Synthesis and antibacterial profile of novel azomethine derivatives of β-phenylacrolein moiety

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), 1H nuclear magnetic resonance (NMR, chemical shift: 0 - 10 ppm), 13C 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.

3-Dichloroacetyl oxazolidine protect maize from imazethapyr herbicide injury

Safeners are an important tool used to ensure the safe using of herbicide. The objective of this paper was to investigate the protective effect of four 3-dichloroacetyl oxazolidine safeners (3-dichloroacetyl-2,2-dimethyl-1,3-oxazolidine [R-28725], racemate of 3-dichloroacetyl-2,2-dimethyl-4- ethyl-1,3-oxazolidine, and its two chiral stereoisomers) in reducing the injury caused by imazethapyr. Physiological and biochemical tests were conducted under laboratory condition, by using seed treatment with safeners and soil treatment with imazethapyr, respectively. The interaction of two safeners (R-28725 and R-stereoisomer) and imazethapyr reduced the injury of maize significantly, and also increased glutathione content, activity of glutathione S-transferases, and activity of acetolactate synthase in maize. When induced by R-stereoisomer, the GSH content in root and in shoot increased 100.7% and 73.6%, respectively. When induced by R-28725, the GST activity in vivo increased threefold and the GST activity in vitro more than doubled. The kinetic parameter Vmax of GST in the maize treated with R-28725 and R-stereoisomer increased by 102.2% and 81.9%, respectively, compared with the control. The results also showed that R-28725 and R-stereoisomer induced glutathione S-transferases affinity for the substrate of conjugation reaction significantly.

The whole-cell immobilization of D-hydantoinase-engineered Escherichia coli for D-CpHPG biosynthesis

Background: D-Hydroxyphenylglycine is considered to be an important chiral molecular building-block of antibiotic reagents such as pesticides, and β-lactam antibiotics. The process of its production is catalyzed by D-hydantoinase and D-carbamoylase in a two-step enzyme reaction. How to enhance the catalytic potential of the two enzymes is valuable for industrial application. In this investigation, an Escherichia coli strain genetically engineered with D-hydantoinase was immobilized by calcium alginate with certain adjuncts to evaluate the optimal condition for the biosynthesis of D-carbamoyl-p-hydroxyphenylglycine (D-CpHPG), the compound further be converted to D-hydroxyphenylglycine (D-HPG) by carbamoylase. Result: The optimal medium to produce D-CpHPG by whole-cell immobilization was a modified Luria-Bertani (LB) added with 3.0% (W/V) alginate, 1.5% (W/V) diatomite, 0.05% (W/V) CaCl2 and 1.00 mM MnCl2. The optimized diameter of immobilized beads for the whole-cell biosynthesis here was 2.60 mm. The maximized production rates of D-CpHPG were up to 76%, and the immobilized beads could be reused for 12 batches. Conclusions: This investigation not only provides an effective procedure for biological production of D-CpHPG, but gives an insight into the whole-cell immobilization technology. © 2016 Pontificia Universidad Católica de Valparaíso. Production and hosting by Elsevier B.V. All rights reserved.