Thiazole-based aminopyrimidines and N-phenylpyrazolines as potent antimicrobial agents: Synthesis and biological evaluation

Article abstract of DOI:10.1039/c4md00124a

A series of eight thiazole-based N-phenylpyrazolines and two aminopyrimidines having several chalcone derivatives as precursors have been synthesized and evaluated for their antimicrobial activity. All compounds showed antimicrobial activity. The best activity was achieved for compounds 3a and 3b, while compounds 4d and 4g showed the lowest antimicrobial potential.

Full text of DOI:10.1039/c4md00124a

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CONCISE ARTICLE
Thiazole-based aminopyrimidines and
N-phenylpyrazolines as potent antimicrobial
agents: synthesis and biological evaluation
Cite this: Med. Chem. Commun., 2014,
5, 915
a
a
Konstantinos Liaras, Athina Geronikaki, Jasmina Glamoclija,b Ana C´iricb
*
ˇ
´
and Marina Sokovicb
´
Received 17th March 2014
Accepted 15th April 2014
A series of eight thiazole-based N-phenylpyrazolines and two aminopyrimidines having several chalcone
derivatives as precursors have been synthesized and evaluated for their antimicrobial activity. All
compounds showed antimicrobial activity. The best activity was achieved for compounds 3a and 3b,
while compounds 4d and 4g showed the lowest antimicrobial potential.
DOI: 10.1039/c4md00124a
www.rsc.org/medchemcomm
1. Introduction
Despite the success to date in the development of antimicrobial
agents, the inexorable, ongoing emergence of resistance
worldwide continues to spur the search for novel compounds to
replace or supplement conventional antibiotics and antifun-
gals.1–6 In addition, the need for effective antimicrobial drugs
became even greater considering the difficulties of dealing with
the treatment of infections of hospitalized patients and
protection of immunosuppressed and HIV-infected patients.7,8
Thus, the challenge of developing new categories of anti-
microbial agents reignited the interest of the scientists during
the last few decades. A potential approach is the design of
innovative drugs, with different mechanisms of action, in an
attempt to avoid cross-resistance to existing therapeuticals (e.g.
linezolid).9–11
N-Phenylpyrazolines and aminopyrimidines display a broad
spectrum of potential pharmacological activities such as anti-
microbial,12–15 anti-inammatory,16,17 antileishmanial,18,19 anti-
depressant,20 etc.
Fig. 1 Synthesized compounds.
Taking also into account our promising ndings regarding
the antibacterial and antifungal activities of thiazole deriva-
tives,21–25 a series of ten structurally new compounds incorpo-
rating thiazole and the above mentioned aza-heterocyclic
moieties were designed and synthesized.
2. Results and discussion
2.1. Chemistry
Eight thiazole-based N-phenylpyrazolines and two amino-
pyrimidines (Fig. 1) were synthesized having several chalcone
derivatives as precursors. The title compounds were tested for
their in vitro antimicrobial properties against Gram positive and
Gram negative bacteria and also a series of fungi.
The synthesis of the target N-phenylpyrazolines and amino-
pyrimidines was accomplished by heterocyclization of corre-
sponding chalcones with phenylhydrazine hydrochloride and
guanidine hydrochloride in the presence of NaOH respectively
(Scheme 1). The reactions proceed smoothly and in good yields
for the majority of the compounds.
Structures of synthesized compounds 3a,b and 4a–h were
satisfactorily conrmed by IR, 1H NMR and elemental analysis.
In IR spectra were observed absorptions at 1592–1596 cmꢀ1
(C]C arom.), 1638–1644 cmꢀ1 (C]N) and sharp bands at
aAristotle University, School of Pharmacy, Thessaloniki, 54124, Greece. E-mail:
geronik@pharm.auth.gr; Fax: +30 2310 998559; Tel: +30 2310 997616
b
´
Institute for biological research “S.Stankovic”, Mycological laboratory, University of
Belgrade, 11000, Serbia
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Scheme 1 Synthesis of title compounds.
3156–3164 (NH). As far as the aminopyrimidine derivatives are increasing public health threat. No new broad spectrum anti-
concerned, the characteristic band of primary amine (NH2) was biotics have been developed recently for most Gram negative
observed at 3311–3384 cmꢀ1. In the 1H NMR spectra, chemical bacteria.27 Moulds have various health effects. Excessive mould
shis of the nal compounds appeared in the region of d 2.35– growth in the human environment needs to be taken care of,
2.88 (thiazole 4-CH3), 3.04–3.26 (NCH3), 3.09–3.73 (CHAHBC] regardless of the species, as it may lead to an increased number
N, compounds 4a–h), and 3.82–4.06 (CHAHBC]N, compounds of allergy cases, toxicity, and house/building structural prob-
4a–h).
lems. Some Aspergillus, Penicillium, Trichoderma, Fusarium,
Alternaria species are able to produce mycotoxins that are
potent hepatocarcinogens in animals and humans. Therefore,
the presence of toxigenic fungi in foods, grains, and the envi-
ronment presents a potential hazard to human and animal
health.28 Minimum inhibitory concentrations (MICs) that
inhibited the growth of the tested microorganisms as well as the
minimum bactericidal/fungicidal concentration were deter-
mined. The results of antimicrobial testing against a panel of
selected Gram positive and Gram negative bacteria are reported
in Table 1, along with those of reference drugs ampicillin and
streptomycin.22
Almost all tested compounds were potent against all the
used bacteria with minimum inhibitory concentrations (MICs)
in the range of 1.45–44.16 ꢁ 10ꢀ2 mmol mlꢀ1 and minimum
bactericidal concentrations (MBCs) at 5.80–95.5 ꢁ 10ꢀ2 mmol
mlꢀ1. All tested compounds showed inhibitory activity at
concentrations in the range of 1.45–27.6 ꢁ 10ꢀ2 mmol mlꢀ1
towards Gram (+) bacteria, and 2.73–44.16 ꢁ 10ꢀ2 mmol mlꢀ1
towards Gram (ꢀ) bacteria. A bactericidal effect was achieved at
2.2. Biological evaluation
2.2.1. Antimicrobial activity. The synthesized thiazole-
based aminopyrimidines and N-phenylpyrazolines were assayed
in vitro for their antibacterial and antifungal activity against
Gram positive, Gram negative bacteria and molds obtained
from ATCC – American Type of Culture Collection. These
bacterial and fungal species are chosen because of their prop-
erties; among them are plant, animal and human pathogenic
species, also food spoilage and contaminators, and mycotoxin
producers could be found. More than 90 percent of the cases of
food poisoning each year are caused by Staphylococcus aureus,
Salmonella spp., Listeria monocytogenes, Bacillus cereus, and
entero-pathogenic Escherichia coli.26 Pseudomonas aeruginosa, as
an example, is an opportunistic human pathogen that infects
immunocompromised individuals and people with cystic
brosis. This bacterium has low sensitivity to antibiotic treat-
ment and has become multidrug resistant, which causes an
916 | Med. Chem. Commun., 2014, 5, 915–922
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Table 1 Antibacterial activity of title compounds towards Gram (+) bacteria (MIC and MBC in mmol mlꢀ1 ꢁ 10ꢀ2 ab
)
Compounds
S. a.
B. c.
M. f.
L. m.
3a
MIC
MBC
MIC
MBC
MIC
MBC
MIC
MBC
MIC
MBC
MIC
MBC
MIC
MBC
MIC
MBC
MIC
MBC
MIC
MBC
MIC
MBC
MIC
MBC
8.41 ꢂ 0.02b
3.37 ꢂ 0.02a
3.37 ꢂ 0.02a
10.10 ꢂ 0.10c
11.81 ꢂ 0.10a
1.45 ꢂ 0.00a
36.25 ꢂ 0.00b
5.70 ꢂ 0.10b
11.50 ꢂ 0.20a
5.52 ꢂ 0.07b
11.04 ꢂ 0.01a
7.60 ꢂ 0.10b
10.10 ꢂ 0.00a
9.60 ꢂ 0.10bc
11.04 ꢂ 0.00a
5.30 ꢂ 0.00a
10.60 ꢂ 0.20a
7.60 ꢂ 0.10b
10.20 ꢂ 0.07a
5.46 ꢂ 0.20b
95.50 ꢂ 0.20e
5.20 ꢂ 0.07a
10.50 ꢂ 0.20a
37.20 ꢂ 0.07e
74.40 ꢂ 0.10d
25.80 ꢂ 0.10d
51.60 ꢂ 0.20c
10.10 ꢂ 0.03b
1.45 ꢂ 0.00a
5.80 ꢂ 0.07a
11.50 ꢂ 0.07b
20.10 ꢂ 0.00c
2.76 ꢂ 0.01a
27.60 ꢂ 0.10d
12.6 ꢂ 0.20c
20.20 ꢂ 0.07d
11.04 ꢂ 0.00b
27.60 ꢂ 0.10d
10.60 ꢂ 0.20b
15.80 ꢂ 0.07bc
10.20 ꢂ 0.07b
20.30 ꢂ 0.03c
2.73 ꢂ 0.01a
27.30 ꢂ 0.00d
10.50 ꢂ 0.20bc
21.00 ꢂ 0.50c
24.80 ꢂ 0.07d
37.20 ꢂ 0.00e
17.20 ꢂ 0.07cd
34.40 ꢂ 0.10e
6.74 ꢂ 0.10a
5.80 ꢂ 0.10a
40.60 ꢂ 0.10d
23.00 ꢂ 0.70c
28.70 ꢂ 0.00bc
5.52 ꢂ 0.07a
27.60 ꢂ 0.10b
15.20 ꢂ 0.07b
30.4 ꢂ 0.10c
5.52 ꢂ 0.07a
27.60 ꢂ 0.10b
15.80 ꢂ 0.10b
26.40 ꢂ 0.10b
20.30 ꢂ 0.10c
25.40 ꢂ 0.10b
5.46 ꢂ 0.02a
27.30 ꢂ 0.10b
15.70 ꢂ 0.07b
31.40 ꢂ 0.10c
24.80 ꢂ 0.10c
37.20 ꢂ 0.07d
4.30 ꢂ 0.10a
8.60 ꢂ 0.00a
8.41 ꢂ 0.10a
5.80 ꢂ 0.10a
29.00 ꢂ 0.00d
11.50 ꢂ 0.00b
23.00 ꢂ 0.30c
11.04 ꢂ 0.01b
44.16 ꢂ 0.05f
12.60 ꢂ 0.02b
20.20 ꢂ 0.07c
27.60 ꢂ 0.10c
58.60 ꢂ 0.20g
10.60 ꢂ 0.20b
15.80 ꢂ 0.10b
12.70 ꢂ 0.10b
20.30 ꢂ 0.00c
5.46 ꢂ 0.00a
47.80 ꢂ 0.30f
10.50 ꢂ 0.02b
21.00 ꢂ 0.10cd
24.80 ꢂ 0.02c
37.20 ꢂ 0.07e
8.60 ꢂ 0.10 ab
17.20 ꢂ 0.00c
3b
4a
4b
4c
4d
4e
4f
4g
4h
Ampicillin
Streptomycin
a
S. a. – Staphylococcus aureus (ATCC 6538); B. c. – Bacillus cereus (clinical isolate); M. f. – Micrococcus avus (ATCC 10240); L. m. – Listeria
monocytogenes (NCTC 7973). b In each column, and for MIC or MBC values, different letters mean signicant differences between samples (p < 0.05).
5.80–95.5 ꢁ 10ꢀ2 mmol mlꢀ1 against Gram (+) bacteria and 6.74– (except 4g), as well as against P. aeruginosa, S. typhimurium and
58.6 ꢁ 10ꢀ2 mmol mlꢀ1 on Gram (ꢀ) bacteria but the majority of E. coli. Almost all compounds showed a higher antibacterial
tested compounds did not inuence E. facealis and E. cloacae, effect than ampicillin, with some exception (Tables 1 and 2).
which are also Gram (ꢀ) bacteria. So, it can be seen that tested
The SAR studies revealed that substitution both in thiazole
compounds were more potent against Gram (+) than Gram (ꢀ) as well as in the benzene ring played an important role in the
bacterial species. It should be mentioned that their activity was antibacterial activity of the tested compounds. Thus, it was
comparable to that of ampicillin with MICs at 24.8–74.4 ꢁ 10ꢀ2 observed that the replacement of the methylamino group in
mmol mlꢀ1 and bactericidal concentrations at 37.2–124.0 ꢁ compound 4a with the ethylamino group (4b) led to a decrease
10ꢀ2 mmol mlꢀ1
.
of antibacterial potential, while the introduction of the phenyl
Streptomycin showed MICs in the range of 4.3–25.8 ꢁ 10ꢀ2 ring had the opposite effect. Thus, the activity observed among
mmol mlꢀ1 and MBCs of 8.6–51.6 ꢁ 10ꢀ2 mmol mlꢀ1. However, it these three compounds followed the order 4c > 4a > 4b. In the
should be noticed that some compounds showed activity case of methylamino derivatives, the introduction of 4-OMe, 4-
against some bacterial species better than streptomycin.
Cl and 4-NO2 (4e, 4f and 4h) slightly increased the activity
Compound 3b exhibited the best inhibitory effect with inhib- compared to compound 4a, while the introduction of the 4-Me
itory activity at 1.45–5.8 ꢁ 10ꢀ2 mmol mlꢀ1 against Gram (+) or 4-F-substituent (4d and 4g) had the opposite effect.
bacteria. Compound 4g also exhibited very high inhibitory activity
The results of antifungal activity of compounds 3a,b, 4a–h
on all bacterial species, but the bactericidal effect was higher than tested by a microdilution method are presented in Tables 3 and 4.
that for other compounds especially against L. monocytogenes The minimum inhibitory concentration (MIC) is in the range of
where the MBC was 27.3–95.5 ꢁ 10ꢀ2 mmol mlꢀ1. In general 1.45–47.80 ꢁ 10ꢀ2 mmol mlꢀ1 and minimum fungicidal concen-
compound 3a showed the best antibacterial activity on both Gram tration (MFC) is in the range of 3.37–95.5 ꢁ 10ꢀ2 mmol mlꢀ1
.
(+) and Gram (ꢀ) bacterial species. The lowest antibacterial
The best antifungal potential was obtained for compound 3a
activity was observed for compound 4d with MICs at 5.50–44.1 ꢁ which exhibited the strongest antifungal activity with MICs of
10ꢀ2 mmol mlꢀ1 and MBCs at 11.04–58.6 ꢁ 10ꢀ2 mmol mlꢀ1, and 1.45–5.05 mmol ꢁ 10ꢀ2 mlꢀ1 and MFCs of 3.37–6.74 mmol ꢁ
this compound was inactive against En. cloacae bacteria.
10ꢀ2 mlꢀ1. This compound did not inuence A. versicolor, etc.
The most sensitive bacterial species on these compounds are Compound 4g showed the lowest antifungal activity with MICs
Listeria monocytogenes (with exception for compound 4g), while of 5.46–47.8 mmol ꢁ 10ꢀ2 mlꢀ1 and fungicidal potential MFCs
En. faecalis and En. cloacae are the more resistant species.
Thus, all the compounds showed a stronger antibacterial the best activity against A. ochraceus and A. versicolor, while A.
effect than streptomycin against S. aureus and L. monocytogenes niger and C. albicans were the most resistant species. It should
at 10.92–95.5 mmol ꢁ 10ꢀ2 mlꢀ1. All the compounds exhibited
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Table 2 Antibacterial activity of title compounds towards Gram (ꢀ) bacteria (MIC and MBC in mmol mlꢀ1 ꢁ 10ꢀ2 ab
)
Compounds
Ps. aer.
S. typh.
E. coli
En. f.
En. cl.
3a
MIC
MBC
MIC
MBC
MIC
MBC
MIC
MBC
MIC
MBC
MIC
MBC
MIC
MBC
MIC
MBC
MIC
MBC
MIC
MBC
MIC
MBC
MIC
MBC
3.37 ꢂ 0.02a
3.37 ꢂ 0.02a
6.74 ꢂ 0.02a
3.37 ꢂ 0.00a
6.74 ꢂ 0.00a
34.80 ꢂ 0.10d
40.60 ꢂ 0.20d
17.20 ꢂ 0.00c
20.10 ꢂ 0.03b
27.60 ꢂ 0.10cd
44.16 ꢂ 0.05d
10.10 ꢂ 0.07b
17.70 ꢂ 0.20b
27.60 ꢂ 0.10cd
58.60 ꢂ 0.20e
18.50 ꢂ 0.20c
21.10 ꢂ 0.00b
17.80 ꢂ 0.00c
20.30 ꢂ 0.10b
5.46 ꢂ 0.02a
47.80 ꢂ 0.00d
18.30 ꢂ 0.10c
21.00 ꢂ 0.30b
37.20 ꢂ 0.07d
49.20 ꢂ 0.07d
17.20 ꢂ 0.00c
34.40 ꢂ 0.10c
nt
nt
6.74 ꢂ 0.08a
8.41 ꢂ 0.10a
nt
6.74 ꢂ 0.08a
29.00 ꢂ 0.30d
40.60 ꢂ 0.00d
14.40 ꢂ 0.10b
45.90 ꢂ 0.10d
27.60 ꢂ 0.00d
44.16 ꢂ 0.05d
15.20 ꢂ 0.07b
25.30 ꢂ 0.10b
27.60 ꢂ 0.20d
33.12 ꢂ 0.04c
15.80 ꢂ 0.10b
26.40 ꢂ 0.10b
20.30 ꢂ 0.10cd
25.40 ꢂ 0.10b
2.73 ꢂ 0.01a
3b
29.00 ꢂ 0.00d
34.80 ꢂ 0.30d
17.20 ꢂ 0.07bc
28.70 ꢂ 0.02d
27.60 ꢂ 0.10d
30.90 ꢂ 0.20d
20.20 ꢂ 0.07c
25.30 ꢂ 0.10c
11.04 ꢂ 0.10b
27.60 ꢂ 0.20cd
18.50 ꢂ 0.20bc
26.40 ꢂ 0.00c
15.20 ꢂ 0.10b
25.40 ꢂ 0.10c
5.46 ꢂ 0.02a
29.00 ꢂ 0.07c
34.80 ꢂ 0.00c
nt
4a
nt
nt
14.40 ꢂ 0.10bc
20.10 ꢂ 0.00bc
nt
4b
11.04 ꢂ 0.10b
27.6 ꢂ 0.10b
nt
4c
nt
nt
12.60 ꢂ 0.20b
17.70 ꢂ 0.10b
nt
4d
44.16 ꢂ 0.05d
58.64 ꢂ 0.20d
nt
nt
4e
13.20 ꢂ 0.07b
18.50 ꢂ 0.20b
12.70 ꢂ 0.10b
20.30 ꢂ 0.10bc
nt
nt
nt
nt
4f
4g
5.46 ꢂ 0.20a
27.30 ꢂ 0.10b
nt
27.30 ꢂ 0.10b
15.20 ꢂ 0.07b
31.40 ꢂ 0.10c
74.40 ꢂ 0.10e
124.00 ꢂ 0.70e
17.20 ꢂ 0.00c
34.40 ꢂ 0.00cd
27.30 ꢂ 0.10cd
15.20 ꢂ 0.07b
18.30 ꢂ 0.10b
24.80 ꢂ 0.00c
49.20 ꢂ 0.07e
17.20 ꢂ 0.07bc
34.40 ꢂ 0.10d
nt
4h
13.10 ꢂ 0.10b
18.30 ꢂ 0.10b
24.80 ꢂ 0.20c
37.20 ꢂ 0.07c
4.30 ꢂ 0.01a
8.60 ꢂ 0.10a
nt
Ampicilin
Streptomycin
24.80 ꢂ 0.30c
37.20 ꢂ 0.07c
4.30 ꢂ 0.10a
8.60 ꢂ 0.10a
a
Ps. aer. – Pseudomonas aeruginosa (ATCC 27853); S. typh. – Salmonella typhimurium (ATCC 13311); E. coli – Escherichia coli (ATCC 35210);
b
En. f. – Enterococcus faecalis (human isolate); En. cl. – Enterobacter cloacae (human isolate). In each column, and for MIC or MBC values,
different letters mean signicant differences between samples (p < 0.05).
Table 3 Antifungal activity of title compounds (MIC and MFC in mmol mlꢀ1 ꢁ 10ꢀ2 a
)
Compounds
A. o.
A. ver.
A. .
A. n.
A. fum.
3a
MIC
MFC
MIC
MFC
MIC
MFC
MIC
MFC
MIC
MFC
MIC
MFC
MIC
MFC
MIC
MFC
MIC
MFC
MIC
MFC
MIC
MFC
MIC
MFC
3.37 ꢂ 0.10a
nt
nt
5.05 ꢂ 0.02a
5.05 ꢂ 0.02a
5.05 ꢂ 0.02a
6.74 ꢂ 0.20a
5.80 ꢂ 0.00a
34.80 ꢂ 0.30e
14.30 ꢂ 0.10b
23.00 ꢂ 0.00d
11.04 ꢂ 0.01b
44.16 ꢂ 0.05f
12.60 ꢂ 0.20b
15.20 ꢂ 0.07c
27.60 ꢂ 0.10c
44.16 ꢂ 0.05f
26.40 ꢂ 0.10c
37.00ꢂ 0.00e
12.70 ꢂ 0.20b
15.20 ꢂ 0.07c
5.46 ꢂ 0.20a
10.92 ꢂ 0.30b
13.10 ꢂ 0.03b
26.20 ꢂ 0.07c
38.00 ꢂ 0.00d
95.00 ꢂ 0.03h
48.00 ꢂ 0.00e
64.00 ꢂ 0.30g
6.74 ꢂ 0.10a
1.45 ꢂ 0.20a
5.80 ꢂ 0.30a
14.3 ꢂ 0.10c
17.2 ꢂ 0.07c
2.76 ꢂ 0.00a
11.04 ꢂ 0.10b
12.60 ꢂ 0.20c
20.20 ꢂ 0.07c
9.60 ꢂ 0.10b
11.04 ꢂ 0.00b
13.20 ꢂ 0.07c
13.20 ꢂ 0.07b
12.70 ꢂ 0.20c
20.30 ꢂ 0.10c
5.46 ꢂ 0.20ab
27.30 ꢂ 0.10c
13.10 ꢂ 0.03c
15.70 ꢂ 0.20bc
38.00 ꢂ 0.10d
95.00 ꢂ 0.00e
48.00 ꢂ 0.00e
80.00 ꢂ 1.60d
6.74 ꢂ 0.30a
5.80 ꢂ 0.20a
29.00 ꢂ 0.30b
6.74 ꢂ 0.30a
5.80 ꢂ 0.20a
40.60 ꢂ 0.20d
14.30 ꢂ 0.10b
28.70 ꢂ 0.20b
30.90 ꢂ 0.10d
44.16 ꢂ 0.20d
25.30 ꢂ 0.10c
32.20 ꢂ 0.07c
44.16 ꢂ 0.05e
58.60 ꢂ 0.20e
13.20 ꢂ 0.07b
26.40ꢂ 0.10b
25.40 ꢂ 0.10c
32.20 ꢂ 0.07c
47.80 ꢂ 0.00e
95.50 ꢂ 0.20g
13.10 ꢂ 0.03b
26.20 ꢂ 0.07b
38.00 ꢂ 0.20c
95.00 ꢂ 0.00g
48.00 ꢂ 0.20e
64.00 ꢂ 0.20f
3b
1.45 ꢂ 0.00a
9.00 ꢂ 0.20c
14.30 ꢂ 0.10c
23.00 ꢂ 0.00b
5.52 ꢂ 0.20b
27.60 ꢂ 0.20bc
12.60 ꢂ 0.20c
15.20 ꢂ 0.07a
5.52 ꢂ 0.07b
27.60 ꢂ 0.20bc
13.20 ꢂ 0.07c
21.10 ꢂ 0.03b
25.40 ꢂ 0.00d
32.20 ꢂ 0.07c
5.46 ꢂ 0.02b
21.40 ꢂ 0.10b
13.10 ꢂ 0.03c
21.00 ꢂ 0.00b
285.00 ꢂ 1.60f
380.00 ꢂ 1.70e
48.00 ꢂ 0.20e
64.00 ꢂ 0.30d
4a
nt
nt
4b
11.04 ꢂ 0.01b
27.60 ꢂ 0.2b
4c
nt
nt
4d
11.04 ꢂ 0.00b
27.60 ꢂ 0.20b
4e
nt
nt
nt
nt
4f
4g
5.46 ꢂ 0.05a
47.80 ꢂ 0.20c
4h
nt
nt
Ketoco-nazole
Bifona-zole
285.00 ꢂ 1.70d
380.00 ꢂ 1.70e
48.00 ꢂ 0.20c
64.00 ꢂ 0.00d
a
A. o. – Aspergillus ochraceus (ATCC 12066); A. v. – Aspergillus versicolor (ATCC 11730); A. . – Aspergillus avus (ATCC 9643); A. n. – Aspergillus niger
(ATCC 6275); A. fum. – Aspergillus fumigatus (human isolate).
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Table 4 Antifungal activity of title compounds (MIC and MFC in mmol mlꢀ1 ꢁ 10ꢀ2 a
)
Compounds
T. v.
P. o.
P. f.
C. a.
3a
MIC
MFC
MIC
MFC
MIC
MFC
MIC
MFC
MIC
MFC
MIC
MFC
MIC
MFC
MIC
MFC
MIC
MFC
MIC
MFC
MIC
MFC
MIC
MFC
2.52 ꢂ 0.20a
3.37 ꢂ 0.10a
3.37 ꢂ 0.02a
3.37 ꢂ 0.10a
6.74 ꢂ 0.20a
nt
3.37 ꢂ 0.10a
1.45 ꢂ 0.00a
29.00 ꢂ 0.03cd
28.70 ꢂ 0.20d
40.20 ꢂ 0.07e
27.60 ꢂ 0.20d
30.90 ꢂ 0.03d
12.60 ꢂ 0.10c
25.30 ꢂ 0.10c
5.52 ꢂ 0.20b
11.04 ꢂ 0.01b
13.20 ꢂ 0.07c
13.20 ꢂ 0.07b
12.70 ꢂ 0.00c
15.20 ꢂ 0.07b
10.92 ꢂ 0.03c
47.80 ꢂ 0.03e
13.10 ꢂ 0.03c
21.00 ꢂ 0.03c
475.00 ꢂ 1.70g
570.00 ꢂ 1.70g
64.0 ꢂ 0.00e
80.0 ꢂ 0.03f
5.05 ꢂ 0.20a
34.80 ꢂ 0.30d
40.60 ꢂ 0.7e
14.30 ꢂ 0.10b
28.70 ꢂ 0.20c
30.90 ꢂ 0.30d
44.16 ꢂ 0.05e
25.30 ꢂ 0.10c
32.20 ꢂ 0.07d
27.60 ꢂ 0.00c
44.60 ꢂ 0.10e
26.4 ꢂ 0.10c
37.00 ꢂ 0.00d
25.40 ꢂ 0.10c
32.20 ꢂ 0.07d
21.40 ꢂ 0.10c
47.80 ꢂ 0.03e
13.10 ꢂ 0.00b
15.70 ꢂ 0.20b
380.0 ꢂ 1.70f
380.0 ꢂ 1.70g
48.0 ꢂ 0.00e
64.0 ꢂ 0.03f
6.74 ꢂ 0.20a
34.80 ꢂ 0.30d
34.80 ꢂ 0.30c
28.70 ꢂ 0.10c
40.20 ꢂ 0.07d
11.04 ꢂ 0.10b
30.90 ꢂ 0.30c
25.30 ꢂ 0.10c
32.20 ꢂ 0.07c
27.60 ꢂ 0.20c
44.16 ꢂ 0.050d
26.40 ꢂ 0.00c
37.00 ꢂ 0.00cd
25.40 ꢂ 0.10c
32.20 ꢂ 0.07c
10.92 ꢂ 0.30b
27.30 ꢂ 0.10b
26.20 ꢂ 0.07c
36.70 ꢂ 0.20c
38.00 ꢂ 0.00d
95.00 ꢂ 0.30f
64.00 ꢂ 0.20e
80.00 ꢂ 1.00e
3b
nt
4a
17.20 ꢂ 0.07b
23.00 ꢂ 0.00b
nt
4b
nt
4c
25.30 ꢂ 0.10c
30.40 ꢂ 0.10c
nt
4d
nt
4e
26.40 ꢂ 0.10c
37.00 ꢂ 0.30cd
30.50 ꢂ 0.20cd
40.60 ꢂ 0.20d
nt
4f
4g
nt
4h
15.70 ꢂ 0.10b
26.2 ꢂ 0.07bc
37.60 ꢂ 0.00d
94.00 ꢂ 0.30e
32.20 ꢂ 0.07cd
48.30 ꢂ 0.10d
Ketoconazole
Bifonazole
a
T. v. – Trichoderma viride (IAM 5061); P. o. – Penicillium ochrochloron (ATCC 9112); P. f. – Penicillium funiculosum (ATCC 36839); C. a. – Candida
albicans (human isolate).
be mentioned that all the title compounds were much more within 0.4% of theoretical values. IR spectra were recorded, as
potent than commercial antifungals, ketoconazole with fungi- Nujol mulls, on a Perkin Elmer Spectrum BX. Wave-numbers in
static activity at 38.0–475.0 ꢁ 10ꢀ2 mmol mlꢀ1 and fungicidal the IR spectra are given in cmꢀ1. 1H NMR and 13C NMR spectra of
effects at 38.0–475.0 ꢁ 10ꢀ2 mmol mlꢀ1, while the MIC of bifo- the newly synthesized compounds, in DMSO-d6 or CDCl3 solu-
nazole was in the range of 32.0–64.0 ꢁ 10ꢀ2 mmol mlꢀ1 and tions, were recorded on a Bruker AC 300 instrument (Bruker,
MFCs at 95.0–570.0 ꢁ 10ꢀ2 mmol mlꢀ1
.
Karlsruhe, Germany) at 298 K. Chemical shis are reported as d
Compound 3b exhibited the best activity against A. ochraceus (ppm) relative to TMS as an internal standard. Coupling constants
(MIC at 1.45 mmol ꢁ 10ꢀ2 mlꢀ1 and MFC at 5.8 mmol ꢁ 10ꢀ2 J are expressed in Hertz (Center of Instrumental Analysis of the
mlꢀ1), while the highest potential against A. versicolor was University of Thessaloniki). Mass spectra were recorded on an ESI-
observed for compound 4g followed by 4d and 4b. As far as A. MS (Micromass ZMD Waters) at a cone voltage of 30 V. The reac-
avus is concerned, the most active appeared to be compound tions were monitored by TLC on F254 silica-gel precoated sheets
3a followed by 4d and 4b, while 3a was the best against A. (Merck, Darmstadt, Germany) and each of the puried compounds
fumigatus. Compounds 4a, 4c and 4f were also potent against showed a single spot. Solvents, unless otherwise specied, were of
the previously mentioned fungus.
analytical reagent grade or of the highest quality commercially
The relationship between the structure and the antifungal available. Synthetic starting materials, reagents and solvents were
activity revealed that for compounds 4a–c the order of their purchased from Aldrich Chemie (Steinheim, Germany).
activity is in agreement with that observed for antibacterial
potential (4c > 4a > 4b). It was found that the presence of
methoxy- and chloro-substituents at the benzene ring endowed
higher potential to methylamino derivatives. On the other hand,
4-Me, 4-NO2 and 4-F (4d, 4f and 4g) groups had a negative effect
3.1. General synthesis of 1-(4-methyl-2-(alkylamino)thiazol-
5-yl)ethanone22
1-Alkylthiourea (0.02 mol) was dissolved in acetone (50 ml). 3-
chloroacetylacetone (2.26 ml, 0.02 mol) diluted in acetone (5 ml)
was added dropwise and the mixture was reuxed for 1.5 h. The
solid product was ltered and re-crystallized from ethanol.
compared to the parent compound (4a).
3. Experimental
3.2. General synthesis of 1-(4-methyl-2-phenylthiazol-5-yl)
ethanone21,22
Melting points (ꢃC) were determined using a MELTEMP II capillary
apparatus (LAB Devices, Holliston, MA, USA) without correction.
Elemental analyses were performed using a Perkin-Elmer 2400 Thiobenzamide (2.74 g, 0.02 mol) was dissolved in absolute
CHN elemental analyzer and all compounds synthesized were ethanol (15 ml). 3-Chloroacetylacetone (2.26 ml, 0.02 mol)
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diluted in absolute ethanol (2 ml) was added dropwise and the
mixture was reuxed for 3 h. Aer cooling at room temperature,
the solution was transferred to an ice bath and H2O (15 ml)
was added under continuous stirring. The precipitate was
ltered under vacuum and re-crystallized from petroleum
ether–ethanol.
3.5.1. 5-(1,5-Diphenyl-4,5-dihydro-1H-pyrazol-3-yl)-N,4-
1
ꢃ
dimethylthiazol-2-amine (4a). Yield: 58%, mp: 255–257 C. H
NMR (d ppm, DMSO-d6, 300 MHz): 2.36 (s, 3H, thiazole 4-CH3),
3.06 (s, 3H, thiazole NCH3), 3.14 (dd, J1 ¼ 17.1, J2 ¼ 6.9 Hz, 1H,
CHAHBC]N), 4.02 (dd, J1 ¼ 17.1, J2 ¼ 12.3 Hz, 1H, CHAHBC]
N), 5.47 (dd, J1 ¼ 12.3, J2 ¼ 6.9 Hz, 1H, ArCHN), 6.71–7.39 (m,
10H, ArH). 13C NMR (d ppm, DMSO-d6, 75 MHz): 13.62, 32.57,
44.28, 64.40, 111.75, 113.43, 119.52, 126.39, 128.07, 129.39,
129.52, 141.49, 142.38, 144.12, 166.88. MS: (m/z): 350 (M+ + 2,
31%), 349 (M+ + 1, 100%), 348 (M+, 58%), 259 (18%). Anal. calcd
for C20H20N4S (MW 348): C, 68.93; H, 5.79; N, 16.08. Found: C,
68.95; H, 5.78; N, 16.07%.
3.3. General procedure for the synthesis of chalcone
precursors21,22
1-(4-Methyl-2-(alkylamino/phenyl)thiazol-5-yl)ethanone (1 mol)
in methanol (4.0–4.1 l) was added dropwise to a cooled solution
of corresponding aromatic aldehydes (1 mol) in 10% NaOH
(600–650 ml). The reaction mixture was kept under stirring at
0 ꢃC for 30 min and aerwards at room temperature for several
hours (5–12 h) until solid started separating out. The solid was
ltered under vacuum, washed with H2O and re-crystallized
from dioxane to give the corresponding chalcones.
3.5.2. 5-(1,5-Diphenyl-4,5-dihydro-1H-pyrazol-3-yl)-N-ethyl-
1
ꢃ
4-methylthiazol-2-amine (4b). Yield: 54%, mp: 223–225 C. H
NMR (d ppm, CDCl3, 300 MHz): 1.42 (t, J ¼ 6.9 Hz, 3H,
NCH2CH3), 2.39 (s, 3H, thiazole 4-CH3), 3.12 (dd, J1 ¼ 17.1, J2 ¼
7.5 Hz, 1H, CHAHBC]N), 3.41 (q, J ¼ 6.9 Hz, 2H, NCH2CH3),
3.82 (dd, J1 ¼ 17.1, J2 ¼ 12.3 Hz, 1H, CHAHBC]N), 5.32 (dd, J1 ¼
12.3, J2 ¼ 7.5 Hz, 1H, ArCHN), 6.79–7.38 (m, 10H, ArH), 9.54 (s,
1H, NH). Anal. calcd for C21H22N4S (MW 362): C, 69.58; H, 6.12;
N, 15.46. Found: C, 69.59; H, 6.14; N, 15.48%.
3.4. General procedure for the synthesis of aminopyrimidine
derivatives (3a,b)18,19
A mixture of corresponding chalcones (0.01 mol) and guanidine
hydrochloride (1.433 g, 0.015 mol) was dissolved under stirring
in the minimum quantity of hot absolute ethanol. A solution of
10% NaOH was added dropwise until pH became basic and the
reaction mixture was reuxed for 27–32 h. Aer evaporation of
solvent under vacuum, the residue was extracted with chloro-
form. The organic phases were collected, dried with anhydrous
Na2SO4, ltered and the solvent was evaporated under vacuum.
The crude product was puried by ash column chromatog-
raphy (petroleum ether–ethyl acetate) and the yield of
compounds was between (3a,b) 15 and 27%.
3.4.1. 5-(2-Amino-6-phenylpyrimidin-4-yl)-N,4-dimethylth-
iazol-2-amine (3a). Yield: 15%, mp: 195–196 ꢃC. 1H NMR (d
ppm, DMSO-d6, 300 MHz): 2.83 (s, 3H, thiazole 4-CH3), 3.26 (s,
3H, thiazole NCH3), 7.09 (s, 1H, ArH), 7.49–8.06 (m, 5H, ArH).
Anal. calcd for C15H15N5S (MW 297): C, 60.58; H, 5.08; N, 23.55.
Found: C, 60.56; H, 5.09; N, 23.56%.
3.5.3. 5-(1,5-Diphenyl-4,5-dihydro-1H-pyrazol-3-yl)-4-methyl-
1
ꢃ
2-phenylthiazole (4c). Yield: 74%, mp: 151–152 C. H NMR (d
ppm, CDCl3, 300 MHz): 2.76 (s, 3H, thiazole 4-CH3), 3.21 (dd, J1 ¼
17.1, J2 ¼ 7.5 Hz, 1H, CHAHBC]N), 3.90 (dd, J1 ¼ 17.1, J2 ¼ 12.3
Hz, 1H, CHAHBC]N), 5.30 (dd, J1 ¼ 12.3, J2 ¼ 7.5 Hz, 1H,
ArCHN), 6.80–7.98 (m, 15H, ArH). Anal. calcd for C25H21N3S (MW
395): C, 75.92; H, 5.35; N, 10.62. Found: C, 75.91; H, 5.34; N,
10.64%.
3.5.4. N-4-Dimethyl-5-(1-phenyl-5-p-tolyl-4,5-dihydro-1H-
ꢃ
pyrazol-3-yl)thiazol-2-amine (4d). Yield: 48%, mp: 217–219 C.
1H NMR (d ppm, CDCl3, 300 MHz): 2.35 (s, 3H, Ar-CH3), 2.41 (s,
3H, thiazole 4-CH3), 3.09 (dd, J1 ¼ 17.1, J2 ¼ 7.5 Hz, 1H,
CHAHBC]N), 3.15 (s, 3H, thiazole NCH3), 3.82 (dd, J1 ¼ 17.1, J2
¼ 12.3 Hz, 1H, CHAHBC]N), 5.31 (dd, J1 ¼ 12.3, J2 ¼ 7.5 Hz, 1H,
ArCHN), 6.81–7.21 (m, 9H, ArH), 9.76 (s, 1H, NH). Anal. calcd for
C
21H22N4S (MW 362): C, 69.58; H, 6.12; N, 15.46. Found: C,
69.57; H, 6.14; N, 15.47%.
3.4.2. 4-(4-Methyl-2-phenylthiazol-5-yl)-6-phenylpyrimidin-
2-amine (3b). Yield: 27%, mp: 180–181 ꢃC. 1H NMR (d ppm,
CDCl3, 300 MHz): 2.88 (s, 3H, thiazole 4-CH3), 7.36–8.03 (m,
11H, ArH). 13C NMR (d ppm, CDCl3, 75 MHz): 18.58, 104.98,
126.58, 127.15, 128.88, 129.02, 130.45, 130.72, 131.75, 133.35,
137.44, 153.43, 159.99, 163.22, 166.25, 167.55. MS: (m/z): 346
(M+ + 2, 66%), 345 (M+ + 1, 100%), 163 (18%). Anal. calcd for
3.5.5. 5-(5-(4-Methoxyphenyl)-1-phenyl-4,5-dihydro-1H-pyr-
azol-3-yl)-N,4-dimethylthiazol-2-amine (4e). Yield: 31%, mp:
203–205 ꢃC. 1H NMR (d ppm, CDCl3, 300 MHz): 2.42 (s, 3H,
thiazole 4-CH3), 3.15 (s, 3H, thiazole NCH3), 3.73 (dd, J1 ¼ 17.1,
J2 ¼ 7.5 Hz, 1H, CHAHBC]N), 3.81 (s, 3H, OCH3), 3.86 (dd, J1 ¼
17.1, J2 ¼ 12.3 Hz, 1H, CHAHBC]N), 5.31 (dd, J1 ¼ 12.3, J2 ¼ 7.5
Hz, 1H, ArCHN), 6.82–7.28 (m, 9H, ArH), 9.80 (s, 1H, NH). Anal.
calcd for C21H22N4OS (MW 378): C, 66.64; H, 5.86; N, 14.80.
Found: C, 66.65; H, 5.88; N, 14.78%.
C
20H16N4S (MW 344): C, 69.74; H, 4.68; N, 16.27. Found: C,
69.76; H, 4.66; N, 16.28%.
3.5.6. N,4-Dimethyl-5-(5-(4-nitrophenyl)-1-phenyl-4,5-dihy-
dro-1H-pyrazol-3-yl)thiazol-2-amine (4f). Yield: 42%, mp: 239–
240 ꢃC. 1H NMR (d ppm, DMSO-d6, 300 MHz): 2.35 (s, 3H,
thiazole 4-CH3), 3.04 (s, 3H, thiazole NCH3), 3.21 (dd, J1 ¼ 17.1,
J2 ¼ 6.9 Hz, 1H, CHAHBC]N), 4.06 (dd, J1 ¼ 17.1, J2 ¼ 12.3 Hz,
1H, CHAHBC]N), 5.67 (dd, J1 ¼ 12.3, J2 ¼ 6.9 Hz, 1H, ArCHN),
6.73–6.78 (m, 1H, ArH), 6.88 (d, J ¼ 7.8 Hz, 2H, ArH), 7.14–7.19
(m, 2H, ArH), 7.57 (d, J ¼ 8.7 Hz, 2H, ArH), 8.23 (d, J ¼ 8.7 Hz,
2H, ArH), 9.81 (s, 1H, NH). Anal. calcd for C20H19N5O2S
3.5. General procedure for the synthesis of N-
phenylpyrazoline derivatives (4a–h)20
0.01 mol of corresponding chalcones was dissolved under stir-
ring in the minimum quantity of hot absolute ethanol. Phe-
nylhydrazine hydrochloride (2.168 g, 0.015 mol) was added and
the mixture was reuxed for 35–40 h. The precipitate was
ltered under vacuum, washed with water and recrystallized
from ethanol to give the corresponding pyrazolines. The yield
range aer recrystallization of pyrazolines (4a–h) was 31–74%.
920 | Med. Chem. Commun., 2014, 5, 915–922
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(MW 393): C, 61.05; H, 4.87; N, 17.80. Found: C, 61.06; H, 4.85; killing of the original inoculum. The optical density of each well
N, 17.82%. was measured at a wavelength of 655 nm by using a Microplate
3.5.7. 5-(5-(4-Fluorophenyl)-1-phenyl-4,5-dihydro-1H-pyr- manager 4.0 (Bio-Rad Laboratories) and compared with a blank
azol-3-yl)-N,4-dimethylthiazol-2-amine (4g). Yield: 58%, mp: and the negative control (DMSO). Streptomycin (Sigma P 7794)
1
177–179 ꢃC. H NMR (d ppm, DMSO-d6, 300 MHz): 2.43 (s, 3H, and ampicillin (Panfarma, Belgrade, Serbia) were used as
thiazole 4-CH3), 3.01–3.26 (m, 4H, thiazole NCH3, CHAHBC]N), positive controls (1 mg mlꢀ1 DMSO). All experiments were
3.84 (dd, J1 ¼ 17.1, J2 ¼ 12.3 Hz, 1H, CHAHBC]N), 5.34 (dd, J1 ¼ performed in duplicate and repeated three times.
12.3, J2 ¼ 6.9 Hz, 1H, ArCHN), 6.86–7.28 (m, 9H, ArH), 9.74 (s,
3.6.3. Antifungal activity. For the antifungal bioassays,
1H, NH). Anal. calcd for C20H19FN4S (MW 366): C, 65.55; H, eight fungi were used: Aspergillus ochraceus (ATCC 12066),
5.23; N, 15.29. Found: C, 65.57; H, 5.22; N, 15.32%. Aspergillus avus (ATCC 9643), Aspergillus fumigatus (plant
3.5.8. 5-(5-(4-Chlorophenyl)-1-phenyl-4,5-dihydro-1H-pyr- isolate), Aspergillus niger (ATCC 6275), Aspergillus versicolor
azol-3-yl)-N,4-dimethylthiazol-2-amine (4h). Yield: 51%, mp: (ATCC 11730), Penicillium funiculosum (ATCC 36839), Penicillium
215–217 ꢃC. 1H NMR (d ppm, CDCl3, 300 MHz): 2.43 (s, 3H, ochrochloron (ATCC 9112), Trichoderma viride (IAM 5061) and
thiazole 4-CH3), 3.08–3.15 (m, 4H, thiazole NCH3, CHAHBC]N), Candida albicans ATCC 10231. The organisms were obtained
3.85 (dd, J1 ¼ 17.1, J2 ¼ 12.3 Hz, 1H, CHAHBC]N), 5.34 (dd, J1 ¼ from the Mycological Laboratory, Department of Plant Physi-
ˇ
´
12.3, J2 ¼ 7.5 Hz, 1H, ArCHN), 6.85–7.38 (m, 9H, ArH), 9.81 (s, ology, Institute for Biological Research “Sinisa Stankovic”, Bel-
1H, NH). Anal. calcd for C20H19ClN4S (MW 382.5): C, 62.73; H, grade, Serbia.
5.00; N, 14.63. Found: C, 62.76; H, 5.01; N, 14.60%.
The micromycetes were maintained on malt agar and the
cultures were stored at 4 ꢃC and sub-cultured once a month.26 In
order to investigate the antifungal activity of the compounds, a
modied microdilution technique was used.30–32 The fungal
3.6. Biological evaluation
3.6.1. Antibacterial activity. The following Gram-negative spores were washed from the surface of agar plates with sterile
bacteria were used: Escherichia coli (ATCC 35210), Pseudomonas 0.85% saline containing 0.1% Tween 80 (v/v). The spore
aeruginosa (ATCC 27853), Salmonella typhimurium (ATCC suspension was adjusted with sterile saline to a concentration
13311), and Enterocbacter cloacae (ATCC 35030) and the of approximately 1.0 ꢁ 105 in a nal volume of 100 ml per well.
following Gram-positive bacteria were used: Staphylococcus The inocula were stored at 4 ꢃC for further use. Dilutions of the
aureus (ATCC 6538), Bacillus cereus (clinical isolate), Micrococcus inocula were cultured on solid malt agar to verify the absence of
avus (ATCC 10240), Listeria monocytogenes (NCTC 7973) and contamination and to check the validity of the inoculum.
Enterococcus faecalis (ATCC 7080). The organisms were obtained
Minimum inhibitory concentration (MIC) determinations
from the Mycological Laboratory, Department of Plant Physi- were performed by a serial dilution technique using 96-well
ˇ
´
ology, Institute for Biological Research “Sinisa Stankovic”, Bel- microtiter plates. The compounds investigated were dissolved
grade, Serbia.
in DMSO (1 mg mlꢀ1) and added in broth malt medium with
The antibacterial assay was carried out by a microdilution inoculum. The microplates were incubated for 72 h at 28 ꢃC.
method29,30 in order to determine the antibacterial activity of The lowest concentrations without visible growth (at the
compounds tested against the human pathogenic bacteria.
The bacterial suspensions were adjusted with sterile saline
binocular microscope) were dened as MICs.
The fungicidal concentrations (MFCs) were determined by
to a concentration of 1.0 ꢁ 105 CFU mlꢀ1. The inocula were serial subcultivation of 2 ml into microtiter plates containing
ꢃ
prepared daily and stored at +4 C until use. Dilutions of the 100 ml of broth per well and further incubation for 72 h at 28 ꢃC.
inocula were cultured on solid medium to verify the absence of The lowest concentration with no visible growth was dened as
contamination and to check the validity of the inoculum.
the MFC indicating 99.5% killing of the original inoculum.
All experiments were performed in duplicate and repeated DMSO was used as a negative control, commercial fungicides,
three times.
bifonazole (Srbolek, Belgrade, Serbia) and ketoconazole (Zor-
ˇ
3.6.2. Microdilution test. The minimum inhibitory and kapharma, Sabac, Serbia), were used as positive controls (1–
bactericidal concentrations (MICs and MBCs) were determined 3000 mg mlꢀ1). All experiments were performed in duplicate and
using 96-well microtitre plates. The bacterial suspension was repeated three times.
adjusted with sterile saline to a concentration of 1.0 ꢁ 105 CFU
3.6.4. Statistical analysis. All the assays were carried out in
mlꢀ1. The compounds investigated were dissolved in DMSO triplicate and the results are expressed as mean values and
(1 mg mlꢀ1) and added in broth TSB medium (100 ml) with standard deviation (SD). The results were analyzed using one-
bacterial inoculum (1.0 ꢁ 104 CFU per well) to achieve the way analysis of variance (ANOVA) followed by Tukey's HSD test
desired concentrations (1 mg mlꢀ1). The microplates were with a ¼ 0.05. This treatment was carried out using the SPSS v.
incubated for 24 h at 48 ꢃC. The lowest concentrations without 18.0 program.
visible growth (at the binocular microscope) were dened as
concentrations that completely inhibited bacterial growth
(MICs). The MBCs were determined by serial sub-cultivation of
4. Conclusions
2 ml into microtitre plates containing 100 ml of broth per well The newly synthesized thiazole-based aminopyrimidines 3a,b
and further incubation for 72 h. The lowest concentration with and N-phenylpyrazolines 4a–h exhibit a remarkable inhibition
no visible growth was dened as the MBC, indicating 99.5% of the growth of a wide spectrum of Gram positive, Gram
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MedChemComm
Concise Article
negative bacteria and fungi. Almost all our compounds exhibi- 13 H. S. Shah and S. P. Patel, Chem. Sci. Trans., 2012, 1(3), 632.
ted better or comparable antibacterial activity to reference 14 M. Ghannoum, K. Abu Elteen and N. R. el-Rayyes, Microbios,
drugs with the most potent being compound 3a followed by 4f.
1989, 60(242), 23.
The most sensitive bacterial species on these compounds are L. 15 S. Chandrasekaran and S. Nagarajan, Il Farmaco, 2005, 60,
monocytogenes and S. aureus, while En. faecalis and En. cloacae
are the more resistant ones.
As far as the fungi are concerned, the tested compounds
possess excellent activity against all the fungal species tested,
279.
16 I. G. Rathish, K. Javed, S. Ahmad, S. Bano, M. S. Alam,
K. K. Pillai, S. Singh and V. Bagchi, Bioorg. Med. Chem.
Lett., 2008, 21, 212.
being more active than ketoconazole and bifonazole. The most 17 M. T. Chhabria, H. G. Bhatt, H. G. Raval and P. M. Oza,
promising are compounds 3a followed by 4h. The most sensi- Bioorg. Med. Chem. Lett., 2007, 17(4), 1022.
tive fungi were A. ochraceus and A. versicolor, while A. niger and 18 H. B. Shivarama, P. M. Akberali and M. K. Shivananda, Il
C. albicans were the most resistant ones. Farmaco, 2000, 55, 256.
It can be seen that the growth of tested bacteria (Gram (ꢀ) 19 A. Agarwal, K. Srivastava, S. K. Puri and M. S. P. Chauhan,
and Gram (+) bacteria) and fungi responded differently to the Bioorg. Med. Chem., 2005, 13, 6226.
tested compounds, which indicates that different components 20 Y. R. Prasad, A. L. Rao, L. Prasoona, K. Murali and
may have different modes of action or that the metabolism of P. R. Kumar, Bioorg. Med. Chem. Lett., 2005, 15, 5030.
´
ˇ
´
some bacteria/fungi is able to better overcome the effect of the 21 K. Liaras, A. Geronikaki, J. Glamoclija, A. Ciric and
´
compounds or adapt to it. Gram (ꢀ) bacteria and fungi are in
M. Sokovic, Bioorg. Med. Chem., 2011, 19(10), 3135.
general more resistant than Gram (+) bacteria.33
22 K. Liaras, A. Geronikaki, J. Glamoclija, A. Ciric and
´
ˇ
´
´
M. Sokovic, Bioorg. Med. Chem., 2011, 19(24), 7349.
23 I. Rahavi, Ch. Kamoutsis, P. Zoumpoulakis, A. Geronikaki,
Notes and references
´
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