Abstract
Purpose : To develop some novel molecules effective against antibiotic-resistant bacterial infections. Methods : A series of azomethines (SB-1 to SB-6) were synthesized from β-phenyl acrolein moiety. The structures of the synthesized compounds were confirmed on the basis of their UV ultra-violet (UV) spectroscopy ( λmax : 200 - 400 nm), Fourier transform infra-red (FTIR, vibrational frequency: 500-4000 cm -1 ), 1 H nuclear magnetic resonance (NMR, chemical shift: 0 - 10 ppm), 13 C NMR (chemical shift: 0 - 200 ppm), mass spectrometry (m/z values: 0 - 500) and carbon hydrogen nitrogen (CHN) elemental analysis. The new compounds were screened for antibacterial activity by test-tube dilution and disc diffusion methods using gentamicin as reference standard. Results : The structures of azomethine were in full agreement with their spectral data. Among all the synthesized compounds, compounds SB-5 and SB-6 exhibited the highest minimum inhibitory concentration (MIC) of 62.5 μg/mL. At MIC of 250 μg/mL, all compounds SB-1 to SB-6 displayed significant antibacterial activity, compared to gentamycin (p < 0.05). SB-5 and SB-6 were active against S. aureus, P. aeruginosa and K. pneumoniae ; SB-3 was active against B. subtilis and S. aureus . SB-4 was active against P. aeruginosa and S. aureus while SB-1 and SB-2 were active against S. aureus . Conclusion : The synthesized compounds possess antibacterial activities compared to those of gentamycin. Keywords : Acrolein, Imines, Azomethine, Antibacterial, Gentamycin, Minimum inhibitory concentration
Highlights
Antimicrobial drugs occupy a unique niche in the history of medicine
The increased incidence of severe opportunistic bacterial infections in immunological deficient patients together with the development of resistance among pathogenic Gram-positive and Gram-negative bacteria have revealed great need to search for new compounds that are effective against antibioticresistant bacteria
Found C, 80.56; H, 5.78; N, 5.82 %; IR (KBr, cm-1): 3640 (Broad, O-H Str), 3055 (=C-H stretching of aromatic ring), 3038 (=C-H stretching of alkenyl group), 1668 (-C=N stretching azomethine group), 1540-1600 (C=C- stretching of aromatic ring), 1320 (C-N, stretching of azomethine group); 1H-NMR (500.1 MHz, CDCl3-d, δ/ppm): 5.4 (1H, s, -OH, D2O exchangeable), 5.72 (1H, t, J = 9.5 Hz, H-2'), 6.59 (1H, d,J = 12 Hz, H-3'), 7.4 - 7.8 (10H, m, phenyl), 8.29
Summary
Antimicrobial drugs occupy a unique niche in the history of medicine. The increased incidence of severe opportunistic bacterial infections in immunological deficient patients together with the development of resistance among pathogenic Gram-positive and Gram-negative bacteria have revealed great need to search for new compounds that are effective against antibioticresistant bacteria. Thereafter, the 16-h old broth cultures of the specified microorganisms were used for disc diffusion studies [13].The sample, control and standard treated discs were air-dried at room temperature, to remove any residual solvent which might interfere with the determination, sterilized and inoculated. These plates were initially placed at low temperature for 1 h to allow the maximum diffusion of compounds from the test disc into the agar plate and later incubated at 37 °C for 24 h in case bacteria [16], after which the zone of inhibition will be observed. Statistical analysis was performed using GraphPad Prism 5.0 and data analyzed using one-way analysis of variance (ANOVA) for comparison between groups followed by Dunnett's multiple comparison test at a significant level of p < 0.05
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