5),
130.8 (2CH, 2C-3) 125.9 (CH, C-4), 124.2 (C, C-2). Anal.
calcd. for C9H10NO5S (244.10): C, 44.24, H, 4.10, N, 5.74.
Found: C, 44.19, H, 4.10, N, 5.79.
1H, OH of COOH), 7.82–7.79 (d, J = 8.77 Hz, 2H,Ar–H),
7.58–7.49 (m, 3H, Ar–H), 4.79–4.78 (d, J = 5 Hz, 1H,
CH–COOH), 3.78–3.75 (d, J = 10 Hz, 1H, CH of CH2–N),
3.25–3.19 (d, J1 = 2.8 Hz, J2 = 10 Hz, 1H, CH of CH2–N),
2.19–2.15 (m, IH, CH), 1.73–1.68 (m, 3H, CH2, and CH),
1.49–1.44 (m, 1H, CH), 1.35–1.26 (m, 1H,CH). 13C–NMR
(DMSO-d6) δ: 170.5 (C=O), 143.8 (2CH, 2C-5), 134.9
(2CH, 2C-3), 129.7 (CH, C-4), 127.4 (C, C-2), 67.3 (CH2,
C-7), 60.7 (CH2, C-8), 48.8 (CH2, C-9), 30.6 (CH, C-6).
Anal. calcd. for C11H12NO4S (254.12): C, 51.94, H, 4.72,
N, 5.51. Found: C, 51.89, H, 4.40, N, 5.46.
I
3-hydroxy-2-[(phenylsulfonyl)amino]butanoic acid (4f)
2-[(phenylsulfonyl)amino]-3-sulfanylpropanoic acid (4c)
The amino acid used was threonine, yield 2.99 g (88.9%),
mp 143–145 °C. IR(KBr) cm−1: 3533 (OH free), 3287
(N–H), 3063 (C–H aromatic), 2945 (O–H of COOH), 1714
(C=O of COOH), 1326, 1162 (S=O two bands), 685
(Ar–H). 1H-NMR (DMSO-d6) δ: 10.55 (s, 1H, OH of
COOH), 7.82–7.81 (d, J = 8.7 Hz, 2H, Ar–H), 7.69–7.66
(d, J = 9.3 Hz, 1H, NH–CH), 7.61–7.53 (m, 3H, Ar–H),
The amino acid used was cysteine, yields 2.85 g (84.3%),
mp 175–178 °C. IR(KBr) cm−1 : 3291 (N–H), 3168 (OH of
COOH), 3063 (C–H aromatic), 2571 (S–H), 1736 (C=O of
COOH), 1587 (C=C aromatic), 1326, 1151 (S=O two
I
bands), 685 (Ar–H). H-NMR (DMSO-d6) δ: 10.96 (s, 1H,
OH of COOH), 8.37–8.34 (d, J = 8.41 Hz, 1H, NH–CH),
7.79–7.77 (d, J = 8.65 Hz, 2H, Ar–H), 7.65–7.54 (m, 3H,
Ar–H), 3.94–3.89 (dd, J1 = 8.41 Hz, J2 = 20.01 Hz, 1H,
NH–CH–CH), 2.93–2.88 (dd, J1 = 5.61 Hz, J2 = 20.10 Hz,
1H, CH of CH2–S), 2.62–2.56 (dd, J1 = 8.23 Hz, J2 =
20.10 Hz, 1H, CH of CH2–SH). 171.3 (C=O), 143.6 (2CH,
2C-5), 134.3 (2CH, 2C-3), 122.4 (CH, C-4), 120.5(C, C-2),
77.402, 77.1 (CH, C-6), 76.8 (CH2, C-7). Anal. calcd. for
C9H10NO4S2 (260.10): C, 41.52, H, 3.84, N, 5.38. Found:
C, 41.47, H, 3.80, N, 5.42.
3.99–3.98
(dd,
J1 = 3.61 Hz,
J2 = 6.41 Hz,
1H,
CH–CH–CH3), 3.69–3.67 (dd, J1 = 3.60 Hz, J2 = 9.20 Hz,
1H, NH–CH–CH), 2.08 (s, 1H, OH), 1.02–1.01 (d, J =
6.40 Hz, 3H, CH3–CH). 13CNMR (DMSO, 400 MHz) δ:
171.4 (C=O), 141.9 (2CH, 2C-5), 133.8 (2CH, 2C-3),
129.4 (CH, C-4), 126.9 (C, C-2), 67.6 (CH, C-6). 61.6
(CH2, C-7). for C10H12NO5S (258.12): C, 46.49, H, 4.65, N,
5.42. Found: C, 46.52, H, 4.69, N, 5.38.
4-methyl-2-[(phenylsulfonyl)amino]pentanoic acid (4g)
4-[(methylsulfanyl)-2-(phenylsulfonyl)amino]butanoic acid
(4d)
The amino acid used is leucine, yield 2.82 g (88.1%), mp.
113–115 °C. IR(KBr) cm−1: 3242 (N–H), 2959 (OH of
COOH), 2922 (C–H aromatic), 1707 (C=O of COOH),
1312, 1166 (S=O two bands), 689 (Ar–H). 1H-NMR,
(DMSO-d6) δ: 8.07 (d, J = 8.62 Hz, 1H), 7.66 (d, J =
8.16 Hz, 1H), 7.51 (dd, J1 = 5.67 Hz, J2 = 7.45 Hz, 1H),
7.36 (d, J = 8.08 Hz, 1H), 7.16 (d, J = 7.97 Hz, 1H), 3.64
(d, J = 8.30 Hz, 1H), 2.31 (s, 3H), 1.57 (dd, J1 = 6.56 Hz,
J2 = 12.94 Hz, 2H), 1.35 (m, 1H), 0.81 (d, J = 6.61 Hz,
3H), 0.68 (d, J = 6.50 Hz, 3H). 13CNMR (DMSO,
400 MHz) δ: 171.2 (C=O), 137.1 (2CH, 2C-5), 133.8
(2CH, 2C-3), 133.6 (CH, C-4) 132.5 (C, C-2), 40.1 (CH, C-
6), 39.8 (CH2, C-7). Anal. calcd. for C12H18NO4S (263.10):
C, 54.73, H, 6.84, N, 5.32. Found: C, 54. 69, H, 6.80, N,
5.28. (Scheme 2).
The amino acid used was methionine, yield 2.90 g (82.1%),
mp 127–129 °C, IR(KBr) cm−1: 3324 (N–H), 3205 (OH of
COOH), 3063 (CH aromatic), 1595 (C=C aromatic), 1312,
1
1162 (S=O two bands), 756 (Ar–H). H-NMR (DMSO-d6)
δ: 10.74 (s, 1H, OH of COOH), 8.23–8.21 (d, J = 8.7 Hz,
1H, NH–CH), 7.78–7.76 (d, J = 8.54 Hz, 2H, Ar–H),
7.65–7.56 (m, 3H, Ar–H), 3.88–3.85 (dd, J1 = 4.10 Hz, J2
= 8.81 Hz, 1H, NH–CH–CH3), 2.38–2.27 (m, 2H, CH2S),
1.92 (s, 3H, CH3), 1.84–1.75 (m, 2H, CH2–CH2–S).
13CNMR (DMSO, 400 MHz) δ:171.3 (C=O), 146.5 (2CH,
2C-5), 137.4 (2CH, 2C-3), 133.8 (CH, C-4), 132.7 (C, C-2),
49.7 (CH, C-6), 48.4 (CH2, C-7), 47.2 (CH2, C-8), 47.0
(CH3, C-9). Anal. calcd. for C11H14NO4S2 (288.14): C,
45.81, H, 4.86, N, 4.86. Found: C, 45.77, H, 4.40, N, 5.79.
Antimicrobial studies procedure
3-hydroxy-2-[(phenylsulfonyl)amino]propanoic acid (4e)
The test microorganisms used
The amino acid used was serine, yield 2.00 g (70.1%), mp
The test microorganisms used (Staphylococcus aureus,
Escherichia coli, Bacillus subtilis, Pseudomonas
140–142 °C, IR(KBr) cm−1: 3421 (N–H), 3287 (O–H of

Medicinal Chemistry Research
O
O
S
NH
CH3
CH3
O
O
O
S
4g
NH
OH
O
4a
CH3
O
O
Leuci
O
O
n
e
OH
S
S
NH
N
CH3
O
O
T
h
4f
reoni
ne
e
SO2 Cl
lin
4b
o
r
P
OH
OH
OH
O
O
S
e
n
i
r
Se
NH
Cystei
O
n
e
O
O
O
4e
OH
O
S
S
N H
OH
N H
CH3
O
SH
O
S
4d
4c
OH
OH
Scheme 2 Synthetic pathway for new phenylsulfamoyl carboxylic acids
aeruginosa, Salmonella typhi, Candida albicans, and
Aspergillus niger) were clinical isolates obtained from the
department of pharmaceutical microbiology and bio-
technology laboratory, University of Nigeria, Nsukka.
were incubated in inverted position at 37 °C for 24 h, and at
25 °C for 48 h. After the due period of incubation, the plates
were observed for sensitivity and resistivity of the organ-
isms to the agents, and the observation was recorded. The
plates were further incubated for another 24 h at 37 °C, and
48 h at 25 °C to determine whether the activity was bac-
teriostatic or bactericidal. The observation was also
recorded.
Standardization of the test organism suspension
The organisms were standardized using 0.5 McFarland
turbid equivalents.
Antioxidant studies procedure
Control test (standard)
Antioxidant activity by DPPH method
The standard antibiotic used was ofloxacin, ciprofloxacin,
and fluconazole.
The antioxidant behavior of the synthesized compounds
were measured in vitro by the inhibition of generated stable
2,2-diphenyl-1-picrylhydrazyl (DPPH) free radical. The
DPPH solution was prepared by dissolving 1.9 mg of DPPH
in 100 ml of methanol. Three different concentrations (50,
100, and 200 µg/ml) of the DPPH soluion were prepared.
Two milligrams of each of the synthesized compounds was
weighed out and dissolved in 10 ml of appropriate solvent.
The stock solution (200 µg/ml) was diluted further to get
100 and 50 µg/ml for each of the samples. The standard
solution of ascorbic acid was prepared in similar manner.
One milliliter of DPPH solution was added to 2 ml solution
of the samples and ascorbic acid. The reaction mixture was
vortexed thoroughly and left in the dark at room tempera-
ture for 30 min. The absorbance of the mixture was
Experimental
A total of 4.0 ml of sample suspension of stock concentra-
tion 50 mg/ml was transferred to the sterile Petri dish, a
16.0 ml volume of double strength sterile molten agar was
transferred to the same plate to mix uniformly thus, 1 mg/ml
concentration was obtained. The other concentrations 0.9,
0.8, 0.7, 0.6, 0.5, 0.4, 0.3, 0.2, and 0.1 mg/ml, were
obtained using the same C1V1=C2V2 formula. The molten
agar plates with different concentrations of the sample were
allowed to gel. The plates were divided into seven equal
parts with permanent marker. The test microorganisms were
streaked on the segments, and labeled. The culture plates

Medicinal Chemistry Research
measured (in triplicate) spectrophotometrically at 517 nm
against the corresponding blank solution. The percentage
scavenging DPPH radical inhibitions were calculated by
using the following formula:
Abscontrol À Abssample
DPPH radical scavenging activity ð%Þ ¼
 100
ð1Þ
Abscontrol
where, Abscontrol was the absorbance of DPPH radical and n-
hexane/methanol, Abssample was the absorbance of DPPH
radical and sample/standard.
In silico methodology
Physicochemical properties
Fig. 1 The 2D representation of the interactions of compound 4g with
the amino acid residues of 1WS3
The physicochemical properties of the synthesized com-
pounds were generated in silico. They include Molecular
weight (MW), number of hydrogen bond acceptor (HBA),
number of hydrogen bond donor (HBD), number of rota-
table bond (NRB), octanol/water partition coefficient logP
(o/w), aqueous solubility (SlogP) and topological polar
surface area (TPSA). These parameters were computed by
descriptors calculator in Swiss dock and PreADME online
servers. The drug-likeness was evaluated using Lipinski’s
rule of five.
complexed with uracil (PDB code: 1WS3), and antioxidant:
human peroxiredoxin 5 (PDB code: 1HD2). The 3-
dimensional structures of these drug targets were down-
loaded from the Protein Data Bank (PDB), (http://www.
pdb.org) database. The prepared compounds were then
subjected to interact with each of the receptors through
molecular docking using PyRx. The protocol facilitates
flexible compound docking for various compound con-
formers within the rigid receptor. Best conformation for
each compound was chosen and the interaction was visua-
lized in Discovery studio. The docking protocol was vali-
dated as shown in Fig. 1 with rmsd = 2.4 Å (Ekennia
Anthony et al. 2018).
Toxicity prediction
ProTox-II webserver was used to predict the toxicity of the
synthesized compounds (Banerjee et al. 2018). The fol-
lowing toxicity endpoints were computed:
Predicted median lethal dose (LD50);
Organ toxicity (hepatotoxicity);
Toxicity endpoints including carcinogenicity, immuno-
toxicity, mutagenicity, and cytotoxicity;
Results and discussion
Nuclear receptor signaling pathways including androgen
receptor (AR) and estrogen receptor alpha (ER).
The synthesis of para-toluene sulfonamides was achieved
by the reaction of p-toluene sulfonyl chloride with amino
acids in a basic medium at temperature below 0 °C. Then
the reaction mixture was stirred for 4 h at room temperature
to generate para-toluene sulfonamides (4a–4g).
Molecular docking
Five different disease conditions were studied, namely:
trypanosomiasis, malaria, bacterial and fungal infections,
and oxidative stress. A drug target was chosen for each of
the disease conditions for molecular docking studies. The
drug targets for antitrypanosomiasis: T. brucei farnesyl
diphosphate synthase complexed with minodronate (PDB
code: 2EWG); antimalarial: plasmepsin II, a hemoglobin-
degrading enzyme from Plasmodium falciparum, in com-
plex with pepstatin A (PDB code: 1SME); antibacterial: E.
coli DNA gyrase in complex with 1-ethyl-3-[8-methyl-5-(2-
methyl-pyridin-4-yl)-isoquinolin-3yl]urea (PDB code:
5MMN); antifungal: urate oxidase from Aspergillus flavus
Reaction mechanism
When in an aqeous medium, an amino acid forms a zwit-
terions by the transfer of an +H ion from one end of the
molecule to the other (Price et al. 1997). The reaction
mechanism is represented in (Scheme 3) below.
Antimicrobial studies results
The antimicrobial Studies (Table 1) revealed that com-
pounds 4a, 4b, 4c, 4d, 4e, 4f, and 4g have outstanding

Medicinal Chemistry Research
Scheme 3 Reaction mechanism
for new phenylsulphonamoyl
carboxylic acids
O
-
O
S
Cl
S
Cl
O
O
H3 N +
:
NH3
step 2: nucleophilic attack of the
amino group on the electophilic
sulphur atom breaking the S=O bond
step 3: transfer of the H on the amino N atom
to the negatively charged oxygen
R
R
H3 N + CHCOO-
H2 NCHCOOH
H
O
step 1: formation of zwitterion
S
Cl
O
H2 N
step 4: HCl formed is eliminated from the
intermediate to obtain benzenenesulphonamide
-HCl
O
S
H2 N
O
benzenesulphonamide
Table 1 Antimicrobial activities
of compounds (4a–4g)
Minimum inhibitory concentration (MIC)(mg/ml)
Compounds
E. coli
S. typhi
S. aureus
B. sub
Ps. aerug
C. albicans
A. niger
4a
ND
0.5
0.6
0.9
1.0
0.9
0.9
0.5
2.0
0.9
0.7
0.7
0.8
0.7
0.9
0.9
1.0
1.5
1.0
0.9
ND
ND
0.8
0.8
0.8
1.0
2.0
0.5
0.7
0.9
0.8
0.9
0.6
0.8
2.0
2.0
ND
0.7
ND
ND
ND
0.9
ND
2.0
2.0
0.7
ND
1.0
1.0
0.7
0.9
ND
ND
ND
0.9
0.9
ND
ND
ND
0.8
ND
ND
ND
4b
4c
4d
4e
4f
4g
Ofloxacin
Ciprofloxacin
ND not determined
antimicrobial (antibacterial and antifungal) activities when
compared with commercial standard drug. It was also
observed that compounds 4c, 4d, 4e, and 4g possess more
excellent antibacterial and antifungal activities than the
commercial standard drugs Ofloxacin used. This suggest
that these new phenylsulfamoyl carboxylic acids can serve
as better antibacterial and antifungal agents than standard
commercial drugs and therefore should be considered
accordingly.
Antioxidant studies results
The in vitro antioxidant studies (Table 2) showed that some
of the tested compounds had antioxidant activities. Com-
pounds 4c, 4d, and 4e, showed impressive antioxidant
activities. Only compound 4e (96.70% inhibition at 200 µg/
ml) had almost the same antioxidant activity with the
standard ascorbic acid (96.83% inhibition at 200 µg/ml).
This suggests that compounds 4e was the most potent

Medicinal Chemistry Research
Table 2 Antioxidant activities
results
200 µg/ml
100 µg/ml
50 µg/ml
Sample
% inhibition
Std
% inhibition
Std
% inhibition
Std
Ascorbic acid
96.83
94.26
93.53
96.70
87.30
0.001
0.012
0.001
0.000
0.001
97.68
82.30
82.78
73.50
86.32
0.001
0.002
0.000
0.001
0.002
97.31
37.91
72.83
71.79
79.55
0.001
0.011
0.001
0.000
0.001
4c
4d
4e
4f
Table 3 Physicochemical properties
cells. The compounds did not inhibit any of the Cytochrome
P450 enzymes (CYP1A2, CYP2C19, CYP2C9, CYP2D6,
and CYP3A4). The log of skin permeability coefficient (log
Kp) obtained for the compounds ranged from −7.92 to
−5.96 cm/s.
Mol HBA HBD NRB logP(o/w) SlogP TPSA MW
LV
4a
4b
4c
4d
4e
4f
4
4
4
4
5
5
5
3
2
3
3
4
4
2
4
3
5
7
5
5
7
0.97
0.81
0.44 83.47 229.26
0.92 74.68 255.29
0.35 122.27 261.32
1.17 83.47 289.38
−0.59 103.70 245.25
−0.20 103.70 259.28
1.72 91.75 313.37
0
0
0
0
0
0
0
1.08
1.62
Toxicity studies
−0.07
0.40
The predicted toxicity of all the compounds is listed in
Table 5. These compounds are inactive for hepatotoxicity,
carcinogenicity, immunotoxicity, mutagenicity, and cyto-
toxicity. They are also inactive for nuclear receptor sig-
naling AR and ER. The predicted LD50 for compounds
ranged from 1200 to 2070 mg/kg.
4g
2.33
MW molecular weight, HBD hydrogen bond donor, HBA hydrogen
bond acceptor, logP(o/w) octanol/water partition coefficient, SlogP
aqueous solubility, TPSA topological polar surface area, LV Lipinski
violation
antioxidant agent and therefore further derivatization of the
potent compound 4e is necessary to improve the drug-
likeness.
Molecular docking results
The calculated free binding energy after molecular docking
is given in Table 6. Our compounds showed strong binding
affinities with all the receptors used for this study. Among
all the compounds tested on 2EWG, 4 and 24 gave the
lowest binding energy (highest binding affinity) of 15.01
and 15.19 kcal/mol, respectively. However, the standard
drug for the treatment of trypanosomiasis (melarsoprol)
showed highest binding affinity with 2EWG (−19.36 kcal/
mol). Likewise, compound 43 showed the highest binding
affinity (−13.49 kcal/mol) with the Plasmodium falciparum
pepstatin A receptor (1SME) when compared with the
standard drug (chloroquine) for malaria treatment, whose
binding affinity is −10.08 kcal/mol. For the DNA gyrase
receptor, compound 56 had more binding affinity with it
(−11.93 kcal/mol) than with penicillin (−10.89 kcal/mol).
The recptor for antifungal study, 1WS3 has highest binding
affinity with compound 14 (−11.88 kcal/mol), which was
better than that of ketoconazole (−10.38 kcal/mol). Finally,
compounds 4 and 56 outperformed α-tocopherol in their
binding affinities with 1HD2. The binding affinities of 4
and 56 were −14.90 and −14.68 kcal/mol when compared
with the standard drug (−9.34 kcal/mol).
Physicochemical properties results
The physicochemical properties to evaluate the drug-
likeness of the synthesized compounds are shown in
Table 3. Lipinski’s rule of five (Ro5) is very important in
assessing the drug-likeness of a molecule. According to this
rule, a molecule must have molecular weight value of ≤500,
hydrogen bond donor ≤5, hydrogen bond acceptor ≤10, and
partition coefficient (Log P) value ≤5. Violation of more
than one parameter may pose a challenge to the bioavail-
ability of the molecule in case of oral formulation. From the
results in Table 1, the synthesized compounds are in
agreement with (Ro5).
Pharmacokinetics studies
The Pharmacokinetics profiles of the synthesized com-
pounds are shown in Table 4. All the compounds showed a
high gastrointestinal absorption. None of the compounds is
a blood–brain barrier permeantm and therefore will not have
any effect on the central nervous system (CNS). It was also
observed that none of the compounds bound to the per-
meability glycoprotein (Pgp), an important protein of the
cell membrane that pumps many foreign substances out of
To gain further insight into the molecular interactions of
these compounds with the receptors, we examined their
binding poses in the binding cavities of the drug receptors.
These have been shown in Figs. 2 and 3.

Medicinal Chemistry Research
Table 4 Pharmacokinetics profiles of the compounds
Comp GI absorption BBB
permeant
Pgp
substrate
CYP1A2
inhibitor
CYP2C19
inhibitor
CYP2C9
inhibitor
CYP2D6
inhibitor
CYP3A4
inhibitor
log
Kp (cm/s)
4a
4b
4c
4d
4e
4f
High
High
High
High
High
High
High
No
No
No
No
No
No
No
No
No
No
No
No
No
No
No
No
No
No
No
No
No
No
No
No
No
No
No
No
No
No
No
No
No
No
No
No
No
No
No
No
No
No
No
−6.64
−7.01
−7.32
−6.55
−7.92
−7.69
−5.96
No
No
No
No
No
No
4g
Table 5 Toxicity report
Comp LD50 Hepatotoxicity Carcinogenicity Immunotoxicity Mutagenicity Cytotoxicity Androgen
Estrogen receptor
alpha (ER)
(mg/kg) receptor (AR)
4a
4b
4c
4d
4e
4f
1200
Inactive
Inactive
Inactive
Inactive
Inactive
Inactive
Inactive
Inactive
Inactive
Inactive
Inactive
Inactive
Inactive
Inactive
Inactive
Inactive
Inactive
Inactive
Inactive
Inactive
Inactive
Inactive
Inactive
Inactive
Inactive
Inactive
Inactive
Inactive
Inactive
Inactive
Inactive
Inactive
Inactive
Inactive
Inactive
Inactive
Inactive
Inactive
Inactive
Inactive
Inactive
Inactive
Inactive
1200
1200
2070
1200
2070
2000
Inactive
Inactive
Inactive
Inactive
Inactive
Inactive
4g
Table 6 In silico
Antitrypanosomiasis
Antimalaria
1SME
Antibacterial
5MMN
Antifungal
Antioxidant
1HD2
antitrypanosomal, antimalerial,
antibacterial, antifungal, and
antioxidant activities
Compound
2EWG
1WS3
4a
−13.40
−12.87
−14.34
−14.21
−14.48
−13.85
−13.25
−14.36
−13.25
−11.66
−11.40
−11.46
−11.80
−12.48
−11.15
−10.08
−10.36
−10.17
−10.84
−10.43
−10.68
−10.58
−11.03
−10.89
−10.81
−11.05
−10.66
−11.65
−10.79
−10.46
−11.88
−10.85
−12.73
−11.83
−13.42
−12.79
−13.49
−12.18
−12.41
−14.82
4b
4c
4d
4e
4f
4g
Standard drug
Standard drugs for 2EWG—Melarsoprol; 1SME—Chloroquine; 5MMN—Penicillin; 1WS3—Ketoconazole;
1HD2—α-Tocopherol
ADMET parameters
In silico antioxidant activities
In silico antibacterial activities
The in silico antioxidant studies (Table 6) revealed that only
compounds 4c and 4e (−13.42 and 13.49 kcal/mol) had
The in silico antifugal studies (Table 6) revealed that
compounds 4b, 4d, and 4g with binding energies −11.05,
−11.65, and −11.88 kcal/mol, respectively possess more
excellent antifungal activities that the commercial standard
drug with binding energy −10.85 kcal/mole. This suggest
that these new phenylsulfamoyl carboxylic acids can serve
as better antifungal agents that standard commercial drugs
and therefore should be considered accordingly.
comparable binding energy with α-tocopherol (−14.82 kcal/
mol). Compounds 4c and 4e are the most promising but not
as effective as the standard ascorbic acid.
In silico antitrypanosomal activities
The in silico antitrypanosomal studies (Table 6) revealed
that compounds 4c, 4d, and 4e, having binding energy

Medicinal Chemistry Research
In silico antimalarial activities
The in silico Antimalarial Studies (Table 6) revealed that all
the compounds 4a–4g with binding energy (−13.25, −11.66,
−11.40, −11.46, −11.80, −12.48, −11.15 kcal/mol) against
Plasmodium Falciparuim as excellent inhibitor of dihy-
drofolate reductase. These new phenylsulfamoyl carboxylic
acids when compared with the most potent standard anti-
malaria agent Chloroquine (−10.08 kcal/mol) showed better
binding energies with compound 4f, being the most excellent
and therefore can be used as antimalarial agents.
Figures 2 and 3 revealed how compound 4g occupied the
binding sites of 1WS3 and the necessary interactions
between the 14 and the receptor. The H of the O-19 of 14
interacted with the π electrons from the 6-ring PHE 159
through H–π interactions. The intermolecular distance and
energy of interaction were given to be 3.05 Å and
−0.2 kcal/mol, respectively. Also, O-19 of 4 interacted with
NH1 ARG 176 through H–acceptor interaction. Two other
H-bond were observed. These were between O-21 and ND2
of ASN 254, and O-21 and CE1 of HIS 256.
Fig. 2 Validation of the docking protocol
Conclusion
In conclusion, a facile synthesis of phenylsulfamoyl car-
boxylic acids (4a–4g) was successful. The assigned struc-
tures were in agreement with the spectral data. They were
also subjected to antimicrobial, antioxidant and in silico
studies and were found to possess interesting biological and
pharmacological activities. The findings demonstrated that
compounds 4d, 4e, and 4g possess more excellent in vitro
antibacterial and antifungal activities and therefore potent
antibacterial and antifungal agents. Compound 4e displayed
the most excellent antioxidant activity is therefore promis-
ing antioxidant agent. The molecular docking revealed that
compound 4g showed significant 2D interaction with amino
acid residue of urate oxidase from Aspergillus flavus com-
plexed with uracil and compounds 4a, 4c, 4d, 4e, and 4g
exhibited excellent antibacterial, antifungal, antioxidant,
antitrypanosome, and antimalaria activities similar to the
corresponding standard drugs. The synthesized compounds
are potent antibacterial, antifungal, antioxidant, anti-
trypanosome, and antimalaria agents.
Fig. 3 The binding pose of compound 4g in the binding cavity
of 1WS3
Acknowledgements We acknowledge the Chemistry Department of
Renaissance University Enugu and University of Nigeria Nsukka,
Nigeria for providing the labs and instruments.
−14.34, −14.21, and −14.48 kcal/mol, respectively are
comparable to the standard drug Melarsoprol (−14.36 kcal/
mol). It implies that the new phenylsulfamoyl carboxylic
acids can serve as inhibitors of Trypanosome Brucei and
therefore should be considered in the treatment of trypa-
nosomiasis (sleeping sickness).
Compliance with ethical standards
Conflict of interest The authors declare that they have no conflict of
interest.

Medicinal Chemistry Research
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jurisdictional claims in published maps and institutional affiliations.
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