3. FOOD ChEMISTRy & bIOTEChNOLOGy 3.1. Lectures

Chem. Listy, 102, s265–s1311 (2008) Food Chemistry & Biotechnology
Table I
The structures of the compounds studied
Compound R 1 R 2
1 nH 2 H
2 nH 2 C 6 H 5 –CH 2
3 nH 2 4–CH 3 –C 6 H 4 –CH 2
4 nH 2 4–Cl–C 6 H 4 –CH 2
5 nH 2 C 6 H 5 –CO
6 nH 2 4–CH 3 –C 6 H 4 –CO
7 nH 2 4–Cl–C 6 H 4 –CO
8 CH 3 H
9 CH 3 C 6 H 5 –CH 2
10 CH 3 4–CH 3 –C 6 H 4 –CH 2
11 CH 3 4–Cl–C 6 H 4 –CH 2
12 CH 3 C 6 H 5 –CO
13 CH 3 4–CH 3 –C 6 H 4 –CO
14 CH 3 4–Cl–C 6 H 4 –CO
nefelometer, was 1 × 10 7 CFU cm –3 . The 1 ml of this suspensions
was homogenized with 9 ml of melted (45 °C) Sabouraud
Dextrose Agar and poured into Petri dishes. On the surface of
the agar the 6 mm diameter sterile paper discs (Hi Media,
Mumbai, India) were put and impregnated with 10 –3 ml of
samples. The plates were incubated for 24–47 hours at 25 °C,
and the diameter of the resulting inhibition zone (including
the disc) was measured (in mm). The evaluation of antifungal
activities of samples was carried out in three repetitions.
Minimum inhibitory concentration (MIC) was determined
by the agar dilution method according to guidelines
established by the nCCLS standard M7-A5 25 . The MIC of
tested benzimidazoles is defined as the lowest concentration of
the compound at which no growth of the strain is observed in
time and under specified experimental conditions. Stock solutions
of the compounds were prepared in dimethylformamide
(DMF). Further dilutions were performed with distilled
water. The inoculated plates were then incubated at 35 °C
for 16–20 h. A control (using DMF without any test compound)
was included for each organism. It was determined
that the solvent had no activity against any of the test microorganisms.
The negative logarithms of molar MICs (log1/c MIC )
were determined and used for further calculations.
M o l e c u l a r M o d e l i n g a n d l o g P
C a l c u l a t i o n s
Molecular modeling studies were performed by using
CS Chem-Office Software version 7.0 (Cambridge software)
running on a P-III processor 26 . All molecules were
constructed by using Chem Draw Ultra 7.0 and saved as
the template structure. For every compound, the template
structure was suitably changed considering its structural
s754
features, copied to Chem 3D 7.0 to create a 3-D model and,
finally, the model was clened up and subjected to energy
minimization using molecular mechanics (MM2). The minimization
was executed until the root mean square (RMS)
gradient value reached a value smaller than 0.1 kcal mol –1 ⋅A.
The Austin Model-1 (AM-1) method was used for re-optimization
until the RMS gradient attained a value smaller
than 0.0001 kcal mol –1 ⋅A using MOPAC. The lowest energy
structure was used for each molecule to calculate lipophilicity
parameters (Table II).
S t a t i s t i c a l M e t h o d s
The complete regression analysis was carried out by
PASS 2005, GESS 2006, nCSS Statistical Softwares 27 .
Table II
Data of the lipophilicity parameters
Compound log P
1 0.99
2 2.96
3 3.44
4 3.52
5 2.84
6 3.32
7 3.39
8 1.48
9 3.45
10 3.94
11 4.01
12 3.33
13 3.81
14 3.89
Results
The results of antifungal studies of benzimidazoles
tested against Saccharomyces cerevisiae are summarized in
Table III. As indicated, all the compounds show antifungal
activities against the tested yeast. Consequently, compounds
with high log1/c MIC are the best antifungals. The MICs were
compared with Ketoconazole and Amphotericin which were
screened under similar conditions as reference drugs.
In order to identify the effect of lipophilicity on the
inhibitory activity, QSAR studies of title compounds were performed.
A set of benzimidazoles consisting of 14 molecules was
used for multilinear regression model generation. The reference
drugs were not included in model generation as they
belong to a different structural series. An attempt has been
made to find structural requirement for inhibition of Saccharomyces
cerevisiae using QSAR Hansch approach on benzimidazole
derivatives. To obtain the quantitative effects of the
lipophilicity parameter of benzimidazole derivatives on their
antifungal activity, QSAR analysis with log P was operated.