Synthesis of sulfanilamide derivatives and investigation of in vitro inhibitory activities and antimicrobial and physical properties

Article abstract of DOI:10.1016/j.bioorg.2011.02.004

Novel sulfanilamide derivatives were synthesized and evaluated for carbonic anhydrase inhibitory activity as a target for the treatment of glaucoma, and antibacterial properties for use in chemotherapy. Synthesized compounds were characterized by FT-IR, ¹H NMR, ¹³C NMR and photoluminescence. In vitro inhibitory activities were measured by UV-Vis and some of the compounds were found have greater inhibitory effects than the lead compound sulfanilamide. The correlation between inhibitory activity, biological properties and the physicochemical properties of water solubility and partition coefficients was also investigated. Sulfanilamide derivatives gave intense emissions upon irradiation by UV light and a dimethyl substituted compound and a cyclic analog have photoluminescence quantum yields 42% and 31% and long excited-state lifetimes of 3.92 and 2.91 ns, respectively.

Full text of DOI:10.1016/j.bioorg.2011.02.004

Bioorganic Chemistry 39 (2011) 114–119
Contents lists available at ScienceDirect
Bioorganic Chemistry
journal homepage: www.elsevier.com/locate/bioorg
Synthesis of sulfanilamide derivatives and investigation of in vitro inhibitory
activities and antimicrobial and physical properties
a
Hasan Turkmen a, Gulay Zengin b, , Belkis Buyukkircali
⇑
a Department of Chemistry, Faculty of Science and Literature, Harran University, Sanliurfa 63300, Turkey
b Department of Chemistry, Faculty of Science and Literature, Gaziantep University, Gaziantep 27310, Turkey
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 30 November 2010
Available online 2 March 2011
Novel sulfanilamide derivatives were synthesized and evaluated for carbonic anhydrase inhibitory activ-
ity as a target for the treatment of glaucoma, and antibacterial properties for use in chemotherapy. Syn-
thesized compounds were characterized by FT-IR, 1H NMR, 13C NMR and photoluminescence. In vitro
inhibitory activities were measured by UV–Vis and some of the compounds were found have greater
inhibitory effects than the lead compound sulfanilamide. The correlation between inhibitory activity, bio-
logical properties and the physicochemical properties of water solubility and partition coefficients was
also investigated. Sulfanilamide derivatives gave intense emissions upon irradiation by UV light and a
dimethyl substituted compound and a cyclic analog have photoluminescence quantum yields 42% and
31% and long excited-state lifetimes of 3.92 and 2.91 ns, respectively.
Keywords:
Sulfanilamide
Carbonic anhydrase inhibitor
Antimicrobial activity
Photoluminescence
Ó 2011 Elsevier Inc. All rights reserved.
1. Introduction
ous physicochemical properties was also examined. The results
of these investigations may offer further insight into the treatment
The zinc enzyme carbonic anhydrase (CA, EC 4.2.1.1) has been
the target for drug design for numerous biological applications that
include diuretics, antiglaucoma and antitumor effects [1–3]. Sul-
fonamides of the general formula RSO2NH2, are well known to have
powerful CA inhibitory activity and in particular its use in treat-
ment of glaucoma as a result of the inhibition of CA, and thus caus-
ing the eventual reduction ophthalmic intraocular pressure (IOP).
Also sulfonamides exhibit antibacterial properties playing an
important role in chemotherapy [4,5]. The design and development
of new sulfanilamide derivatives can help determine any structural
requirements for improved biological activity.
The focus of this study was the synthesis and evaluation of sul-
fanilamide derivatives as a target for glaucoma therapy and anti-
microbial activity for potential use in chemotherapy; the general
structure of antibacterial sulfonamides (1), where sulfanilamide
(2) is the parent sulfonamide and is shown in Fig. 1. The design
of the derivatives synthesized aimed to analyze the effect of side
chain length of the tail originating from the nitrogen of the amide
function and the resulting effect of dimethyl substitution on this
chain. Further, a cyclic analog was examined for any apparent
changes in biological activity. Sulfanilamide derivatives were
tested for antimicrobial activity against several bacteria and yeast
and were compared with one another for structure–activity rela-
tionships. The correlation between biological properties and vari-
of glaucoma and may offer promise for antibiotic developments.
In this study sulfanilamide derivatives were examined for CA
inhibition, antimicrobial activity and structure–activity relation-
ships. The photoluminescence properties of these derivatives were
also studied. The chloro-substituted amides 4-(chloroalkanoylami-
no)-benzenesulfonamides 3–5 were synthesized according to the
procedure described elsewhere [6], and is shown here in Scheme 1.
The synthesis of derivative 4-(3-chloro-2,2-dimethylpropanoyla-
mino) (6) is also shown.
Scheme 2 illustrates the synthesis of the derivative 4-(2-
oxopyrrolidinyl)-benzenesulfonamide (7). Intramolecular cycliza-
tion of 4-(chlorobutanoylamino)-benzenesulfonamide (5), in the
presence of potassium carbonate, gave the derivative 4-(2-
oxopyrrolidinyl)-benzenesulfonamide (7).
2. Materials and method
2.1. In vitro inhibition assays
Bovine carbonic anhydrase (CA) enzyme (Bovine type II, Boeh-
ringer Mannheim) was purchased from Aldrich. The enzyme inhib-
itory activities of compounds were expressed as IC50 values, where
IC50 is the molar concentration required to inhibit 50% of enzyme.
In order to determine the inhibitory activities of synthesized com-
pounds, the effect of the enzyme on 4-nitrophenyl acetate hydro-
lysis, with changes in concentration, was examined. The
hydrolysis of 4-nitrophenyl acetate to 4-nitrophenol catalyzed by
⇑
Corresponding author. Fax: +90 342 3601032.
E-mail address: gzengin@gantep.edu.tr (G. Zengin).
0045-2068/$ - see front matter Ó 2011 Elsevier Inc. All rights reserved.
doi:10.1016/j.bioorg.2011.02.004

H. Turkmen et al. / Bioorganic Chemistry 39 (2011) 114–119
115
trations were determined spectrophotometrically by UV–Vis. A
0.01% sample solution was prepared to calculate the division coef-
ficient of the synthesized compound. An aliquot (5 mL) of this
known concentration of sample was taken and same volume of
diethyl ether (5 mL) was added. This mixture was shaken for at
least 5 min and the two phases were separated. The absorbance
of the water phase was measured and after the solvent (diethyl
ether) was evaporated, water was added to dissolve any remaining
sample and then the absorbance of this solution was measured.
The concentration of compounds in ether phase and water phase
was calculated using the absorbance values obtained from UV–
Vis measurements using the previously prepared calibration curve.
RHN
SO2NHR'
H2N
SO2NH2
1
2
Fig. 1. General structure of antibacterial sulfonamides (1) and parent sulfonamide
sulfanilamide (2).
carbonic anhydrase was monitored spectrophotometrically at
400 nm at pH 8.3 with a Hitachi U-1900 UV–Vis Spectrophotome-
ter, interfaced with an IBM compatible PC [7], using a modified lit-
erature procedure [8]. The control (blank) was without inhibitor
(compound) present. Sulfanilamide was used as the standard for
the enzymatic assays.
2.2.2. Determination of solubilities in water
A sample as an effective CA inhibitor should have good solubil-
ity in water. 1% sample solution in deionized water was prepared
and its solubility was calculated. The sample solution was shaken
well in water for at least 30 min at 25 °C. The undissolved sample
was isolated by filtration and the solubility was calculated and gi-
ven as g/100 mL.
2.2. Physical measurement
2.2.1. Determination of the partition coefficient
The ether–water partition coefficients of sulfanilamide (2) and
synthesized compounds 3–7 were measured as described by Han-
sch [9,10]. The calculations for the measurements were carried out
using the equation below:
2.3. Determination of antimicrobial activity
P ¼ Co=Cwð1 ꢀ Þ
a
where P is the ether–water partition coefficient, Co is the concentra-
tion of the compound in the ether phase, Cw is concentration of the
The agar diffusion method using sterile filter paper discs was
used for the screening of antibacterial and antifungal activities of
synthesized sulfanilamide derivatives [13]. Inhibition zones
formed on Mueller Hinton Agar (MHA) and Sabourand Dextrose
Agar (SDA) (expressed as percentage (%) growth inhibition) were
evaluated. Standard paper discs of the antibiotic streptomycin
served as the positive antibacterial controls. Negative controls
were done using paper discs loaded with DMSO. Experiments were
compound in the water phase and
a is the degree dissociation com-
pound in the water phase. The value of ether–water partition coef-
ficient should be at least 0.01 in order to get good dispersion in the
internal eye tissue [11,12].
A calibration curve was plotted using differing concentrations of
sample solutions. The absorbance and wavelength at these concen-
H
N
O
SO2NH2
O
n
n = 1, 2, 3
Cl
Cl
n
Cl
3 n = 1
4 n = 2
5 n = 3
NEM / THF
H2N
SO2NH2
H
O
N
SO2NH2
Cl
Cl
Cl
O
NEM / THF
6
Scheme 1. Synthesis of 4-(2-chloroethanoylamino)-benzenesulfonamide (3, n = 1), 4-(3-chloropropanoylamino)-benzenesulfonamide (4, n = 2), 4-(4-chlorobutanoylamino)-
benzenesulfonamide (5, n = 3) and 4-(3-chloro-2,2-dimethylpropanoylamino)-benzenesulfonamide (6).
H
K2CO3
N
O
SO2NH2
N
SO2NH2
O
O
Cl
5
7
Scheme 2. Synthesis of 4-(2-oxopyrrolidinyl)-benzenesulfonamide (7).

116
H. Turkmen et al. / Bioorganic Chemistry 39 (2011) 114–119
performed in triplicate, and the developing inhibition zones were
compared with those of reference parent compound sulfanilamide.
The following collection of microbes was used: three Gram-po-
sitive (Bacillus cereus EU, Bacillus megaterium DSM 32, Enterococcus
faecalis A10), one Gram-negative (Escherichia coli DM) and one yeast
(Saccharomyces cerevisiae). All microorganisms were provided by
the Microbiology Laboratory Culture Collection, the Department
of Biology, Kahramanmaras Sutcu Imam University, Turkey.
All the bacteria mentioned above were incubated at 37 0.1 °C
for 24 h by inoculation into Nutrient Broth (Difco), and the yeast
studied was incubated at 25 °C in Sabouraud Dextrose Broth
(SDB) (Difco) for 24 h. Mueller Hinton Agar (MHA) (Oxoid) and
Sabourand Dextrose Agar (SDA) sterilized in a flask and cooled to
40–45 °C was distributed over sterilized petri dishes having a
diameter of 9 cm (15 mL) after injecting (0.1 mL) of bacteria and
yeast (105/mL for bacteria and 104/mL for yeast), ensuring homo-
geneous distribution of the food medium over the petri dishes.
20.0 mL THF was added with stirring. A white precipitate of
NEMꢂHCl salt was immediately observed. The reaction mixture
was stirred at room temperature for 24 h, the progress of which
was monitored by TLC (ethyl acetate/methanol 6/1 v/v). The pre-
cipitate was filtered out and the filtrate collected was evaporated
in vacuo to leave a residue. The residue was dissolved in ethyl ace-
tate. The organic extract was washed with 3 M hydrochloric acid
and then saturated sodium bicarbonate solution and then finally
with brine. The extract was dried (MgSO4) and concentrated by
evaporation in vacuo to give a residue. Re-crystallization (ethanol)
afforded 2.84 g (56%) of product as a white solid and was stored in
the refrigerator (4 °C) when not in use: m.p. 183–184 °C; 1H NMR
(300 MHz, d6-DMSO) d 1.31 (s, 6H), 3.88 (s, 2H), 7.15–7.28 (s,
2H), 7.70–7.85 (m, 4H), 9.67 (s, 1H); 13C NMR (75 MHz, d6-DMSO)
d 23.4, 44.1, 51.5, 120.3, 126.8, 139.1, 142.4, 173.8; FTIR (KBr)
3347, 3320, 3110, 2939, 1435, 1666, 1592, 1525, 1435, 1370,
1185, 792 cmꢀ1
.
Sterile filter paper discs (6 mm) injected with 10
lL solutions in
DMSO (80 g/disc) at a concentration of 8.0 mg/mL were placed
l
3.2. 4-(4-Chlorobutanoylamino)-benzenesulfonamide (5)
on the surface of the solid agar medium and were slightly pressed.
Petri dishes prepared as described above were kept for 2 h at 4 °C
to enable prediffusion of the samples into the agar, and subse-
quently samples inoculated with bacteria were incubated at
37 0.1 °C for 24 h and those with yeast were incubated at 25 °C
for 24 h. The inhibition zones formed on the medium were mea-
sured and expressed as percentage (%) growth inhibition. These
studies were performed in triplicate.
4-(Chlorobutanoylamino)-benzenesulfonamide (5) was pre-
pared as described previously [6], where 3.66 g (76%) was obtained
as a white solid from sulfanilamide (3.00 g, 17.42 mmol) in 50.0 mL
THF, NEM (4.41 mL (34.84 mmol)) and 4-chlorobutanoylchloride
(3.90 g, 34.84 mmol) in 20.0 mL THF. The reaction mixture was
stirred at room temperature for 3 h, the progress of which was
monitored by TLC (ethyl acetate/methanol 6/1 v/v). The solid was
recrystallized in ethanol, dried in vacuo and stored in the refriger-
ator (4 °C) and kept in the dark when not in use: m.p. 194–195 °C.
3. Experimental
3.3. 4-(2-Oxopyrrolidinyl)-benzenesulfonamide (7)
Commercially available and/or reagent grade solvents and re-
agents were purchased from Aldrich Co. or Merck and were used
without purification unless otherwise stated. Carbonic anhydrase
enzyme (Bovine type II, Boehringer Mannheim) was purchased
from Aldrich and used as the standard for IC50 measurements. Ana-
lytical thin-layer chromatography (TLC) was performed using alu-
minum-coated Merck DC Alufolien Kieselgel 60 F 724 plates.
All reactions were carried out under an atmosphere of nitrogen
gas. Reaction temperatures were measured either externally, or by
a thermometer inserted into the reaction mixture. Melting points
was recorded using a Stuart Scientific Melting Point Apparatus
and are reported uncorrected.
NMR spectra were recorded on a Bruker AC 300. pH was mea-
sured using a Crison pH Meter, Basic 20. UV–Vis spectra were re-
corded using a Hitachi U-1900 UV–Vis Spectrophotometer and
1 cm optical path quartz cuvette. FTIR spectra were obtained using
a PerkinElmer RXI FTIR Spectrometer. FTIR spectra were obtained
using samples prepared as KBr pellets; samples were dry ground
using a pestle and mortar and then were pressed into transparent
pellets.
To a solution of previously prepared 1.50 g (5.42 mmol) 4-(chlo-
robutanoylamino)-benzenesulfonamide (5) in 100.0 mL acetone,
1.00 g (7.24 mmol) K2CO3 was added with stirring. The reaction
mixture was heated at reflux for 24 h, the progress of which was
monitored by TLC (ethyl acetate/methanol 6/1 v/v). The precipitate
was filtered out and the filtrate collected was evaporated in vacuo
to leave a residue. The residue was dissolved in ethyl acetate. The
organic extract was washed with 3 M hydrochloric acid and then
saturated sodium bicarbonate solution and then finally with brine.
The extract was dried (MgSO4) and concentrated by evaporation in
vacuo to give a residue. Re-crystallization (ethanol) afforded 0.69 g
(53%) of product as a white solid and was stored in the refrigerator
(4 °C) when not in use: m.p. 245–246 °C; 1H NMR (300 MHz, CDCl3)
d 2.00–2.18 (m, 2H), 2.45–2.60 (m, 4H), 7.25–7.33 (m, 2H), 7.70–
7.80 (m, 4H) ppm; 13C NMR (75 MHz, d6-DMSO) 17.7, 32.8, 48.4,
119.1, 126.8, 139.0, 144.9, 175 ppm; FTIR (KBr) 3324, 2977, 2888,
1675, 1460, 1392, 1420, 1334 cmꢀ1
.
The single-photon fluorescence spectra were collected on a
PerkinElmer LS55 luminescence spectrometer. All the samples
were prepared in spectrophotometric grade DMSO and analyzed
in a 1 cm optical path quartz cuvette. The solution concentration
of the compounds in DMSO was 1.0 ꢁ 10ꢀ5 mol Lꢀ1 and the sam-
ples were excited at 257 nm wavelength. The photoluminescence
quantum efficiencies of the compounds and their derivatives were
calculated using 9,10-diphenylantracene as the standard [14].
4. Results and discussion
4.1. Carbonic anhydrase inhibition
The inhibitory activity against the CA enzyme of derivatives
chloro- substituted amides 4-(chloroalkanoylamino)-benzenesulf-
onamides 3–5, 4-(3-chloro-2,2-dimethylpropanoylamino)-ben-
zenesulfonamide (6) and 4-(2-oxopyrrolidinyl)-benzenesulfonamide
(7) are reported herein and compared with that of the parent
sulfonamide sulfanilamide. The inhibitory activities are given in
Table 1. Compounds 3 and 6 showed inhibitory activity similar to
that of sulfanilamide, the lead structure for this class of com-
pounds, and showed the greatest inhibitory activity for these com-
pounds. The number of aliphatic carbon atoms separating the
amino-benzenesulfonamide carbonyl moiety from the terminal
3.1. 4-(3-Chloro-2,2-dimethylpropanoylamino)-benzenesulfonamide
(6)
To a solution of 3.00 g (17.42 mmol) sulfanilamide in 50.0 mL
THF, 4.41 mL (34.84 mmol) NEM was added.
A solution of
4.50 mL (34.84 mmol) 3-chloro 2,2 dimethylpropanoylchloride in

H. Turkmen et al. / Bioorganic Chemistry 39 (2011) 114–119
117
chlorine in derivatives 3, 4 and 5 seems to be important as deriva-
tive 3 being one carbon away from the carbonyl function showed
the greatest enzyme inhibitory activity. Hence a receptor interac-
tion model may include the lipophilic chain length minimum of
one carbon. One carbon chain length showed the greatest activity
and thus this was exploited further in terms of multi-substitution
at this position, though keeping this chain length to a minimum.
The di-substituted derivative 6 fitting this criteria and having a
two carbon chain length was able to show similarly higher activity
than the lead compound sulfanilamide. Replacement of both the
lipophilic chain and chlorine atom with a rigid a 2-oxopyrrolidi-
nyl-unit greatly reduced the inhibitory activity to about half that
of sulfanilamide.
growth inhibition. The results of the antimicrobial activities are
summarized in Table 2.
The synthesized compounds were found to have interesting
antimicrobial activity. The antimicrobial activity observed for all
synthesized compounds were, in general, greater than the refer-
ence compound sulfanilamide. Antimicrobial activity was best ob-
served for Gram-positive bacteria (B. cereus, B. megaterium and E.
faecalis). Only the derivative 4-(chloroethanoylamino)-benzenesul-
fonamide (3) showed activity against Gram-negative bacteria
(E. coli) along with the reference compound sulfanilamide. Addi-
tionally the synthesized compounds were not effective against
the yeast (S. cerevisiae).
A comparison of the antibacterial activity of the chloro-substi-
tuted amides 4-(chloroalkanoylamino)-benzenesulfonamides 3–5
revealed that for Gram-positive bacteria (B. cereus, B. megaterium
and E. faecalis), the shorter the chain length from the carbonyl
group to the chlorine atom the greater the activity, thus activity
decreased with increasing chain length. Only the small chain con-
generic derivative 4-(chloroethanoylamino)-benzenesulfonamide
(3) showed activity against Gram-negative bacteria (E. coli) and
was the same as that obtained for the parent sulfanilamide.
The dimethyl substituted compound 4-(3-chloro 2,2 dim-
ethylpropanoylamino)-benzenesulfonamide (6) had higher anti-
bacterial activity than the straight chain chloro-substituted
amides 4-(chloroalkanoylamino)-benzenesulfonamides 4 and 5,
but had lower activity than small chain congeneric derivative 4-
(chloroethanoylamino)-benzenesulfonamide (3).
4.2. Partition coefficients (P) and solubility
The ether/water partition coefficients (P) for the compounds
synthesized were investigated using the method of Hansch
[9,10], and are given in Table 1. The partition coefficients of synthe-
sized compounds varied between 0.254 and 1.200, and were well
above 0.01 known as the minimum required for good dispersion
in internal eye tissue [11,12]. In order for a drug/compound to be
effective for treating glaucoma, it should have good partition coef-
ficient values together with high inhibitory activity. It can be seen
from Table 1 that all the synthesized compounds had reasonably
good partition coefficient values.
The correlation between partition coefficients (P) and IC50 was
examined. The results showed that for all the synthesized com-
pounds there was no linear relationship between P and IC50 values.
Sulfanilamide has an IC50 value of 72.2 nM. The synthesized com-
pounds, in general, had IC50 values lower than sulfanilamide; only
compounds 3 and 6 had higher IC50 values. It can be seen that the
inhibitory activities and partition coefficients had no bearing on
each other. For example, derivative 7 had IC50 value of 119.9 nM
and a partition coefficient value of 0.990 showing that it had low
inhibitory activity and a high partition coefficient, and likewise
derivative 3 had a IC50 value of 66.6, hence good inhibitory activity
and a low partition coefficient value of 0.436.
When a c-lactam ring replaced the chloroalkanoylamino chain
as for 4-(2-oxopyrrolidinyl)-benzenesulfonamide (7) antibacterial
activity was retained for Gram-positive bacteria (B. cereus, B. mega-
terium and E. faecalis), being lower than the small chain chloro-
substituted amides 4-(chloroalkanoylamino)-benzenesulfonamide
3 and higher than two larger congeneric derivatives chloro-substi-
tuted amides 4-(chloroalkanoylamino)-benzenesulfonamides
4
and 5. This -lactam derivative (7) had higher antibacterial activity
c
against Gram-positive than the dimethyl substituted compound
(6). Further no antimicrobial activity was observed for this com-
pound
c-lactam derivative (7) against Gram-negative bacteria
(E. coli).
The correlation between solubility in water and IC50 was also
examined. The results showed that for all the synthesized com-
pounds there was no linear relationship between solubility in
water and IC50 values. A compound with good inhibitory activity
may have either high solubility or low solubility in water. For
example, compound 6 has lower inhibitory activity than derivative
3, however for the solubility in water, the reverse was observed.
Further derivative 6 has a higher inhibitory activity and solubility
in water than 7.
The results showed that the synthesized compounds possessed
antibacterial activity against Gram-positive and only one com-
pound against Gram-negative bacteria. Antifungal activity was
not observed for any of these compounds. Aliphatic chain length
was an important component being more effective when kept to
minimum length as for compound 3. Dimethyl substitution in this
chain as in compound 6 allowed for high activity to be retained
though lower than that observed for the shortest chain (3). The
introduction of a c-lactam ring in place of this chain, as for com-
pound 7, did not adversely affect the antibacterial activity, but in
fact kept the activity to a high level. These observations may be
used to further develop antimicrobial agent.
4.3. Antimicrobial activity
The test solutions were prepared in DMSO. The inhibition zones
on the medium were measured and expressed as percentage (%)
4.4. Structure–activity relationships
Lipophilicity of compounds has an important effect on their bio-
logical activity [12,15]. It is expressed as log P, the octanol/water
partition coefficient, and high values indicate good permeation of
compounds through lipid layers of cell membranes. The prediction
of lipophilicity and other physicochemical properties such as molar
weight (MW), molecular volume (MV), molecular refractivity (MR)
for compounds 2–7 was calculated using HyperChem Software in
an attempt to correlate physicochemical properties of the com-
pounds with their antimicrobial activity [16]. The physicochemical
properties MW, MV, MR and log P of the compounds studied are
presented in Table 2.
Table 1
Inhibitory activities of carbonic anhydrase by different sulfanilamide derivatives.
a
Compound IC50
(nM)
Partition coefficient (P) at Solubilities in water (g/
pH = 7.2
100 cm3)
2
3
4
5
6
7
72.2
66.6
78.3
89.1
69.4
119.9
0.082
0.436
0.370
0.254
1.200
0.990
0.75
0.30
0.10
0.05
0.50
0.15
a
In vitro studies as effects on carbonic anhydrase isozyme II (CA-II).

118
H. Turkmen et al. / Bioorganic Chemistry 39 (2011) 114–119
Table 2
Antimicrobial activity data and selected physiochemical properties for sulfanilamide and their derivatives.
Entitya
Microorganismc
Physiochemical properties
0
0
B. cereus
B. megaterium
E. fecalis
E. coli
MW
log P
MV (AÅ3)
MR (AÅ3)
Streptomycinb
16
24
35
26
24
31
33
20
21
31
19
16
24
28
18
19
38
28
26
31
33
11
24
24
–
–
–
NA
NA
NA
NA
2
3
4
5
6
7
172.20
248.68
262.71
276.74
290.76
240.28
498.44
658.22
704.62
767.60
793.09
675.07
47.76
61.96
66.66
71.41
75.73
64.99
ꢀ1.98
ꢀ1.56
ꢀ1.38
ꢀ1.13
ꢀ0.15
ꢀ1.76
–
a
b
c
Entity refers to compounds.
Standard compound.
% growth inhibition; – denotes no activity; S. cereviciae (not shown here) was also used, however all entities showed no antifungal activity against S. cerevisiae.
Interestingly, of the chloro-substituted amides 4-(chloro-
800
alkanoylamino)-benzenesulfonamides 3–5, compound 3 has the
highest lipophilicity, and among all synthesized compounds the ri-
gid 2-oxopyrrolidinyl- compound 7 has the highest lipophilicity.
The antimicrobial activity for these two compounds (3 and 7)
showed a similar trend where antimicrobial activities were also
the highest for these compounds. Compounds 3 and 7 have both
comparable lipophilicity and antimicrobial activity.
The chloro-substituted amides 4-(chloroalkanoylamino)-ben-
zenesulfonamides 3–5 showed that as lipophilicity decreased, anti-
microbial activity decreased. Further, antimicrobial activity against
E. coli was only observed for the smallest and most lipophilic com-
pound 3.
The dimethyl substituted compound 6 had high antimicrobial
activity but low lipophilic character, though the rigid 2-oxopyrro-
lidinyl-analogue 7 follows the trend of increasing antimicrobial
activity with increasing lipophilic character; compound 7 is more
lipophilic and had greater antimicrobial activity than the smaller
compound 6. In general, the results showed there was a depen-
dency between biological activity and lipophilicity, where antimi-
crobial activity increased with increasing lipophilicity. Additionally
antimicrobial activity increased with decreasing MV with the
exception of compound 6; for compound 6 molecular size as vol-
ume appears to play an adverse role on antimicrobial activity,
where for this compound size has a dominating role on antimicro-
bial activity. MR as with lipophilicity, is also a molecular descriptor
used to relate chemical structure to observed behavior. It can be
seen from Table 2 that, in general, MR decreased with increasing
lipophilicity, and thus, antimicrobial activity increased with
decreasing MR.
Ex. of 6
Ex. of 5
Ex. of 4
Ex. of 3
Ex. of 2
Ex. of 7
Em. of 6
Em. of 5
Em. of 4
Em. of 3
Em. of 2
Em. of 7
700
600
500
400
300
200
100
0
160
220
280
340
400
460
520
580
Wavelength (nm)
Fig. 2. Photoluminescence spectra of compounds in DMSO; samples were excited at
257 nm.
Table 3
Photoluminescence data for compounds.
Entity kmax Ex (nm)
In Ex
538
kmax Em (nm)
In Em /f (%) sf (ns)
2
3
4
5
6
7
261
(229;241;271)
266
(231;242;255)
272
(232;243;256)
278
(233;244;257)
282
(234;245;258)
258
381
(360;406;435)
406
(379;434)
408
(382;435)
410
(384;437)
412
(386;439)
378
531
599
631
664
731
498
33
36
38
39
42
31
3.06
3.37
3.50
3.64
3.92
2.91
607
639
673
741
504
The synthesized compounds all possessed carbonyl groups and
possible hydrogen bonding with the active cell components may
be influential for antimicrobial activity, resulting in the interfer-
ence and disruption of normal cell processes.
(226;237;269)
(358;402;433)
kmax Ex: maximum excitation wavelength; In Ex: maximum excitation intensity.
kmax Em: maximum emission wavelength; In Em: maximum emission intensity.
/f: quantum yield; sf: excited-state lifetime.
4.5. Fluorescence measurements
the para-position of the derivatives caused a decrease in the inten-
sity of the main peaks and shifted to lower emission wavelength.
The photoluminescence data are summarized in Table 3. The
photoluminescent properties of these compounds may indicate
great potential for numerous optical applications and for medicinal
biomarkers.
Absorption and photoluminescence spectra were studied for
solutions compounds excited at 257 nm. The most striking feature
was that compounds and their derivative gave an intense emission
upon irradiation by UV light. The photoluminescence spectrum of
compounds in DMSO is shown in Fig. 2. Maximum luminescent
intensity was observed at 381 nm and the full width at half maxi-
mum was 117 nm for compound 2. Compound 2 exhibited a pho-
toluminescence quantum yield of 33% and a long excited-state
lifetime of 3.06 ns. Addition of more electron donating groups at
the para-position of the derivatives caused an increase in the
intensity of the main peaks and shifted to higher emission wave-
length. Also, addition of more electron withdrawing groups at
5. Conclusion
In vitro inhibitory activities of the synthesized compounds ex-
pressed as IC50 were investigated by using a UV–Vis spectropho-
tometer. Partition coefficients of the synthesized compounds

H. Turkmen et al. / Bioorganic Chemistry 39 (2011) 114–119
119
were also studied. Some of the synthesised compounds were found
to be comparable or more potent than sulfanilamide. The partition
coefficient values revealed good dispersion but did not follow any
clear cut pattern in relation to their inhibitory activities. The solu-
bility in water of the synthesized compounds were examined and
correlated with their inhibitory activities. In general, water solubil-
ities were erratic and there was no linear relationship between sol-
ubility in water and IC50 values. The antimicrobial activity
observed for all synthesized compounds were in general greater
than the reference compound sulfanilamide. Antimicrobial activity
was best observed for Gram-positive bacteria and only one com-
pound showed activity against Gram-negative bacteria (E. coli)
along with the reference compound sulfanilamide. None of the
synthesized compounds were effective against yeast. In general,
the results showed there was a dependency between biological
activity and lipophilicity, where antimicrobial activity increased
with increasing lipophilicity.
to Prof. Dr. Metin Dıg˘rak from the Department of Biology at Kahr-
amanmaras Sutcu Imam University for his help in determining the
biological activity. Also the authors would like to thank Depart-
ments of Chemistry at Harran University and Gaziantep University.
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The authors wish to thank Harran University for the financial
support (HUBAK Project No. 874). The authors are very grateful