| Summary: | Synthesis and in-vitro test of antibacterial activity of some
chloropyrazoline derivatives from vanillin or veratraldehyde with pchloroacetophenone
was performed. The research was carried out through three
steps. The first step was synthesis of chalcone from veratraldehyde or vanillin
with p-chloroacetophenone to give chalcone 1a and 1b. The second step was
synthesis of pyrazoline from chalcone 1a and 1b with phenylhydrazine to give
pyrazoline 2a and 2b. The final step was in-vitro test of antibacterial activity of
pyrazolines 2a and 2b.
Synthesis of chalcone 1a was performed by stirring veratraldehyde,
p-chloroacetophenone and NaOH 30% (b/v) at room temperature for 4 h, while
chalcone 1b was performed by stirring vanillin, p-chloroacetophenone and NaOH
60% (b/v) at room temperature for 24 h. Synthesis of pyrazoline 2a and 2b were
performed by refluxing the chalcone 1a and 1b with phenylhydrazine in acidic
condition for 4 h. The structure of the synthesized compounds was confirmed by
FTIR, GC-MS and 1H and 13C-NMR spectrometers. The pyrazolines (2a and 2b)
were screened for antibacterial activity by agar well-diffusion against
Staphylococcus aureus, Bacillus cereus, Bacillus subtillis, Escherichia coli and
Shigella flexnerri
The result showed that chalcone 1a and 1b had been successfully
synthesized by the reaction of veratraldehyde or vanillin with pchloroacetophenone.
The yields were 79.07 and 59.22% respectively. Pyrazoline
2a and 2b had been synthesized from chalcone 1a or 1b with phenylhydrazine to
give 52.90 and 93.10% yield, respectively. Antibacterial screening showed that
both pyrazoline 2a and 2b were active against selected gram positive and negative
bacterial. Pyrazoline 2a was found to exhibits an antibacterial activity and its zone
of inhibition/concentration against Staphylococcus aureus (8.75/300), Bacillus
cereus (7.75/1000), Bacillus subtillis (6.50/1000), and Escherichia coli
(3.50/300). Pyrazoline 2b was found to exhibits an antibacterial activity and its
zone of inhibition/concentration against Staphylococcus aureus (4.75/100),
Bacillus cereus (2.50/500), Bacillus subtillis (4.50/300), Escherichia coli
(4.75/500) and Shigella flexnerri (3.75/300). The result showed that pyrazoline
derivatives which were subtituted with chloro, hydroxyl and methoxy, were able
to inhibit the growth of the tested pathogenic bacteria
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