Novel arylhydrazone derivatives bearing a rhodanine moiety: Synthesis and evaluation of their antibacterial activities

Article abstract of DOI:10.1007/s12272-013-0214-3

A series of arylhydrazone derivatives bearing a rhodanine moiety have been synthesized, characterized, and evaluated as antibacterial agents. Some of these compounds showed potent antibacterial activities against several different strains of Gram-positive bacteria, including multidrug-resistant clinical isolates. Of the compounds tested, IIk and IIIk were identified as the most effective, with minimum inhibitory concentration values of 2-4 μg/mL against multidrug-resistant Gram-positive organisms, including methicillin-resistant and quinolone-resistant Staphylococcus aureus. None of the compounds exhibited any activity against the Gram-negative bacteria Escherichia coli 1356 at 64 μg/mL.

Full text of DOI:10.1007/s12272-013-0214-3

Arch. Pharm. Res.
DOI 10.1007/s12272-013-0214-3
RESEARCH ARTICLE
Novel arylhydrazone derivatives bearing a rhodanine moiety:
synthesis and evaluation of their antibacterial activities
•
Wei Li Chang-Ji Zheng Liang-Peng Sun
•
•
•
Ming-Xia Song Yan Wu Yin-Jing Li
•
•
•
Yi Liu Hu-Ri Piao
Received: 14 May 2013 / Accepted: 10 July 2013
Ó The Pharmaceutical Society of Korea 2013
Abstract A series of arylhydrazone derivatives bearing a
rhodanine moiety have been synthesized, characterized, and
evaluated as antibacterial agents. Some of these compounds
showed potent antibacterial activities against several dif-
ferent strains of Gram-positive bacteria, including multi-
drug-resistant clinical isolates. Of the compounds tested, IIk
and IIIk were identified as the most effective, with minimum
inhibitory concentration values of 2–4 lg/mL against mul-
tidrug-resistant Gram-positive organisms, including methi-
cillin-resistant and quinolone-resistant Staphylococcus
aureus. None of the compounds exhibited any activity
against the Gram-negative bacteria Escherichia coli 1356 at
64 lg/mL.
failure as well as other complications. A large number of
different antibiotics have been developed during the course
of the last 70 years and shown to be effective against a
variety of infectious diseases. Unfortunately, however,
Gram-positive pathogens such as Staphylococcus aureus,
Enterococcus faecalis, Enterococcus faecium, and Strep-
tococcus pneumoniae are becoming increasingly resistant
to most of the existing antibiotics (Khalaj et al. 2011), and
Methicillin-resistant Staphylococcus aureus (MRSA) and
Vancomycin-resistant enterococci (VRE) in particular have
had a major impact on infections in hospitals and com-
munities throughout the world (Appelbaum 2006; Zetola
et al. 2005). Although antibiotic-resistant organisms con-
tinue to become increasingly commonplace, the rate of
discovery of new antibacterial agents has decreased (Walsh
2000). For this reason, there is an urgent need for new
antibacterial agents that are capable of treating resistant
bacterial strains.
Keywords Arylhydrazone Á Rhodanine Á
Antibacterial activity Á Methicillin-resistant
Staphylococcus aureus Á Quinolone-resistant
Staphylococcus aureus
A large number of arylhydrazone derivatives have been
reported in the literature with a diverse range of pharmaco-
logical properties, including antinociceptive (Cunha et al.
2002; Silva et al. 2004), antiviral (Jin et al. 2010), anti-
inflammatory (Silva et al. 2010), antiplatelet (Lima et al.
2008), and antibacterial (Wang et al. 2012) activities.
Although the hydrazone and Schiff base moieties of aryl-
hydrazones can be unstable, arylhydrazones themselves
have long been regarded as privileged structures, and have
been employed on several occasions to improve chemical
stability during the design of new antibacterial agents. A-
rylhydrazones have attracted considerable levels of attention
as a result of the physical, chemical, and biological activities
they derive from their unique structures, and they are also
known to exhibit a broad range of biological properties,
including antimicrobial activities against a variety of dif-
ferent bacteria (Rasras et al. 2010; Metwally et al. 2006).
Introduction
Successive annual increases in the number of infections
caused by bacteria that are resistant to one or more of the
available classes of antibiotics poses a significant threat to
human health (Beekmann et al. 2005; Fajdetic et al. 2011)
because these resistant strains could lead to treatment
W. Li Á C.-J. Zheng Á L.-P. Sun Á M.-X. Song Á Y. Wu Á
Y.-J. Li Á Y. Liu Á H.-R. Piao (&)
Key Laboratory of Natural Resources and Functional Molecules
of the Changbai Mountain, Affiliated Ministry of Education,
Yanbian University College of Pharmacy, Yanji 133002,
Jilin, People’s Republic of China
e-mail: piaohuri@yahoo.com.cn; piaohuri@aliyun.com
123

W. Li et al.
In recent years, rhodanine and its derivatives have
appeared in a large number of research reports focused on
medicinal chemistry and drug discovery because they
possess a wide variety of biological properties, including
anticonvulsant (Chauhan et al. 2013), antibacterial (Zheng
et al. 2012), antimalarial (Takasu et al. 2002), antiviral, and
anti-diabetic (Ohishi et al. 1990) activities. The antimi-
crobial activities of rhodanines have been known for over
50 years, and several attempts have been made to design
and synthesize anti-bacterial agents based on this unique
heterocycle (Habib et al. 1997). In our previous work
(Chen et al. 2010; Jin et al. 2012; Song et al. 2012), we
found that several rhodanine-3-fatty acid derivatives
showed strong activities against Gram-positive bacterial
strains (Fig. 1). Thus, as part of our ongoing studies
towards the development of novel antibacterial agents,
herein we report the design, synthesis, and antimicrobial
evaluation of a series of arylhydrazone derivatives bearing
a rhodanine moiety as efficient antimicrobial agents.
Reaction courses were monitored by TLC on silica gel-pre-
coated F254 Merck plates. Developed plates were examined
with UV lamps (254 nm). IR spectra were recorded (in KBr)
on a FTIR1730. 1H NMR and 13C NMR spectra were
recorded in pure DMSO-d6 on Bruker NMR spectrometers at
300 and 75 MHz respectively using tetramethylsilane
(TMS) as internal standard. Chemical shifts were expressed
in d, ppm. Mass spectra were measured on an HP1100LC
(Agilent Technologies, USA). The major chemicals were
purchased from Sigma-Aldrich and Fluka.
General procedure for the preparation
of rhodanine-3-fatty acid
In a round-bottomed flask equipped with a magnetic stirrer,
amino acid 4 (0.03 mol) was dissolved with sodium
hydroxide (0.03 mol) in water (25 mL). Then, carbon
disulfide (0.03 mol) was added to the reaction mixture,
which was stirred vigorously overnight. An aqueous solu-
tion of sodium chloroacetate (0.03 mol) was added and
stirring was continued at 23 °C for 3 h. Then the reaction
mixture was acidified with dilute HCl until pH 1.0 and
refluxed overnight. The reaction mixture was neutralized
with saturated NaHCO3 solution. The resultant solution
was acidified again with dilute HCl. The cyclized product
was extracted in ethyl acetate, dried over anhydrous
sodium sulfate and evaporated under vacuum and the res-
idue was purified by column chromatography (dichloro-
methane/methanol, 40:1) (Hardej et al. 2010; Bursavich
et al. 2007).
Chemistry
The reaction sequences employed for the synthesis of the
target compounds are shown in Scheme 1. The synthesis of
the aromatic hydrazines (3a–p) proceeded via the forma-
tion of the aromatic esters (2a–p), which were constructed
from the corresponding acids by acid-catalyzed esterifica-
tion. The aromatic esters (2a–p) were then converted to the
aromatic hydrazines by their reaction with hydrazine
hydrate in ethanol at reflux. The intermediates 5 were
obtained in good yields either via the Knoevenagel con-
densation of terephthalaldehyde with rhodanine-3-fatty
acid 4 or from different amino acids according to a method
previously described in the literature (Chen et al. 2010; Jin
et al. 2012; Song et al. 2012). The reaction of compounds
3a–p with different aldehydes 5 in alcohol afforded the
corresponding Schiff bases I–V. The structures of the
synthesized compounds were confirmed by Fourier trans-
form infrared, 1H NMR, 13C NMR, and mass spectroscopic
analyses.
General synthetic procedure for the key intermediates 5
A mixture of terephthalaldehyde (2.68 g 0.02 mol) and
rhodanine-3-fatty acid (0.01 mmol) reacted in ethanol
under reflux for 6–7 h. The reaction was catalyzed by drops
of acetic acid and piperidine. After cooling, the solvent was
removed under reduced pressure, dried, and purified by
silica gel column chromatography (dichloromethane/
methanol, 100:1) (Tihomir et al. 2010; Wang et al. 2008).
General synthetic procedure for the target
compounds I–V
Experimental section
In a round-bottomed flask equipped with a magnetic stirrer,
Melting points were determined in open glass capillaries in
an electrical melting point apparatus and are uncorrected.
intermediates 5 (0.001 mol) and acylhydrazine 3a–p
(0.001 mol) were dissolved in ethanol (5 mL). The reaction
Fig. 1 Previously reported
antibacterial agents with a
rhodanine moiety
O
O
O
S
O
H
COO
S
H
COO
S
N
N
F
l
C
l
C
O
O
123

Novel arylhydrazone derivatives bearing a rhodanine moiety
Scheme 1 Synthetic scheme
for the synthesis of compounds
O
O
COOH
R
COOH
R
CHO
iii
I–V. Reagents and conditions:
(i) H2SO4, EtOH, 110 °C,
reflux, 12–24 h; (ii) hydrazine
hydrate, EtOH, 100 °C, reflux,
12 h; (iii) Piperidine, AcOH,
EtOH, 40 °C, 6–7 h; (iv) EtOH,
50 °C, 4–6 h
N
S
+
N
S
S
H
O C
OHC
S
4
5
CONHNH2
3a-p
ii
i
COOEt
2a-p
COOH
1a-p
r
A
Ar
r
A
v
i
O
-
-
-
a
b
c
d
e
f
uran- -
2
(
(
)
i
j
k
H4
H4
2
3
H
C6
C6
C6
C6
C6
C
C
Ar=
f
l
y
H3
R
)
C6H5
H4
C6
naphthalen-1-yl
3
O
r
r
N
-
(
)
)
(
4
)
H4 4 B
l
C
-
(
H4
l
H4 3 B
N
S
COOH
r
A
N
m
n
o
-
(
4
OC
( -
)
)
)
3
H
H4
3
l
C6
C
H
-
( -
(
S
C6H4 2 Cl
pridiny-4-yl
-
4
)
(
H4
)
H
(
-
I V
H4 3 N
C6
C6
C
C6
O2
g
h
3
(
3)2)
H
OC
H3 2 3
,
p
pridiny-3-yl
H
C
H
C
3
3
=
R
:
:
V
I
:
III
:
IV
H
:
II
N
H
3C
H
C
3
H
(S)-2-((Z)-5-(4-((E)-(2-(4-Chlorobenzoyl)hydrazono)
mixture was stirred at 40–50 °C, until the completion of the
reaction as evidenced by TLC. After the completion of the
reaction, excess solvent was removed under reduced
pressure. The compound was extracted into dichloro-
methane, concentrated and purified by column chroma-
tography (dichloromethane/methanol, 50:1). The yield,
melting point and spectral data of each compound are given
below.
methyl)benzylidene)-4-oxo-2-thioxothiazolidin-3-yl)-3-
phenylpropanoic acid (Ic)
Yield 83 %; m.p. 228–230 °C. IR (KBr) cm-1: 3431 (OH),
1718 (C=O). 1H NMR (DMSO-d6, 300 MHz, ppm): d 3.42
(d, J = 9.0 Hz, 2H, CH2), 5.88 (s, 1H, CH), 7.14–7.96 (m,
14H, Ar–H), 7.89 (s, 1H, Ph=CH), 8.47 (s, 1H, N=CH),
12.09 (s, 1H, NH), 13.46 (s, 1H, COOH). 13C NMR
(DMSO-d6, 75 MHz, ppm): d 192.61, 168.66, 166.44,
162.28, 146.73, 136.49, 133.91, 133.02, 132.24, 131.53,
131.34, 129.76, 128.97, 128.28, 127.93, 127.75, 126.73,
125.72, 121.28, 58.18, 56.02, 18.54. MS (EI) m/z calcd for
C27H20ClN3O4S2 (M?) 549.06, found 550 (MH?).
(S)-2-((Z)-5-(4-((E)-(2-(Furan-2-carbonyl)hydrazono)
methyl)benzylidene)-4-oxo-2-thioxothiazolidin-3-yl)-3-
phenylpropanoic acid (Ia)
Yield 85 %; m.p. 188–190 °C. IR (KBr) cm-1: 3419 (OH),
1707 (C=O). 1H NMR (DMSO-d6, 300 MHz, ppm): d 3.49
(d, J = 9.0 Hz, 2H, CH2), 5.86 (s, 1H, CH), 6.70–7.95 (m,
12H, Ar–H), 7.83 (s, 1H, Ph=CH), 8.46 (s, 1H, N=CH),
12.03 (s, 1H, NH). MS (EI) m/z calcd for C25H19N3O5S2
(M?) 505.08, found 506 (MH?).
(S)-2-((Z)-5-(4-((E)-(2-(1-Naphthoyl)hydrazono)
methyl)benzylidene)-4-oxo-2-thioxothiazolidin-3-yl)-3-
phenylpropanoic acid (Id)
Yield 83 %; m.p. 176–178 °C. IR (KBr) cm-1: 3434 (OH),
1707 (C=O). 1H NMR (DMSO-d6, 300 MHz, ppm): d 3.52
(d, J = 9.0 Hz, 2H, CH2), 5.78 (s, 1H, CH), 7.14–8.77 (m,
16H, Ar–H), 7.90 (s, 1H, Ph=CH), 8.48 (s, 1H, N=CH), 12.03
(s, 1H, NH), 13.45 (s, 1H, COOH). MS (EI) m/z calcd for
C31H23N3O4S2 (M?) 565.11, found 566 (MH?).
(S)-2-((Z)-5-(4-((E)-(2-Benzoylhydrazono)
methyl)benzylidene)-4-oxo-2-thioxothiazolidin-3-yl)-3-
phenylpropanoic acid (Ib)
Yield 86 %; m.p. 178–180 °C. IR (KBr) cm-1: 3449
(OH), 1708 (C=O). 1H NMR (DMSO-d6, 300 MHz,
ppm): d 3.50 (d, J = 9.0 Hz, 2H, CH2), 5.88 (s, 1H, CH),
7.15–8.20 (m, 14H, Ar–H), 7.83 (s, 1H, Ph=CH), 8.36 (s,
1H, N=CH), 12.19 (s, 1H, NH). MS (EI) m/z calcd for
C27H21N3O4S2 (M?) 515.10, found 516 (MH?).
(S)-2-((Z)-5-(4-((E)-(2-(3-Chlorobenzoyl)hydrazono)
methyl)benzylidene)-4-oxo-2-thioxothiazolidin-3-yl)-3-
phenylpropanoic acid (Ie)
Yield 93 %; m.p. 164–166 °C. IR (KBr) cm-1: 3416 (OH),
1
1703 (C=O). H NMR (DMSO-d6, 75 MHz, ppm): d 3.51
123

W. Li et al.
(S)-2-((Z)-5-(4-((E)-(2-(3-Methylbenzoyl)hydrazono)
(d, J = 9.0 Hz, 2H, CH2), 5.88 (s, 1H, CH), 7.16–7.97 (m,
13H, Ar–H), 7.89 (s, 1H, Ph=CH), 8.46 (s, 1H, N=CH),
12.10 (s, 1H, NH). 13C NMR (DMSO-d6, 75 MHz, ppm): d
193.06, 169.18, 166.92, 162.26, 147.41, 145.37, 136.97,
135.62, 134.43, 133.79, 133.48, 132.20, 131.81, 130.99,
129.47, 128.76, 128.44, 127.87, 127.22, 127.00, 121.76,
58.65, 33.58. MS (EI) m/z calcd for C27H20ClN3O4S2 (M?)
549.06, found 550 (MH?).
methyl)benzylidene)-4-oxo-2-thioxothiazolidin-3-yl)-3-
phenylpropanoic acid (Ij)
Yield 86 %; m.p. 148–150 °C. IR (KBr) cm-1: 3416 (OH),
1709 (C=O). 1H NMR (DMSO-d6, 300 MHz, ppm): d 2.39
(s, 1H, CH3), 3.51 (d, J = 9.0 Hz, 2H, CH2), 5.82 (s, 1H,
CH), 7.13–7.88 (m, 13H, Ar–H), 7.80 (s, 1H, Ph=CH), 8.48
(s, 1H, N=CH), 11.99 (s, 1H, NH). MS (EI) m/z calcd for
C28H23N3O4S2 (M?) 529.11, found 530 (MH?).
(S)-2-((Z)-5-(4-((E)-(2-(2-Chlorobenzoyl)hydrazono)
methyl)benzylidene)-4-oxo-2-thioxothiazolidin-3-yl)-3-
phenylpropanoic acid (If)
(S)-2-((Z)-5-(4-((E)-(2-(4-Bromobenzoyl)hydrazono)
methyl)benzylidene)-4-oxo-2-thioxothiazolidin-3-yl)-3-
phenylpropanoic acid (Ik)
Yield 84 %; m.p. 126–128 °C. IR (KBr) cm-1: 3428 (OH),
1712 (C=O). 1H NMR (DMSO-d6, 300 MHz, ppm): d 3.50
(d, J = 9.0 Hz, 2H, CH2), 5.74 (s, 1H, CH), 7.14–7.88 (m,
16H, Ar–H), 8.29 (s, 1H, Ph=CH), 9.64 (s, 1H, N=CH), 12.03
(s, 1H, NH), 13.45 (s, 1H, COOH). MS (EI) m/z calcd for
C27H20ClN3O4S2 (M?) 549.06, found 550 (MH?).
Yield 86 %; m.p. 256–258 °C. IR (KBr) cm-1: 3439 (OH),
1713 (C=O). 1H NMR (DMSO-d6, 300 MHz, ppm): d 3.44
(d, J = 9.0 Hz, 2H, CH2), 5.88 (s, 1H, CH), 7.15–7.89 (m,
13H, Ar–H), 7.82 (s, 1H, Ph=CH), 8.47 (s, 1H, N=CH), 12.07
(s, 1H, NH), 13.45 (s, 1H, COOH). 13C NMR (DMSO-d6,
75 MHz, ppm): d 192.62, 168.69, 167.18, 166.45, 146.15,
142.01, 136.79, 136.78, 136.50, 133.75, 133.08, 131.35,
129.00, 128.29, 127.84, 127.70, 126.75, 123.36, 121.17,
58.18, 21.04. MS (EI) m/z calcd for C27H20BrN3O4S2 (M?)
595.01, found 596 (MH?).
(S)-2-((Z)-5-(4-((E)-(2-(3-Nitrobenzoyl)hydrazono)
methyl)benzylidene)-4-oxo-2-thioxothiazolidin-3-yl)-3-
phenylpropanoic acid (Ig)
Yield 95 %; m.p. 148–150 °C. IR (KBr) cm-1: 3416 (OH),
1704 (C=O). 1H NMR (DMSO-d6, 300 MHz, ppm): d 3.52
(d, J = 9.0 Hz, 2H, CH2), 5.89 (s, 1H, CH), 7.16–8.76 (m,
16H, Ar–H), 7.83 (s, 1H, Ph=CH), 8.46 (s, 1H, N=CH),
12.33 (s, 1H, NH). MS (EI) m/z calcd for C27H20N4O6S2
(M?) 560.08, found 561 (MH?).
(S)-2-((Z)-5-(4-((E)-(2-(3-Bromobenzoyl)hydrazono)
methyl)benzylidene)-4-oxo-2-thioxothiazolidin-3-yl)-3-
phenylpropanoic acid (Il)
Yield 82 %; m.p. 126–128 °C. IR (KBr) cm-1: 3435 (OH),
1703 (C=O). 1H NMR (DMSO-d6, 300 MHz, ppm): d 3.52
(d, J = 9.0 Hz, 2H, CH2), 5.88 (s, 1H, CH), 7.14–8.10 (m,
13H, Ar–H), 7.82 (s, 1H, Ph=CH), 8.47 (s, 1H, N=CH),
12.09 (s, 1H, NH). MS (EI) m/z calcd for C27H20BrN3O4S2
(M?) 595.01, found 596 (MH?).
(S)-2-((Z)-5-(4-((E)-(2-Nicotinoylhydrazono)
methyl)benzylidene)-4-oxo-2-thioxothiazolidin-3-yl)-3-
phenylpropanoic acid (Ih)
Yield 86 %; m.p. 178–180 °C. IR (KBr) cm-1: 3429 (OH),
1713 (C=O). 1H NMR (DMSO-d6, 300 MHz, ppm): d 3.43
(d, J = 9.0 Hz, 2H, CH2), 5.88 (s, 1H, CH), 7.14–9.07 (m,
13H, Ar–H), 7.82 (s, 1H, Ph=CH), 8.47 (s, 1H, N=CH),
12.20 (s, 1H, NH). MS (EI) m/z calcd for C26H20N4O4S2
(M?) 516.09, found 517 (MH?).
(S)-2-((Z)-5-(4-((E)-(2-(4-Methoxybenzoyl)hydrazono)
methyl)benzylidene)-4-oxo-2-thioxothiazolidin-3-yl)-3-
phenylpropanoic acid (Im)
Yield 79 %; m.p. 230–232 °C. IR (KBr) cm-1: 3417
(OH), 1689 (C=O). 1H NMR (DMSO-d6, 300 MHz, ppm):
d 3.50 (d, J = 9.0 Hz, 2H, CH2), 3.83 (s, 1H, CH3), 5.88
(s, 1H, CH), 7.05–7.93 (m, 13H, Ar–H), 7.81 (s, 1H,
Ph=CH), 8.47 (s, 1H, N=CH), 11.88 (s, 1H, NH), 13.44 (s,
1H, COOH). 13C NMR (DMSO-d6, 75 MHz, ppm): d
193.08, 169.19, 166.93, 163.21, 162.59, 146.20, 137.34,
136.97, 134.15, 133.57, 131.83, 130.12, 129.47, 128.77,
128.25, 127.22, 125.67, 121.57, 114.21, 58.66, 55.90,
33.59. MS (EI) m/z calcd for C28H23N3O5S2 (M?) 545.11,
found 546 (MH?).
(S)-2-((Z)-5-(4-((E)-(2-(2-Methylbenzoyl)hydrazono)
methyl)benzylidene)-4-oxo-2-thioxothiazolidin-3-yl)-3-
phenylpropanoic acid (Ii)
Yield 91 %; m.p. 178–180 °C. IR (KBr) cm-1: 3424 (OH),
1713 (C=O). 1H NMR (DMSO-d6, 300 MHz, ppm): d 2.37
(s, 1H, CH3), 3.51 (d, J = 9.0 Hz, 2H, CH2), 5.88 (s, 1H,
CH), 7.14–7.86 (m, 13H, Ar–H), 7.83 (s, 1H, Ph=CH), 8.31
(s, 1H, N=CH), 11.85 (s, 1H, NH). MS (EI) m/z calcd for
C28H23N3O4S2 (M?) 529.11, found 530 (MH?).
123

Novel arylhydrazone derivatives bearing a rhodanine moiety
(S)-2-((Z)-5-(4-((E)-(2-Isonicotinoylhydrazono)
methyl)benzylidene)-4-oxo-2-thioxothiazolidin-3-yl)-3-
phenylpropanoic acid (In)
137.24, 137.02, 134.53, 133.60, 132.33, 131.76, 130.09,
129.08, 128.43, 122.12, 56.38, 25.28, 23.34, 22.41. MS
(EI) m/z calcd for C24H22ClN3O4S2 (M?) 515.07, found
516 (MH?).
Yield 80 %; m.p. 256–258 °C. IR (KBr) cm-1: 3433 (OH),
1
1706 (C=O). H NMR (DMSO-d6, 300 MHz, ppm): d 3.52
(R)-2-((Z)-5-(4-((E)-(2-(1-Naphthoyl)hydrazono)
methyl)benzylidene)-4-oxo-2-thioxothiazolidin-3-yl)-4-
methylpentanoic acid (IId)
(d, J = 9.0 Hz, 2H, CH2), 5.88 (s, 1H, CH), 7.16–8.80 (m,
13H, Ar–H), 7.83 (s, 1H, Ph=CH), 8.49 (s, 1H, N=CH),
12.22 (s, 1H, NH), 13.46 (s, 1H, COOH). MS (EI) m/z calcd
for C26H20N4O4S2 (M?) 516.09, found 517 (MH?).
Yield 87 %; m.p. 268–270 °C. IR (KBr) cm-1: 3326 (OH),
1695 (C=O). 1H NMR (DMSO-d6, 300 MHz, ppm): d 0.93
(d, J = 9.0 Hz, 3H, CH3), 0.98 (d, J = 9.0 Hz, 3H, CH3),
1.55 (m, 1H, CH), 2.08–2.26 (m, 2H, CH2), 5.66 (m, 1H,
CH), 7.43–8.29 (m, 12H, Ar–H), 8.44 (s, 1H, N=CH),
12.24 (s, 1H, NH), 13.41 (s, 1H, COOH). MS (EI) m/z calcd
for C28H25N3O4S2 (M?) 531.13, found 532 (MH?).
(S)-2-((Z)-5-(4-((E)-(2-(4-Methylbenzoyl)hydrazono)
methyl)benzylidene)-4-oxo-2-thioxothiazolidin-3-yl)-3-
phenylpropanoic acid (Io)
Yield 81 %; m.p. 242–244 °C. IR (KBr) cm-1: 3426 (OH),
1702 (C=O). 1H NMR (DMSO-d6, 300 MHz, ppm): d 2.37
(s, 3H, CH3), 3.52 (d, J = 9.0 Hz, 2H, CH2), 5.88 (s, 1H,
CH), 7.15–7.85 (m, 13H, Ar–H), 7.82 (s, 1H, Ph=CH), 8.48
(s, 1H, N=CH), 11.93 (s, 1H, NH), 13.43 (s, 1H, COOH).
13C NMR (DMSO-d6, 75 MHz, ppm): d 192.61, 168.66,
166.44, 162.28, 146.73, 136.49, 133.91, 133.02, 132.24,
131.53, 131.34, 129.76, 128.97, 128.28, 127.93, 127.75,
126.73, 125.72, 121.28, 58.18, 56.02, 18.54. MS (EI)
m/z calcd for C28H23N3O4S2 (M?) 529.11, found 530 (MH?).
(R)-2-((Z)-5-(4-((E)-(2-(4-Bromobenzoyl)hydrazono)
methyl)benzylidene)-4-oxo-2-thioxothiazolidin-3-yl)-4-
methylpentanoic acid (IIk)
Yield 80 %; m.p. 288–290 °C. IR (KBr) cm-1: 3318 (OH),
1689 (C=O).1H NMR (DMSO-d6, 300 MHz, ppm): d 0.92
(d, J = 9.0 Hz, 3H, CH3), 0.97 (d, J = 9.0 Hz, 3H, CH3),
1.54 (m, 1H, CH), 2.07–2.25 (m, 2H, CH2), 5.64 (m, 1H,
CH), 7.80–7.95 (m, 9H, Ar–H), 8.55 (s, 1H, N=CH), 12.14
(s, 1H, NH), 13.41 (s, 1H, COOH). MS (EI) m/z calcd for
C24H22BrN3O4S2 (M?) 561.02, found 562 (MH?).
(S)-2-((Z)-5-(4-((E)-(2-(2,3-Dimethoxybenzoyl)hydrazono)
methyl)benzylidene)-4-oxo-2-thioxothiazolidin-3-yl)-3-
phenylpropanoic acid (Ip)
(R)-4-methyl-2-((Z)-5-(4-((E)-(2-(4-Methylbenzoyl)
hydrazono)methyl)benzylidene)-4-oxo-2-thioxothiazolidin-
3-yl)pentanoic acid (IIo)
Yield 82 %; m.p. 186–188 °C. IR (KBr) cm-1: 3317 (OH),
1711 (C=O). 1H NMR (DMSO-d6, 300 MHz, ppm): d 3.52
(d, J = 9.0 Hz, 2H, CH2), 3.78 (s, 3H, CH3), 3.85 (s, 3H,
CH3), 5.88 (s, 1H, CH), 7.07–7.86 (m, 12H, Ar–H), 7.84 (s,
1H, Ph=CH), 8.32 (s, 1H, N=CH), 11.78 (s, 1H, NH), 13.46
(s, 1H, COOH). 13C NMR (DMSO-d6, 75 MHz, ppm): d
192.69, 168.68, 166.45, 162.24, 152.54, 146.22, 146.02,
136.66, 136.48, 133.84, 133.03, 131.33, 129.68, 128.98,
128.29, 127.90, 127.34, 126.75, 124.30, 120.27, 114.98,
61.19, 58.18, 56.03, 18.59. MS (EI) m/z calcd for
C29H25BrN3O6S2 (M?) 575.12, found 576 (MH?).
Yield 90 %; m.p. 232–234 °C. IR (KBr) cm-1: 3460 (OH),
1712 (C=O). 1H NMR (DMSO-d6, 300 MHz, ppm): d 0.92
(d, J = 9.0 Hz, 3H, CH3), 0.97 (d, J = 9.0 Hz, 3H, CH3),
1.54 (m, 1H, CH), 2.07–2.26 (m, 2H, CH2), 2.44 (s, 3H,
CH3), 5.65 (m, 1H, CH), 7.38–7.96 (m, 9H, Ar–H), 8.55 (s,
1H, N=CH), 12.00 (s, 1H, NH), 12.92 (s, 1H, COOH). 13C
NMR (DMSO-d6, 75 MHz, ppm): d 193.35, 169.31,
166.54, 163.03, 146.15, 141.97, 136.77, 133.89, 133.14,
131.26, 128.99, 127.83, 127.71, 121.52, 55.92, 24.82,
22.83, 21.93, 21.04. MS (EI) m/z calcd for C25H25N3O4S2
(M?) 515.07, found 516 (MH?).
(R)-2-((Z)-5-(4-((E)-(2-(4-Chlorobenzoyl)hydrazono)
methyl)benzylidene)-4-oxo-2-thioxothiazolidin-3-yl)-4-
methylpentanoic acid (IIc)
Yield 81 %; m.p. 254–256 °C. IR (KBr) cm-1: 3294 (OH),
1724 (C=O). 1H NMR (DMSO-d6, 300 MHz, ppm): d 0.92
(d, J = 9.0 Hz, 3H, CH3), 0.97 (d, J = 9.0 Hz, 3H, CH3),
1.54 (m, 1H, CH), 2.02–2.30 (m, 2H, CH2), 5.65 (m, 1H,
CH), 7.66–8.02 (m, 9H, Ar–H), 8.54 (s, 1H, N=CH), 12.14
(s, 1H, NH), 13.43 (s, 1H, COOH). 13C NMR (DMSO-d6,
75 MHz, ppm): d 193.91, 169.83, 167.02, 162.62, 147.21,
(2R)-2-((Z)-5-(4-((E)-(2-(4-Chlorobenzoyl)hydrazono)
methyl)benzylidene)-4-oxo-2-thioxothiazolidin-3-yl)-3-
methylpentanoic acid (IIIc)
Yield 79 %; m.p. 256–258 °C. IR (KBr) cm-1: 3466
(OH), 1707 (C=O). 1H NMR (DMSO-d6, 300 MHz,
ppm): d 0.81 (t, J = 7.5 Hz, 3H, CH3), 0.96–1.22 (m, 2H,
123

W. Li et al.
2-((Z)-5-(4-((E)-(2-(4-Chlorobenzoyl)hydrazono)
CH2), 1.17 (d, J = 6.0 Hz, 2H, CH3), 1.29 (m, 1H, CH),
5.24 (d, J = 9.0 Hz, 1H, CH), 7.66–8.02 (m, 9H, Ar–H),
8.50 (s, 1H, N=CH), 12.14 (s, 1H, NH), 13.29 (s, 1H,
COOH). 13C NMR (DMSO-d6, 75 MHz, ppm): d 193.76,
169.08, 167.12, 162.61, 147.19, 137.24, 137.09,
134.48, 133.95, 132.34, 131.82, 130.09, 129.07, 128.42,
121.74, 62.06, 33.56, 25.36, 18.04, 11.38. MS (EI)
m/z calcd for C24H22ClN3O4S2 (M?) 515.07, found 516
(MH?).
methyl)benzylidene)-4-oxo-2-thioxothiazolidin-3-yl)acetic
acid (IVc)
Yield 90 %; m.p. 223–225 °C. IR (KBr) cm-1: 3418 (OH),
1698 (C=O). 1H NMR (DMSO-d6, 300 MHz, ppm): d 4.81
(s, 2H, CH2), 7.68–8.01 (m, 9H, Ar–H), 8.54 (s, 1H,
N=CH), 12.13 (s, 1H, NH), 13.42 (s, 1H, COOH). MS (EI)
m/z calcd for C20H14ClN3O4S2 (M?) 459.01, found 460
(MH?).
(2R)-2-((Z)-5-(4-((E)-(2-(1-Naphthoyl)hydrazono)methyl)
benzylidene)-4-oxo-2-thioxothiazolidin-3-yl)-3-
methylpentanoic acid (IIId)
2-((Z)-5-(4-((E)-(2-(1-Naphthoyl)hydrazono)methyl)
benzylidene)-4-oxo-2-thioxothiazolidin-3-yl)acetic acid
(IVd)
Yield 82 %; m.p. 278–280 °C. IR (KBr) cm-1: 3429 (OH),
1694 (C=O). 1H NMR (DMSO-d6, 300 MHz, ppm): d 0.86
(t, J = 7.5 Hz, 3H, CH3), 0.97–1.09 (m, 2H, CH2), 1.22 (d,
J = 6.0 Hz,2H, CH3), 1.30 (m, 1H, CH), 5.30 (d,
J = 9.0 Hz, 1H, CH), 7.65–8.29 (m, 12H, Ar–H), 8.44 (s,
1H, N=CH), 12.24 (s, 1H, NH), 13.27 (s, 1H, COOH). MS
(EI) m/z calcd for C28H25N3O4S2 (M?) 531.13, found 532
(MH?).
Yield 90 %; m.p. 261–264 °C. IR (KBr) cm-1: 3418 (OH),
1697 (C=O). 1H NMR (DMSO-d6, 300 MHz, ppm): d 4.81
(s, 2H, CH2), 7.44–8.29 (m, 12H, Ar–H), 8.44 (s, 1H,
N=CH), 12.23 (s, 1H, NH), 13.47 (s, 1H, COOH). MS (EI)
m/z calcd for C24H17N3O4S2 (M?) 475.07, found 476
(MH?).
2-((Z)-5-(4-((E)-(2-(4-Bromobenzoyl)hydrazono)
methyl)benzylidene)-4-oxo-2-thioxothiazolidin-3-yl)acetic
acid (IVk)
(2R)-2-((Z)-5-(4-((E)-(2-(4-Bromobenzoyl)hydrazono)
methyl)benzylidene)-4-oxo-2-thioxothiazolidin-3-yl)-3-
methylpentanoic acid (IIIk)
Yield 85 %; m.p. 257–259 °C. IR (KBr) cm-1: 3418 (OH),
1698 (C=O). 1H NMR (DMSO-d6, 300 MHz, ppm): d 4.80
(s, 2H, CH2), 7.80–7.97 (m, 9H, Ar–H), 8.54 (s, 1H,
N=CH), 12.13 (s, 1H, NH), 13.52 (s, 1H, COOH). MS (EI)
m/z calcd for C20H14BrN3O4S2 (M?) 504.96, found 506
(MH?).
Yield 73 %; m.p. 266–267 °C. IR (KBr) cm-1: 3421 (OH),
1702 (C=O). 1H NMR (DMSO-d6, 300 MHz, ppm): d 0.81
(t, J = 7.5 Hz, 3H, CH3), 0.96–1.08 (m, 2H, CH2), 1.17 (d,
J = 6.0 Hz, 2H, CH3), 1.24 (m, 1H, CH), 5.24 (d,
J = 9.0 Hz, 1H, CH), 7.76–7.79 (m, 9H, Ar–H), 8.50 (s,
1H, N=CH), 12.09 (s, 1H, NH), 13.21 (s, 1H, COOH). MS
(EI) m/z calcd for C24H22BrN3O4S2 (M?) 561.02, found
562 (MH?).
2-((Z)-5-(4-((E)-(2-(4-Chlorobenzoyl)hydrazono)
methyl)benzylidene)-4-oxo-2-thioxothiazolidin-3-yl)acetic
acid (IVo)
Yield 92 %; m.p. 199–201 °C. IR (KBr) cm-1: 3421 (OH),
1696 (C=O). 1H NMR (DMSO-d6, 300 MHz, ppm): d 4.79
(s, 2H, CH2), 7.37–7.95 (m, 9H, Ar–H), 8.53 (s, 1H,
N=CH), 12.01 (s, 1H, NH). MS (EI) m/z calcd for
C21H17N3O4S2 (M?) 439.07, found 440 (MH?).
(2R)-3-Methyl-2-((Z)-5-(4-((E)-(2-(4-methylbenzoyl)
hydrazono)methyl)benzylidene)-4-oxo-2-thioxothiazolidin-
3-yl)pentanoic acid (IIIo)
Yield 88 %; m.p. 186–188 °C. IR (KBr) cm-1: 3427
(OH), 1701 (C=O). 1H NMR (DMSO-d6, 300 MHz,
ppm): d 0.81 (t, J = 7.5 Hz, 3H, CH3), 0.96–1.05 (m, 2H,
CH2), 1.17 (d, J = 6.0 Hz, 2H, CH3), 1.24 (m, 1H, CH),
2.39 (s, 3H, CH3), 5.24 (d, J = 9.0 Hz, 1H, CH),
7.33–7.89 (m, 9H, Ar–H), 8.50 (s, 1H, N=CH), 11.95 (s,
1H, NH), 13.18 (s, 1H, COOH). 13C NMR (DMSO-d6,
75 MHz, ppm): d 193.53, 168.59, 166.67, 162.97, 146.15,
142.02, 136.85, 133.86, 133.50, 131.33, 130.35, 129.01,
127.84, 127.74, 121.19, 61.61, 33.09, 24.90, 21.04, 17.55,
10.88. MS (EI) m/z calcd for C25H25N3O4S2 (M?) 515.07,
found 516 (MH?).
(R)-2-((Z)-5-(4-((E)-(2-(4-Chlorobenzoyl)hydrazono)
methyl)benzylidene)-4-oxo-2-thioxothiazolidin-3-yl)-3-
(1H-indol-2-yl)propanoic acid (Vc)
Yield 89 %; m.p. 278–280 °C. IR (KBr) cm-1: 3428 (OH),
1705 (C=O). 1H NMR (DMSO-d6, 300 MHz, ppm): d
3.64–3.76 (m, 2H, CH2), 5.93 (m, 1H, CH), 6.93–8.02 (m,
14H, Ar–H), 8.53 (s, 1H, N=CH), 10.85 (s, 1H, NH), 12.12
(s, 1H, NNH), 13.45 (s, 1H, COOH). MS (EI) m/z calcd for
C29H21ClN4O4S2 (M?) 588.07, found 589 (MH?).
123

Novel arylhydrazone derivatives bearing a rhodanine moiety
(R)-2-((Z)-5-(4-((E)-(2-(1-Naphthoyl)hydrazono)
methyl)benzylidene)-4-oxo-2-thioxothiazolidin-3-yl)-3-
(1H-indol-2-yl)propanoic acid (Vd)
of 64–1 lg/mL. The MIC value was defined as the con-
centration of test compound required to completely inhibit
the growth of the bacteria during a 24 h incubation period
at 37 °C. The growth of the bacteria was determined by
measuring the absorption at 650 nm using a microtiter
enzyme-linked immunosorbent assay (ELISA) reader. All
of the experiments were conducted in triplicate.
Yield 90 %; m.p. 281–283 °C. IR (KBr) cm-1: 3432 (OH),
1706 (C=O). 1H NMR (DMSO-d6, 300 MHz, ppm): d
3.66–3.77 (m, 2H, CH2), 5.89 (m, 1H, CH), 6.96–8.26 (m,
17H, Ar–H), 8.43 (s, 1H, N=CH), 10.84 (s, 1H, NH), 12.23
(s, 1H, NNH). MS (EI) m/z calcd for C33H24N4O4S2 (M?)
604.12, found 605 (MH?).
Evaluation of cytotoxicity
Human cervical (HeLa) cell monolayers were used as an
in vitro model of the cervico-vaginal epithelium for testing
the cytotoxicities of the new compounds. HeLa cells were
grown in Dulbecco modified Eagle medium (DMEM) sup-
plemented with fetal bovine serum (10 %), and antibiotics
(penicillin–streptomycin mixture [100 U/ml]). Cells at
80–90 % confluence were split by trypsin (0.25 % in phos-
phate buffered saline (PBS); pH 7.4), and the medium was
changed at 24 h intervals. The cells were cultured at 37 °C in
a 5 % CO2 incubator. The cells were grown for three pas-
sages and *1 9 104 cells were seeded into each well of a
96-well plate and incubated overnight to allow the cells to
become attached to the substrate. After 24 h, the medium
was replaced with DMEM supplemented with 10 % FBS
containing a variety of different concentrations of the test
compounds and incubated for 48 h. A 10 lL portion of an
MTT solution (5 mg/mL in PBS) was then added to each
well. Following a 4 h period of incubation, the medium was
removed and the resulting formazan crystals were dissolved
with in DMSO (100 lL). Following a period of shaking for
10 min, the optical density was measured at 570 nm using a
microtiter ELISA reader. The assay was conducted four
times. The IC50 values were defined as the concentrations
inhibiting the cell growth by 50 %.
(R)-2-((Z)-5-(4-((E)-(2-(4-Bromobenzoyl)hydrazono)
methyl)benzylidene)-4-oxo-2-thioxothiazolidin-3-yl)-3-
(1H-indol-2-yl)propanoic acid (Vk)
Yield 81 %; m.p. 283–285 °C. IR (KBr) cm-1: 3432 (OH),
1706 (C=O). 1H NMR (DMSO-d6, 300 MHz, ppm): d
3.36–3.75 (m, 2H, CH2), 5.93 (m, 1H, CH), 6.93–7.94 (m,
14H, Ar–H), 8.55 (s, 1H, N=CH), 10.84 (s, 1H, NH), 12.14
(s, 1H, NNH), 13.41 (s, 1H, COOH). MS (EI) m/z calcd for
C29H21BrN4O4S2 (M?) 632.02, found 633 (MH?).
(R)-3-(1H-Indol-2-yl)-2-((Z)-5-(4-((E)-(2-(4-
Methylbenzoyl)hydrazono)methyl)benzylidene)-4-oxo-2-
thioxothiazolidin-3-yl)propanoic acid (Vo)
Yield 83 %; m.p. 241–243 °C. IR (KBr) cm-1: 3427 (OH),
1701 (C=O). 1H NMR (DMSO-d6, 300 MHz, ppm): d 2.43
(s, 3H, CH3), 3.38–3.81 (m, 2H, CH2), 5.94 (m, 1H, CH),
6.93–7.90 (m, 14H, Ar–H), 8.53 (s, 1H, N=CH), 10.84 (s,
1H, NH), 11.99 (s, 1H, NNH), 13.45 (s, 1H, COOH). MS
(EI) m/z calcd for C30H24N4O4S2 (M?) 568.12, found 569
(MH?).
In vitro evaluation of the antibacterial activity
of the compounds
The anti-bacterial activities of the compounds were eval-
uated in vitro in 96-well microtiter plates. A serial dilution
method was used to obtain the minimum inhibitory con-
centration (MIC) values of the synthesized compounds
against several different bacterial strains, including multi-
drug-resistant clinical isolates. Oxacillin and norfloxacin
were used as positive controls. The test bacteria were
grown to the mid-log phase in Mueller–Hinton broth
(MHB) and subsequently diluted 1,000-fold in the same
medium. The bacteria of 105 CFU/mL were inoculated
into MHB and dispensed at 0.2 mL/well in a 96-well
microtiter plate. Oxacillin and norfloxacin were used as
positive controls. The test compounds were prepared in
dimethyl sulfoxide (DMSO), with the final concentrations
of the compounds not exceeding 0.05 %. A 2-fold serial
dilution technique was used to obtain final concentrations
Result and discussion
Anti-microbial activity
Compounds I–V were evaluated for their antibacterial
activities against three strains of Gram-positive bacteria (S.
aureus RN4220, S. aureus KCTC 503 and S. aureus KCTC
209), four strains of multidrug-resistant Gram-positive
bacteria (Methicillin-resistant S. aureus (MRSA CCARM
3167 and MRSA CCARM 3506), Quinolone-resistant S.
aureus (QRSA CCARM 3505 and QRSA CCARM 3519))
and one strain of Gram-negative bacteria (Escherichia coli
CCARM 1356) using a conventional agar-dilution method.
The MIC values of the compounds were subsequently
determined and compared with those of oxacillin and
norfloxacin, which were used as reference inhibitors.
123

W. Li et al.
For series I, derivatives that contained a heterocyclic
aromatic ring (Ar groups) did not exhibit any activity
against the bacterial strains tested, indicating that the
phenyl ring was critical for the activity. Based on these
results, the corresponding derivatives were not considered
for synthesis in any of the other series.
Table 1 Inhibitory activity of compounds I–V expressed as MIC
(lg/mL) (lM)
Compound Ar
S.aureus
E.coli
4220a
503b
209c
1356d
Ia
Ib
Ic
Id
Ie
If
Furan-2-yl
[64
[64
[64
[64
C6H5
32 (62) [64
64 (124) [64
16 (29) [64
A preliminary in vitro assay revealed that most of the
derivatives did not show any anti-bacterial activity
against the Gram-negative strain (E. coli CCARM 1356) at
64 lg/mL, whereas most of the derivatives exhibited
potent antibacterial activities against the Gram-positive
strains. Of the compounds tested, compounds from series II
and III showed excellent levels of inhibition against the
three Gram-positive strains (S. aureus RN 4220, S. aureus
KCTC 209 and S. aureus KCTC 503) with MIC values in
the range of 2–8 lg/mL. Compounds IId, IIk, IIId and
IIIk (MIC = 2 lg/mL) were all 2-fold more potent than
the positive control norfloxacin (MIC = 4 lg/mL) against
the S. aureus KCTC 209, but were also 2- to 4-fold less
potent against S. aureus RN 4220 and S. aureus KCTC 503,
and showed lower levels of potency than the positive
control oxacillin (MIC = 1 lg/mL) against the three
Gram-positive strains (Table 1).
C6H4(4-Cl)
Naphthalen-1-yl
C6H4(3-Cl)
C6H4(2-Cl)
C6H4(3-NO2)
Pyridin-3-yl
C6H4(2-CH3)
C6H4(3-CH3)
C6H4(4-Br)
C6H4(3-Br)
C6H4(4-OCH3)
Pyridin-4yl
C6H4(4-CH3)
4 (7)
8 (14)
8 (14)
8 (14)
16 (29)
16 (29)
8 (14)
8 (14)
[64
[64
64 (117) 64 (117) 64 (117) [64
Ig
Ih
Ii
32 (57)
[64
32 (57)
[64
32 (57) [64
[64 [64
32 (60)
32 (60)
16 (27)
16 (27)
16 (29)
[64
32 (60)
16 (30)
8 (13)
32 (60) [64
32 (60) [64
Ij
Ik
Il
4 (7)
[64
16 (27)
16 (29)
16 (27) [64
16 (29) [64
Im
In
Io
Ip
64 (124) [64
8 (15) 8 (15)
[64
[64
32 (60)
C6H3(2,3-
(OCH3)2)
64 (111) 32 (56)
64 (111) [64
IIc
C6H4(4-Cl)
8 (16)
8 (15)
4 (7)
8 (16)
4 (8)
4 (7)
8 (16)
8 (16)
4 (8)
4 (7)
4 (8)
[64
8 (16)
2 (4)
2 (4)
4 (8)
4 (8)
2 (4)
2 (4)
4 (8)
[64
[64
[64
[64
[64
[64
[64
[64
[64
[64
[64
[64
[64
[64
[64
[64
IId
Naphthalen-1-yl
C6H4(4-Br)
IIk
All of the newly synthesized compounds were also
tested for their inhibitory activities against the clinical
isolates of several different multidrug-resistant Gram-
positive bacterial strains, including Methicillin-resistant S.
aureus (MRSA CCARM 3167 and MRSA CCARM 3506)
and Quinolone-resistant S. aureus (QRSA CCARM 3505
and QRSA CCARM 3519), as shown in Table 2. The results
revealed that the newly synthesized compounds provided
similar levels of inhibitory activity in both the conventional
and multidrug-resistant bacterial strains. Compounds from
series II and III exhibited higher levels of inhibitory
activity against the different multidrug-resistant Gram-
positive bacterial strains, with compounds IIk and IIIk in
particular showing excellent levels of inhibitory activity
against MRSA CCARM 3167 and 3506 with an MIC value
of 4 lg/mL. This value represented a 2-fold increase in
potency relative to the standard drug norfloxacin and a
16-fold increase relative to oxacillin (MIC [ 64 lg/mL).
For the QRSA CCARM 3505 and 3519 strains, although
these compounds exhibited lower levels of inhibitory
activity with an MIC value of 4 lg/mL (oxacillin,
MIC = 1 lg/mL), they showed much higher levels of
activity than norfloxacin (MIC [ 64 lg/mL).
IIo
C6H4(4-CH3)
C6H4(4-Cl)
8 (16)
8 (16)
8 (15)
4 (7)
IIIc
IIId
IIIk
IIIo
IVc
Naphthalen-1-yl
C6H4(4-Br)
C6H4(4-CH3)
C6H4(4-Cl)
8 (16)
[64
IVd
IVk
IVo
Vc
Naphthalen-1-yl
C6H4(4-Br)
[64
[64
[64
[64
C6H4(4-CH3)
C6H4(4-Cl)
[64
[64
64 (109) 64 (109) 32 (54) [64
64 (106) 64 (106) 64 (106) [64
64 (101) 64 (101) 64 (101) [64
64 (113) 64 (113) 64 (113) [64
Vd
Naphthalen-1-yl
C6H4(4-Br)
Vk
Vo
C6H4(4-CH3)
Oxacillin
Norfloxacin
1 (2)
2 (6)
1 (2)
2 (6)
1 (2)
[64
4 (13)
16 (50)
Numbers in parentheses represent the MIC converted to molar concentrations
(lM)
a
Staphylococcus aureus RN4220
b
Staphylococcus aureus 503
c
Staphylococcus aureus 209
d
Escherichia coli CCARM 1356
Among the tested compounds in the five series, the
compounds in series II and III showed excellent inhibition
against the seven Gram-positive Strains (including drug-
resistance bacteria), with MIC values in the range of
2–16 lg/mL. Compounds in series I displayed moderate to
good inhibition against the seven Gram-positive Strains.
However, the activity of compounds in series IV and V was
low. The compounds from series V were less active than
those from the other four series of compounds.The mech-
anism of action of the compounds tested in this study will
be done in the next study.
No clear correlations were found for any of these
compounds in terms of their anti-bacterial activity and the
123

Novel arylhydrazone derivatives bearing a rhodanine moiety
Table 2 Inhibitory activity (MIC, lg/mL) (lm) of compounds
I–V against clinical isolates of multidrug-resistant Gram-positive strains
Table 3 Cytotoxic activity of compounds IIk and IIIk against HeLa
cell
Compound Ar
MRSA
3167a
QRSA
3505c
Compound
MIC(lg/mL)
ICa50 (lg/mL)
3506b
3519d
IIk
IIIk
a
2 or 4
2 or 4
18.62
9.01
Ia
Ib
Ic
Id
Ie
If
Furan-2-yl
[64
[64
[64
[64
C6H5
32 (62)
16 (29)
8 (14)
8 (15)
16 (29)
32 (57)
[64
64 (116) 32 (62)
32 (62)
8 (15)
16 (28)
16 (29)
32 (58)
32 (57)
[64
IC50 is the concentrations required to inhibit 50 % of cell growth
C6H4(4-Cl)
Naphthalen-1-yl
C6H4(3-Cl)
C6H4(2-Cl)
C6H4(3-NO2)
Pyridin-3-yl
C6H4(2-CH3)
C6H4(3-CH3)
C6H4(4-Br)
C6H4(3-Br)
C6H4(4-OCH3)
Pyridin-4yl
C6H4(4-CH3)
8 (15)
16 (28)
16 (29)
32 (58)
32 (57)
[64
8 (15)
8 (14)
16 (29)
32 (58)
32 (57)
[64
and IIIk did not affect the cell viability of Human cervical
(HeLa) cells at their MICs (4 and 2 lg/mL, respectively)
but showed cytotoxicity at much higher concentrations
(IC50 = 18.62 or 9.01 lg/mL, respectively). The differ-
ences between the antibacterial and cytotoxic activities of
these two compounds suggested that compounds IIk and
IIIk exhibited in vitro antibacterial activities at non-cyto-
toxic concentrations.
Ig
Ih
Ii
32 (60)
8 (15)
16 (27)
8 (13)
16 (29)
[64
32 (60)
8 (15)
8 (13)
16 (27)
32 (59)
[64
32 (60)
8 (15)
8 (13)
8 (13)
16 (29)
[64
32 (60)
8 (15)
4 (7)
Ij
Ik
Il
8 (13)
16 (29)
[64
Im
In
Io
Ip
8 (15)
32 (56)
8 (15)
32 (56)
8 (15)
32 (56)
8 (15)
32 (56)
C6H3(2,3-
(OCH3)2)
Conclusion
IIc
C6H4(4-Cl)
4 (8)
2 (4)
4 (7)
8 (16)
4 (8)
4 (8)
4 (7)
4 (8)
[64
[64
[64
[64
8 (16)
4 (8)
4 (7)
8 (16)
8 (16)
4 (8)
4 (7)
8 (16)
[64
8 (16)
8 (15)
4 (7)
8 (16)
4 (8)
8 (16)
4 (7)
8 (16)
[64
16 (31)
4 (8)
4 (7)
8 (16)
8 (16)
8 (16)
4 (7)
4 (8)
[64
IId
Naphthalen-1-yl
C6H4(4-Br)
In the present study, a series of arylhydrazone derivatives
bearing a rhodanine moiety were synthesized and their
antimicrobial activities evaluated against a variety of
Gram-positive and Gram-negative bacteria. Some of the
synthesized compounds showed potent anti-bacterial
activities against Gram-positive bacteria, particularly
against the multidrug-resistant strains of clinical isolates.
Compound IIk and IIIk were found to possess the most
potent inhibitory activities of the compounds synthesized
in the current study. These results suggested that the
introduction of an arylhydrazone moiety to the 5-benzy-
lidenethiazolidine-2,4-dione scaffold would not lead to a
reduction in the antibacterial activity of these compounds,
and the further development of such compounds could be
of significant interest, especially in relation to the search
for new derivatives against Methicillin-resistant S. aureus
and Quinolone-resistant S. aureus.
IIk
IIo
C6H4(4-CH3)
C6H4(4-Cl)
IIIc
IIId
IIIk
IIIo
IVc
Naphthalen-1-yl
C6H4(4-Br)
C6H4(4-CH3)
C6H4(4-Cl)
IVd
IVk
IVo
Vc
Naphthalen-1-yl
C6H4(4-Br)
[64
[64
[64
[64
[64
[64
C6H4(4-CH3)
C6H4(4-Cl)
[64
[64
[64
64 (102) 32 (51)
64 (102) 16 (26)
64 (106) 64 (106) 32 (53)
64 (101) 32 (51) 64 (101)
64 (113) 64 (113) 32 (56)
Vd
Naphthalen-1-yl
C6H4(4-Br)
32 (53)
32 (51)
32 (56)
[64
Vk
Vo
C6H4(4-CH3)
Oxacillin
Norfloxacin
[64
1 (2)
1 (2)
8 (25)
4 (13)
[64
[64
Numbers in parentheses represent the MIC converted to molar concentrations
(lM)
a
Methicillin-resistant S. aureus CCARM 3167
Acknowledgments This study was supported by the National Sci-
ence Foundation of China (20962021).
b
Methicillin-resistant S. aureus CCARM 3506
c
Quinolone-resistant S. aureus CCARM 3505
d
Quinolone-resistant S. aureus CCARM 3519
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123