M. A. Bhat et al. / Bioorg. Med. Chem. Lett. 24 (2014) 1299–1302
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Table 2
Anti-Candidal activity of the compounds (2a–r) as MIC values (
l
g/mL)
Compound C. tropicalis
C. parapsilosis C. albicans
Candida sp.
[HVS*]
Candida sp.
[HVS] 11972 [HVS] 178
Candida sp. Candida sp.
Candida sp.
[urine]
Candida sp.
[urine]
Candida sp.
[blood]
ATCC 66029 ATCC 22019
ATCC
[urine] 300
66027
13184
12341
12485
12810
2a
2b
2c
2d
2e
2f
2g
2h
2i
1.6
0.39
>50
0.19
>50
0.78
>50
>50
>50
>50
>50
>50
0.78
>50
>50
0.19
>50
0.19
6.25
0.04
0.19
>50
0.09
>50
0.78
>50
>50
>50
>50
>50
>50
0.19
>50
>50
0.39
>50
0.39
1.6
12.5
>50
0.78
>50
6.25
>50
>50
>50
>50
>50
>50
6.25
>50
>50
1.6
6.25
>50
0.19
>50
12.5
>50
>50
>50
>50
>50
>50
0.39
>50
>50
0.78
>50
0.19
6.25
0.02
6.25
>50
0.19
>50
6.25
>50
>50
>50
>50
>50
>50
6.25
>50
>50
0.19
>50
0.09
0.39
0.19
0.19
>50
0.39
>50
0.78
>50
>50
>50
>50
>50
>50
0.78
>50
>50
1.6
1.6
1.6
0.78
>50
0.09
>50
1.6
>50
>50
>50
>50
>50
>50
0.09
>50
>50
1.6
>50
0.19
>50
0.78
>50
>50
>50
>50
>50
>50
1.6
>50
>50
0.19
>50
0.19
0.19
0.19
>50
0.19
>50
6.25
>50
>50
>50
>50
>50
>50
0.78
>50
>50
1.6
>50
0.39
>50
6.25
>50
>50
>50
>50
>50
>50
6.25
>50
>50
1.6
2j
2k
2l
2m
2n
2o
2p
2q
2r
>50
1.6
0.78
0.39
>50
1.6
1.6
>50
0.19
6.25
0.09
>50
0.78
0.39
0.04
>50
0.39
0.39
0.25
IT#
1.56
0.09
*
HVS: High Vaginal Swab.
IT: itraconazole.
#
Table 3
In vitro cytotoxicity of the compounds against cancer cell lines
25 lg/mL against a fluconazole) was chosen as the first hit for fur-
ther derivatization.6 Replacement of the isoquinoline nucleus by
pyridine and preserving the pharmacophore [A(C@O)ANHANHA
(C@S)ANHAR] was studied. Surprisingly when the R was changed
by electron donating groups (compounds 2d, 2f, 2i, 2j, 2k, 2m and
2n), the anti-Candidal activity was lost. Insertion of cyclohexy
group, 2b also led to the loss of activity. These disappointing re-
sults led us to switch to the electron withdrawing groups. Com-
pounds 2c, 2q, 2l, 2o and 2r achieved the strongest anti-Candida
activity. The best activity was observed when phenyl was replaced
by p-chlorophenyl group, compound 2c presents a good anti-Can-
dida activity with a selectivity oriented towards C. albicans ATCC
Compound
IC50 (lg/mL)
HT 1080 (Skin)
HepG2 (Liver)
A549 (Lung)
2c
2r
2a
540.12
833.4
684.14
201.63
1200.5
409.55
715.83
142
409.55
813
2042.5
182
Itraconazole
the compounds (2a–r) were evaluated against non cancer cell line;
MCF-10A (non-tumorigenic epithelial cell line) for their cytotoxic
properties using WST-1 assay. None of the active compounds
showed any cytotoxicity to non cancer cell line up to highest con-
66027 and Candida spp. 12810 [blood] (MIC, 0.09 lg/mL). In partic-
ular, this compound showed similar to better activity than refer-
ence drug for several Candida strains. The compound with p-iodo
substitution on the phenyl group was found to be more active
centration of (IC50 >300 lM), indicating a high selectivity of anti-
against Candida spp. 178 [HVS] with (MIC, 0.09
pound with m-chloro substitution on phenyl group was found to
be active against Candida spp. 12810 [blood] with (MIC, 0.09 g/
mL) whereas itraconazole exhibits inhibitory activity with (MIC,
0.04–1.56 g/mL). The compound 2c bearing p-chloro substitution
lg/mL) and com-
Candidal activity. The compounds 2c, 2r and 2a were evaluated
against three cancer celines; HT1080 (skin), HepG2 (Liver), A549
(Lung) using MTT assay (Table 3). The biological study indicated
that screened compounds showed minimal cytotoxicity (IC50
l
l
>400 lg/mL), against all three cancer cell lines.
on phenyl group was found to be most potent derivative of the
series against all strains of Candida spp. This could result from
increased lipophilicity associated with chloro phenyl group. The
biological results indicate that C. albicans ATCC 66027 was more
susceptible to compounds 2a, 2c, 2e, 2l, 2o and 2q (MIC, 0.09–
In conclusion we focused on the synthesis of thiosemicarbazide
derivatives of isoniazid (2a–r) which were screened in vitro against
ten strains of Candida spp. The compounds bearing p-chlorophenyl,
p-iodophenyl, m-chlorophenyl, o-nitrophenyl and p-acetamido
substitution were more active than the compounds bearing meth-
ylphenyl, methoxyphenyl, cyclohexyl, sulfonamidophenyl and eth-
oxyphenyl against all Candida spp. Compound 2c was the most
effective compound against C. albicans ATCC66027 and Candida
0.78
da tropicalis ATCC 66029 was equally susceptible to compounds 2c,
2o, 2q and 2r (MIC, 0.19 g/mL) as to itraconazole (0.19 g/mL).
Candida spp. 178 [blood] was more susceptible to compounds 2c,
2o and 2q (MIC, 0.09–0.19 g/mL) as compared to itraconazole
(MIC, 0.19 g/mL). It is apparent that there is a positive correlation
lg/mL) as compared to itraconazole (MIC, 1.56 lg/mL). Candi-
l
l
spp. [blood] (MIC, 0.09 lg/mL). This outcome confirms that p-
l
chlorophenyl substitution have a considerable influence on anti-
Candidal activity. The active compounds showed lowest cytotoxic-
ity against tested three cancer cell lines and non cancer cell line.
Based on the reported results, compounds 2c, 2q, 2l, 2r and 2o
could also be used in association with azole derivatives to evaluate
their antifungal activity. Moreover, compound 2c displaying better
activity against C. albicans ATCC66027 and Candida spp. [blood]
compared to reference drug (itraconazole), represents a good lead
for the development of newer, potent and broad spectrum anti-
Candidal agents.
l
between anti-Candidal activity and electronegative functional
groups like chloro, iodo and nitro. The hydrophobicity balance
was already proved to be important in such series to obtains anti
Candida activity.29 From a pharmacological point of view it is
important for the studied compounds to exhibit high bioactivity
and at the same time show no or low cytotoxicity effects, other-
wise the activity might just be due to general toxicity, which dis-
qualifies the compound as a drug or lead molecule candidate. All