Supramolecular Chemistry
6831
IR (KBr cm21): 943.3 (N–C–S str), 1278 (N–N–C
str), 3365(N–H str), 696.33 (C–S str), 3082 (Ar CHstr),
1446 (C–N str).
absorbance versus inverse concentration of b-cyclodex-
trin, using Benesi–Hilderband relation (22).
1=DA ¼ 1=D1 þ 1=K½Guestꢀo:½b 2 CDꢀ
1HNMR (ppm): 7.7 (m, 5H, Ar-H), 7.9 (s, 2H, NH2),
14.6 (s, 1H, S-H)
where DA is change in absorbance, De is change in
absorption coefficient, K stability constant, [Guest]o is the
concentration of compound and [b-CD] is the concen-
tration of b-cyclodextrin. The values of K for all the
complexes are calculated using the relation
K ¼ Intercept/Slope
Step-4: synthesis of 4-arylidenamino amino-5-phenyl-
4H-1,2,4-triazole-3-thiol (Compound-4, A–D)
An aromatic aldehyde (2.0 mmol) was dissolved in glacial
acetic acid (4.0 mL) and compound-3 (0.38 g, 2.0 mmol)
was added to it. The reaction mixture was refluxed for
10 minutes. Then the mixture was cooled. The solid mass
formed was separated by filtration, washed with ethanol
and dried to give 4-arylidenamino amino-5-phenyl-4H-
1,2,4-triazole-3-thiol. By following the same procedure,
four different 4-arylidenaminoamino-5-phenyl-4H-1,2,4-
triazole-3-thiol (A, B, C and D) were prepared
corresponding to four different aromatic aldehydes
(benzaldehyde, 4-methoxybenzaldehyde, cinnamaldehyde
and furfural).
The value of DG at 298 K was calculated using the
equation:
DG ¼ 2RT ln K
Evaluation of antibacterial activity
The antibacterial activity of compounds was studied as per
cup-plate method (23, 24). The solutions of the test
compounds were prepared in dimethyl sulphoxide
(DMSO) at 500 mg/mL. The bacterial strains of Escher-
ichia coli (MTCC 40), Bacillus subtilis (MTCC 441),
Staphylococcus aurous (MTCC 87) and Proteus vulgaris
(MTCC 426) were inoculated into 100 ml of the sterile
nutrient broth and incubated at 37 ^ 18C for 24 h. The
density of the bacterial suspension was standardised by
McFarland method. Wells of uniform diameter (6 mm)
were made on agar plates, after inoculating them
separately with the test organisms aseptically. The drug
(500 mg/mL) and the test compounds (500 mg/mL) were
introduced with the help of micro pipette, and the plates
were placed in the refrigerator at 8–108C for proper
diffusion of drug into the media. After two hours of cold
incubation, the petri plates were transferred to incubator
and maintained at 37 ^ 28C for 18–24 h. Then, the petri
plates were observed for zone of inhibition by using venire
scale. The results were reported by comparing the zone of
inhibition shown by the test compounds with standard drug
(Tetracycline).
Phase solubility measurements
The aqueous phase solubility of the compounds at various
concentrations of b–cyclodextrin (0–10 mM) was studied
by Higuchi–Conners method (20). A rotary flash shaker
was used to shake the accurately weighed sample of these
compounds, with various concentrations of b-cyclodextrin
(0–10 mM) at room temperature in different conical flasks
for a period of 48 hours till the attainment of equilibrium.
Whatmann-42 filter papers were used to filter the solution.
These solutions were analysed by a UV-Visible spectro-
photometer. The various values of absorbance at l-max
were plotted against different concentrations of b-
cyclodextrin.
Preparation of inclusion complexes
Co-precipitation method was used for the preparation of
inclusion complexes of the compounds with b-cyclodex-
trin (18, 21). Proper concentrations of the solutions
containing these compounds were added drop wise to the
solution of b-cyclodextrin in the required concentration
(1:5). Stirring of the solutions was carried out for a period
of 48 h. Then the solutions were filtered. The filtrates were
cooled in refrigerator for 24 h. The precipitates formed
were filtered and dried.
Evaluation of antioxidant activity
In the present study, DPPH (2, 2-diphenyl-1-picrylhy-
drazyl) scavenging assay method was used for screening
the antioxidant activity of the synthesised compounds as
suggested by Tagashira and Ohtake (25). 0.1 mM solution
of DPPH in methanol was prepared and 1 ml of this
solution was mixed with 3 ml of sample solutions in water
at different concentrations. Finally, after 30 min of
incubation period at room temperature, the absorbance
was measured at 517 nm against a blank. Decreasing of the
DPPH solution absorbance indicated an increase of the
DPPH radical-scavenging activity. DPPH radical-scaven-
ging activity was calculated according to the following
Study of thermodynamic properties
The stability constants of the inclusion complexes (K)
were calculated from plot of inverse of change in