Arch. Pharm. Chem. Life Sci. 2006, 339, 267–272
Analgesic Activity of Pyrazolylazo Derivatives
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pyrazole C5 methyl), 2.81 (s, 3H, pyrazole C3 methyl), 3.20 (t, 2H, –
CH2CH2C6H5), 3.90 (q, 2H, –CH2CH2C6H5), 4.01 (q, 2H, –CH2CH2OH),
4.35 (t, 2H, –CH2CH2OH), 5.25 (t, 1H, –CH2CH2OH), 7.43–7.55 (m,
5H, –CH2CH2C6H5), 8.06 (d, J= 8.0 Hz, 2H, ortho-protons to azo),
8.31 (d, J= 8.0 Hz, 2H, meta-protons to azo); 8.37 (s, 1H, –
NHNHCSNH–), 9.56 (s, 1H, –NHNHCSNH–), 10.60 (s, 1H, –
NHNHCSNH–). MS (ES) [M+H]+: m/z 466.
8.2 Hz 2H, meta-protons to azo), 13.99 (s, 1H, NH proton of tria-
zole). MS (ES) [M+H]+: m/z 426.
4-[((1-(2-Hydroxyethyl)-3,5-dimethylpyrazole-4-
yl)azo)phenyl]-4-(2-phenethyl)-2,4-dihydro-3H-1,2,4-
triazole-3-thione 4c
2-(Butylamino)-5-[((1-(2-hydroxyethyl)-3,5-
IR (KBr): 3462 (O–H and N–H), 2932 (=C–H), 1625 (C=N), 1419
(N=N), 1245 (C=S) cm–1. 1H-NMR d (ppm): 2.42 (s, 3H, pyrazole C5
methyl), 2.62 (s, 3H, pyrazole C3 methyl), 2.99 (t, 2H, –
CH2CH2C6H5), 3.76 (q, 2H, –CH2CH2OH), 4.12 (t, 2H, –CH2CH2C6H5),
4.28 (t, 2H, –CH2CH2OH), 4.94 (t, 1H, –CH2CH2OH), 7.00-7.23 (m,
5H, –CH2CH2C6H5), 7.58 (d, J= 8.4 Hz, 2H, meta-protons to azo),
7.81 (d, J= 8.4 Hz, 2H, ortho-protons to azo), 14.01 (s, 1H, NH pro-
ton of triazole). MS (ES) [M+H]+: m/z 447.
dimethylpyrazole-4-yl)azo)phenyl]-1,3,4-thiadiazole 3a
IR (KBr): 3177 (O–H and N–H), 2929 (=C–H), 1550 (C=N), 1420
(N=N), 668 (C–S–C) cm–1. 1H-NMR d (ppm): 0.92 (t, 3H, –
NHCH2CH2CH2CH3), 1.33 (m, 2H, –NHCH2CH2CH2CH3), 1.56 (m,
2H, –NHCH2CH2CH2CH3), 2.41 (s, 3H, pyrazole C5 methyl), 2.61 (s,
3H, pyrazole C3 methyl), 3.24 (m, 2H, –NHCH2CH2CH2CH3), 3.75
(q, 2H, –CH2CH2OH), 4.11 (t, 2H, –CH2CH2OH), 5.25 (t, 1H, –
CH2CH2OH), 7.82 (d, J= 8.5 Hz, 2H, ortho-protons to azo,), 7.86 (d,
J= 8.5 Hz 2H, meta-protons to azo), 8.10 (s, 1H, –NH–). MS (ES)
[M+H]+: m/z 400.
Pharmacology
All experimental protocols were approved by the Marmara Uni-
versity School of Medicine Animal Care and Use Committee.
Adult Balb/C male and female mice (25-30 g) were used in the
study. They were housed in a quiet, temperature- (20 € 28C) and
humidity- (60 € 3%) controlled room, where a 12/12 h light-dark
cycle was maintained (07:00–19:00 light). The mice were fed
standard lab chow and tap water ad lib during the study. The
thermal techniques (tail-immersion [24] and hot-plate [25]) were
used to evaluate both basal nociceptive threshold and the
analgesic effect of the compounds 2a–c, 3a–c, and 4a–c. All sub-
stances were suspended in 0.5% methyl cellulose (MC) and admi-
nistered at a dose of 100 mg/kg by intraperitoneal injection (i.p.)
in a volume of 0.1 mL/10 g. Control animals received the vehicle
which is 0.5% MC. For the reference analgesic drug morphine,
HCl was suspended in the same vehicle and given at a dose of
5 mg/kg. Bederson-modified neurological examination [26] was
also conducted with mice to verify that the dose used did not
produce neurological side effects. Briefly, in the hot-plate test,
the licking of the hind paw or jumping was measured as hot-
plate latency at 558C and in the tail-immersion test, the mice
tails were immersed in warm water (558C) which provokes an
abrupt movement of the tail and sometimes the recoiling of the
whole body. Analgesia is defined as the increase in the baseline
latency. Mice were either injected with vehicle (control group),
morphine hydrochloride (reference analgesic for both tests)
5 mg/kg i.p., or compounds 100 mg/kg i.p. Test duration was
120 min after the injection of the drug. Each animal served as its
own control and 20 s (for hot-plate), 10 s (for tail-immersion)
were used as a cut-off latency to avoid tissue damage. Test dura-
tion was 120 min for substances. Only the 4a group was observed
to 150 min since the activity was still continuing.
2-(Cyclohexylamino)-5-[((1-(2-hydroxyethyl)-3,5-
dimethylpyrazole-4-yl)azo)phenyl]-1,3,4-thiadiazole 3b
IR (KBr): 3248-3192 (O–H and N–H), 3065 (=C–H), 1559 (C=N),
1
1418 (N=N), 675 (C–S–C) cm–1. H-NMR d (ppm): 1.30–2.03 (m,
11H, cyclohexyl protons), 2.41 (s, 3H, pyrazole C5 methyl), 2.61 (s,
3H, pyrazole C3 methyl), 3.75 (q, 2H, –CH2CH2OH), 4.11 (t, 2H,
–CH2CH2OH), 4.32 (t, 1H, –CH2CH2OH), 7.81–7.95 (m, 4H, ArH),
8.70 (s, 1H, –NH-C6H11). MS (ES) [M+H]+: m/z 426.
2-[(2-Phenylethyl)amino]-5-[((1-(2-hydroxyethyl)-3,5-
dimethylpyrazole-4-yl)azo)phenyl]-1,3,4-thiadiazole 3c
IR (KBr): 3420 (O–H and N–H), 2925 (=C–H), 1576 (C=N), 1419
(N=N), 668 (C–S–C) cm–1. 1H-NMR d (ppm): 2.65 (s, 3H, pyrazole C5
methyl), 2.91 (s, 3H, pyrazole C3 methyl), 3.20 (t, 2H, –
CH2CH2C6H5), 3.88 (q, 2H, –CH2CH2OH), 3.99 (q, 2H, –CH2CH2C6H5),
4.30 (t, 2H, –CH2CH2OH), 4.52 (t, 1H, –CH2CH2OH), 7.46-8.20 (m,
9H, ArH), 10.70 (s, 1H, –NHCH2CH2C6H5). MS (ES) [M+H]+: m/z 448.
4-[((1-(2-Hydroxyethyl)-3,5-dimethylpyrazole-4-yl)-
azo)phenyl]-4-buthyl-2,4-dihydro-3H-1,2,4-triazole-3-
thione 4a
IR (KBr): 3423–3108 (O–H and N–H), 2919 (=C–H), 1623 (C=N),
1408 (N=N), 1243 (C=S) cm–1. 1H-NMR d (ppm): 0.78 (t, 3H, –
NHCH2CH2CH2CH3), 1.18 (m, 2H, –NHCH2CH2CH2CH3), 1.55 (m,
2H, –NCH2CH2CH2CH3), 2.42 (s, 3H, pyrazole C5 methyl), 2.62 (s,
3H, pyrazole C3 methyl), 3.75 (m, 4H, –NHCH2CH2CH2CH3 and –
CH2CH2OH), 4.11 (t, 2H, –CH2CH2OH), 4.95 (t, 1H, –CH2CH2OH),
7.83 (d, J= 8.5 Hz, 2H, ortho-protons to azo), 7.88 (d, J= 8.5 Hz, 2H,
meta-protons to azo), 13.99 (s, 1H, NH proton of triazole). MS (ES)
[M+H]+: m/z 400.
Statistics
4-[((1-(2-Hydroxyethyl)-3,5-dimethylpyrazole-4-
yl)azo)phenyl]-4-cyclohexyl-2,4-dihydro-3H-1,2,4-
Statistical analysis was carried out using GraphPad Prism 3.0
(GraphPad Software, San Diego, CA, USA). All data were
expressed as means € SEM. Groups of data for analgesia tests
were compared with an analysis of variance (ANOVA) of repeated
measures, followed by Tukey’s multiple comparison tests. Neu-
rological examination scores were compared with ANOVA test
followed by Tukey’s post-hoc test. Values of p a0.05 were
regarded as significant.
triazole-3-thione 4b
IR (KBr): 3155–3108 (O–H and N–H), 2927 (=C–H), 1628 (C=N),
1413 (N=N), 1243 (C=S) cm–1. 1H-NMR d (ppm): 1.19–2.68 (m, 17H,
cyclohexyl protons, pyrazole C5 methyl and pyrazole C3 methyl),
3.75 (q, 2H, –CH2CH2OH), 4.12 (t, 2H, –CH2CH2OH), 4.94 (t, 1H, –
CH2CH2OH), 7.69 (d, J= 8.3 Hz, 2H, ortho-protons to azo), 7.88 (d, J=
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