842
K. SINGH ET AL.
TABLE 7
Minimum bactericidal concentrations (MBC) of compound
Microbial strains
Compound Bacilus subtilis B. megaterium Escherichia coli Saccharomyces cerevisiae
HL4
>128
>128
128
128
HL1: 2-Chloro-5-nitrobenzylidene-o-aminothiophenol
HL2: 3-Bromobenzylidene-o-aminothiophenol
HL3: 4-Methylbenzylidene-o-aminothiophenol
HL4: 2-Chlorobenzylidene-o-aminothiophenol
Me2Si(L4)Cl showed almost same antimicrobial activity against
Escherichia coli (12 mm), Bacillus megaterium (10 mm), and
Saccharomyces cerevisiae (12 mm). The results implicate that
Pseudomonas aeruginosa and Candida albicans were resistant
to all the compounds evaluated in this experiment.
The MIC against B. subtilis and B. megaterium was
128µg/mL and 64 µg/mL against E. coli and S. cerevisiae.
The MBC was greater than 128 µg/mL against B. subtilis and
B. megaterium and 128 µg/mL against E. coli and S. cerevisiae.
Compound HL4 showed maximum activity in terms of zones of
growth inhibition as compared to other compounds screened in
this test. Hence, after testing in vivo compound HL4 may be used
in food and pharmaceutical industries as it inhibits Escherichia
coli, Bacillus megaterium, B. subtilis, and Staphylococcus au-
reus, which are food borne in nature and the organisms Pseu-
domonas aeruginosa, Saccharomyces cerevisiae, and Candida
albicans, which are harmful human pathogens.
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The antibacterial results evidently showed that the activities
of the ligands became more pronounced and significant when
coordinated to the metal ions. It has been suggested that coor-
dination reduces the polarity of the metal ion mainly because
of partial sharing of its positive charge with donor group within
the whole chelate ring system. This process of chelation thus
increases the lipophilic nature of the central metal atom, which
in turn, favors its permeation through the lipoid layer of the
membrane thus causing the metal complex to cross the bacte-
rial membrane more effectively and increasing the activity of
the complexes. Besides from this, many other factors, such as
solubility and dipole moment, conductivity influenced by metal
ion may be possible reasons for remarkable antibacterial ac-
tivities of these complexes.[27] It also has been observed that
some moieties, such as azomethine linkage or heteroaromatic
nucleus, introduced into such compounds exhibit extensive bi-
ological activities that may be responsible for the increase in
hydrophobic character and liposolubility of the molecules in
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