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Bangladesh J Pharmacol 2016; 11: 67-74
12.5 and 25 µM concentrations, respectively. The
commercially available lyophilized streptokinase vial
(1,500,000 IU) was diluted with PBS and mixed
properly. From which streptokinase equivalent to
30,000 IU was used as a standard to observe the
thrombolytic activity.
cellular plasma membrane.
Most of the clinical available drugs have Log S higher
than -4.00. The compounds exhibited a Log S value
greater than -4.00, ranging between -0.81 and -3.78
(except compound 4c). A positive value for drug-
likeness indicates that the compound contains predomi-
nantly fragments that are often present in most
currently available drugs. Only compound 4c, the 3,5-
dinitrophenyl derivative was an exception in the in
silico studies as it was exhibiting a TPSA value of 171 Å,
Log S value of -4.24 and one Lipinski violation.
Whole blood was collected and 500 μL of blood was
transferred to each of the previously weighed micro-
centrifuge tubes and incubated at 37°C for 45 min for
clot formation. After clot formation, serum was
completely removed (aspirated out without disturbing
the clot formed) and each tube with the clot was again
weighed to determine the clot weight. 100 μL of diluted
test compounds (6.25, 12.5 and 25 µM) for screening
were added to the labeled microcentrifuge tube
containing clot. 100 μL of streptokinase (30,000 IU) was
added as the positive thrombolytic control and 100 μL
of PBS as the negative thrombolytic control was
employed. All the tubes were then again incubated at
37°C for 90 min and observed for clot lysis. After incu-
bation, fluid obtained was removed and tubes were
again weighed to observe the difference in weight after
clot disruption. Difference obtained in weight taken
before and after clot lysis was expressed as percentage
of clot lysis. The percent clot lysis was calculated
according to the following formula:
The drug score combines drug-likeness, lipophilicity,
solubility, molecular weight and the risk of toxicity into
a single numerical value that can be used to predict a
global value for each compound as a potential new
drug candidate, a positive value of drug scores indicate
that the molecules contain predominant pharmaco-
phoric groups, which are often found in pharmaceu-
ticals.
The results from the calculations show that the com-
pounds gave values for drug-likeness between -8.39 to
2.7. All compounds showed positive values in the drug
score calculation, the values ranged from 0.37 to 0.91.
The results highlights that the designed 1,3,4-oxadia-
zole have potential as new drug candidates. Table II
represents the calculated %ABS, TPSA and Lipinski
parameters of the synthesized compounds.
Molecular docking results
Statistical analysis
The docking study of the 1,3,4-oxadiazoles onto the
active site of the enzyme factor Xa (1NFY) were
significant, as all the eleven 1,3,4-oxadiazoles were
exhibiting significantly higher docking score and consi-
derable lower crash score in comparison to the co-
crystallized ligand. The ligand, RPR132747 exhibited a
docking and crash score of 6.2033 and -2.2025 Kcal/M
respectively, with the main hydrophobic interactions
with the surrounding residues Cys191, Gly216, Ala190
and Trp215, strongly contributed to the stabilization.
The hydrogen and the nitrogen of the imine function
exhibited hydrogen bond interaction with the residues
Cys191.H and Cys191.O at a distance of 2.887 and 1.988
Å, respectively. The proton of the amino group exhibi-
ted hydrogen bond interaction with the residue Trp215
at a distance of 2.512 Å. The oxygen of the keto function
of piperazin-2-one moiety exhibited hydrogen bond
interaction with the residue Gly218 at a distance of
2.617 Å. None of the compounds exhibited crash score
of greater than -4.5 Kcal/M. A crash score greater than -
4.5 Kcal/M, indicates inappropriate penetration of the
ligand into the binding site of 1CQE resulting in the
decreased forces of interaction with the amino acid.
The mean clot lysis percentage of test compounds in
different concentrations was compared with the stan-
dard streptokinase and phosphate buffered saline using
the repeated measures ANOVA with Dunnet’s test.
Mean, standard error of mean (SEM) calculations and
ANOVA test were performed using ‘‘GraphPad Prism
version 4.0’’ software. The data obtained is expressed as
mean ± SEM. The concentration which produced clot
lysis half maximally (EC50) was also determined
graphically from the percentage of clot lysis at various
concentrations of the test compound.
Results
In silico ADME results
Molecular weight of each ligand was within the range
of 229 to 395 D. They also had moderate to high
predicted oral availability based on %ABS ranging
between 50 to 82%.
Generally, a compound needs a score less than 5 for
lipophilicity, the lipophilicity data suggested that the
compounds were optimally lipophilic in nature ranging
from -0.47 to 1.92. All the compounds (except com-
pound 4c) also showed a TPSA of less than 140 Å,
indicating a good permeability of the drug in the
The docking study revealed that the 1,3,4-oxadiazole
derivatives, possessed high affinity towards 1NFY
(Figure 3). The 1,3,4-oxadiazoles derived from benzimi-