R.V. Satyendra et al. / European Journal of Medicinal Chemistry 46 (2011) 3078e3084
3081
Table 3
Anthelmintic activities of compounds.
Compounds/parameters
Concentration [%]
1
2
3
4
5a
5b
Albendazole
Paralytic time in (min)a
1%
2%
3%
1%
2%
3%
8.22 ꢁ 1.70
7.27 ꢁ 1.34
3.20 ꢁ 0.74
9.05 ꢁ 1.68
7.83 ꢁ 1.57
5.95 ꢁ 1.13
6.61 ꢁ 0.81
5.87 ꢁ 0.90
5.28 ꢁ 1.02
7.23 ꢁ 1.16
6.37 ꢁ 1.36
5.75 ꢁ 1.11
4.42 ꢁ 0.67
3.57 ꢁ 0.50
3.08 ꢁ 0.39
4.77 ꢁ 0.54
4.22 ꢁ 0.66
3.23 ꢁ 0.42
5.48 ꢁ 1.09
4.29 ꢁ 0.92
3.82 ꢁ 0.72
6.48 ꢁ 0.82
5.49 ꢁ 1.01
4.12 ꢁ 0.77
5.92 ꢁ 0.69
4.74 ꢁ 0.72
4.00 ꢁ 0.53
6.13 ꢁ 0.94
5.95 ꢁ 0.91
4.85 ꢁ 1.10
7.95 ꢁ 1.01
6.58 ꢁ 1.23
5.97 ꢁ 1.05
8.33 ꢁ 0.85
7.07 ꢁ 0.96
6.64 ꢁ 1.00
5.37 ꢁ 1.08
e
e
Death time in (min)a
7.20 ꢁ 1.95
e
e
a
Mean ꢁ SEM, n ¼ 6.
with the ligand obtained from PDB sum. For docking calculations,
Gasteigere-Marsili partial charges were assigned to the ligands and
nonpolar hydrogen atoms were merged. All torsions were allowed
to rotate during docking. The Lamarckian genetic algorithm and the
pseudo-Solis and Wets (pSW) methods were applied for minimi-
zation, using default parameters. Theoretically all the ligand
molecules showed encouraging binding energy. Among the six
4. Experimental
4.1. Chemistry
Melting points were recorded on electrothermal melting point
apparatus and are uncorrected. 1H and 13C NMR spectra were
recorded on Bruker 400 MHz spectrometer IISc, Bangalore, Karna-
molecules, docking of
b
-Tubulin with 3, 4 and 5a revealed that their
taka, India. Chemical shifts are shown in d values (ppm) with tet-
binding energy were ꢂ8.37 kJ molꢂ1
,
ꢂ7.05 kJ molꢂ1
ramethylsilane (TMS) as internal standard. LC-MS were obtained
using C 18 column on Shimadzu, LCMS 2010A, Japan. The FT-IR
spectra of compound were taken in KBr pellet (100 mg) using
Shimadzu Fourier transformed infrared (FT-IR) spectrophotometer.
and ꢂ7.22 kJ molꢂ1 respectively and it is considered as good
inhibitor of
b-Tubulin. In in vitro studies also 3, 4 and 5a has
emerged as active against P. posthuma. It can be predicted that the
activity may be due to inhibition of -Tubulin of helminths and
b
Column chromatography was performed using a silica gel
interfering with microtubule dynamics, consequently disturbing
microtubule-based processes.
(230e400 mesh). Elemental analysis was carried out using Vari-
oMICRO V1.7.0 (Elemental Analysersysteme GmbH). Silica gel
GF254 plates from Merck were used for TLC and spots located
either by UV, dipping in potassium permanganate solution.
The chemicals were purchased from SigmaeAldrich Co. and
solvents for column chromatography were of reagent grade and
were purchased from commercial source.
3. Conclusion
The data reported herein indicates that compound 3, 4 and 5a
has emerged as potentially active compounds as anthelmintic and
antioxidant compounds. These molecules have shown significant
results as compared to standard drug. In molecular docking studies
ligand molecules showed minimum binding energy and increased
affinity with the protein and it was found that hydrogen bond
formation with amino acid residues of active pocket may be
responsible for the anthelmintic activity as referred to Albendazole.
According to these results, we can conclude that compounds 3, 4
and 5a appears to be the most interesting compound among the
newly synthesized and seem potentially attractive as anthelmintic
drug.
4.1.1. 5,7-Dichloro-1,3-benzoxazole-2-thiol (1)
A mixture of 2-amino-4,6-dichlorophenol (0.1 mol), potassium
hydroxide (0.1 mol) and methanol (100 ml) was taken in a round
bottomed flask and carbon disulphide (0.1 mol) was added drop
wise to the mixture with constant stirring in ice cold condition.
Then the reaction mixture was refluxed for 8 h, poured onto
crushed ice and acidified with acetic acid (pH 6). The separated
product was filtered, dried and recrystallized from ethanol. The
structure was assigned to 5,7-dichloro-1,3-benzoxazole-2-thiol 1
by melting point and standard 1H NMR Data.
4.1.2. Ethyl [(5, 7-dichloro-1,3-benzoxazol-2-yl)sulfanyl]acetate (2)
Equimolar quantity of 5,7-dichloro-1,3-benzoxazole-2-thiol 1
(0.1 mol) and ethyl chloroacetate (0.1 mol) was taken in dry acetone
(40 ml) containing anhydrous potassium carbonate (5 g) and
refluxed on water bath for 10 h. Then the reaction mixture was
poured onto crushed ice, solid product thus obtained was filtered,
dried and recrystallized from ethanol. IR (KBr, nmax cmꢂ1): 1595
(C]N), 1737 (C]O). 1H NMR (CDCl3, 400 MHz):
d 7.77 (s, H, C-6),
7.61 (s, H, C-4), 4.31 (s, 2H, eSeCH2 proton), 4.16 (q, 2H, J ¼ 8 Hz,
CH2 protons of ester), 1.19 (t, 3H, J ¼ 8 Hz, eCH3). 13C NMR (CDCl3,
400 MHz):
d 167.94 (C]O), 163.16, 147.90, 143.91, 130.78, 124.96,
117.77, 116.16, 62.89 (OeCH2), 34.85 (SeCH2), 14.59 (CH3). MS
(LCMS): m/z 306 [Mþ], 308 [Mþ2], 310 [Mþ4].
4.1.3. 5,7-Dichloro-2-hydrazinyl-1,3-benzoxazole (3)
A mixture of ethyl [(5,7-dichloro-1,3-benzoxazol-2-yl)sulfanyl]
acetate 2 (0.1 mol) and hydrazine hydrate (0.2 mol) in methanol
(30 ml) was stirred for 30 min. The obtained solid was filtered,
dried and recrystallized from dimethyl formamide. IR (KBr,
nmax cmꢂ1): 1575 (C]N), 3356 (NeH). 1H NMR (DMSO, 400 MHz):
d
9.33 (s, 1H, NH, disappeared on D2O exchange), 7.29 (s, H, C-6),
Fig. 3. Structure of
b-Tubulin (PDB ID: 1OJ0).
7.17 (s, H, C-4), 4.68 (s, 2H, NH2, disappeared on D2O exchange). 13
C