The trisubstituted enolate- and C–C bond-forming capacities of engineered carboxymethylproline synthases CMPSs are coupled with the malonyl-CoA synthetase MatB to enable stereoselective preparation of 5- and 6-membered N-heterocycles functionalised with alkyl-substituted carboxymethyl side chains, starting from achiral alkyl-substituted malonic acids and L-amino acid semialdehydes. The results illustrate the biocatalytic utility of crotonases in tandem enzyme-catalysed reactions for stereoselective synthesis.

The beta-lactam antibiotics and related -lactamase inhibitors are amongst the most important small molecules in clinical use. Most, but not all, -lactams including penicillins, cephalosporins, and clavulanic acid are produced via fermentation or via modification of fermented intermediates, with important exceptions being the carbapenems and aztreonam. The desire for more efficient routes to existing antibiotics and for access to new and synthetically challenging ones stimulates continued interest in -lactam biosynthesis. We review knowledge of the pathways leading to -lactam antibiotics focusing on the mechanisms, structures and biocatalytic applications of the enzymes involved.

A new, simple, rapid and sensitive batch chemiluminescence (CL) method for determination of six fluoroquinolones (ciprofloxacin, gatifloxacin, levofloxacin, lomefloxacin HCl, ofloxacin and sparfloxacin) is proposd. The method is based on the CL generated during the oxidation of luminol by N-bromosuccinimide (NBS) in alkaline medium. The determination of the studied drugs is based on their inhibiting effect on the emission intensity of NBS-luminol chemiluminescent reaction. The effect of analytical variables on this CL system is discussed. The study was validated according to ICH guidelines. Under the optimum experimental conditions, the linear range is 50 to 400 ng/ml for ciprofloxacin, 50 to 600 ng/ml for gatifloxacin, lomefloxacin HCl and sparfloxacin and 25 to 400 ng/ml for levofloxacin and ofloxacin and the detection and quantitation limits for the studied drugs were not more than 4.88 and 14.80 ng/ml, respectively. The proposed method has been applied to detect the studied drugs in their pure forms and in different pharmaceutical formulations. The possible mechanism of the CL reaction was discussed.

A new, simple, rapid and sensitive batch chemiluminescence (CL) method for determination of six fluoroquinolones (ciprofloxacin, gatifloxacin, levofloxacin, lomefloxacin HCl, ofloxacin and sparfloxacin) is proposd. The method is based on the CL generated during the oxidation of luminol by N-bromosuccinimide (NBS) in alkaline medium. The determination of the studied drugs is based on their inhibiting effect on the emission intensity of NBS-luminol chemiluminescent reaction. The effect of analytical variables on this CL system is discussed. The study was validated according to ICH guidelines. Under the optimum experimental conditions, the linear range is 50 to 400 ng/ml for ciprofloxacin, 50 to 600 ng/ml for gatifloxacin, lomefloxacin HCl and sparfloxacin and 25 to 400 ng/ml for levofloxacin and ofloxacin and the detection and quantitation limits for the studied drugs were not more than 4.88 and 14.80 ng/ml, respectively. The proposed method has been applied to detect the studied drugs in their pure forms and in different pharmaceutical formulations. The possible mechanism of the CL reaction was discussed.

A new, simple, rapid and sensitive batch chemiluminescence (CL) method for determination of six fluoroquinolones (ciprofloxacin, gatifloxacin, levofloxacin, lomefloxacin HCl, ofloxacin and sparfloxacin) is proposd. The method is based on the CL generated during the oxidation of luminol by N-bromosuccinimide (NBS) in alkaline medium. The determination of the studied drugs is based on their inhibiting effect on the emission intensity of NBS-luminol chemiluminescent reaction. The effect of analytical variables on this CL system is discussed. The study was validated according to ICH guidelines. Under the optimum experimental conditions, the linear range is 50 to 400 ng/ml for ciprofloxacin, 50 to 600 ng/ml for gatifloxacin, lomefloxacin HCl and sparfloxacin and 25 to 400 ng/ml for levofloxacin and ofloxacin and the detection and quantitation limits for the studied drugs were not more than 4.88 and 14.80 ng/ml, respectively. The proposed method has been applied to detect the studied drugs in their pure forms and in different pharmaceutical formulations. The possible mechanism of the CL reaction was discussed.

A new, simple, rapid and sensitive batch chemiluminescence (CL) method for determination of six fluoroquinolones (ciprofloxacin, gatifloxacin, levofloxacin, lomefloxacin HCl, ofloxacin and sparfloxacin) is proposd. The method is based on the CL generated during the oxidation of luminol by N-bromosuccinimide (NBS) in alkaline medium. The determination of the studied drugs is based on their inhibiting effect on the emission intensity of NBS-luminol chemiluminescent reaction. The effect of analytical variables on this CL system is discussed. The study was validated according to ICH guidelines. Under the optimum experimental conditions, the linear range is 50 to 400 ng/ml for ciprofloxacin, 50 to 600 ng/ml for gatifloxacin, lomefloxacin HCl and sparfloxacin and 25 to 400 ng/ml for levofloxacin and ofloxacin and the detection and quantitation limits for the studied drugs were not more than 4.88 and 14.80 ng/ml, respectively. The proposed method has been applied to detect the studied drugs in their pure forms and in different pharmaceutical formulations. The possible mechanism of the CL reaction was discussed.

This study describes, for the first, the development and validation of a novel high-throughput micorwell spectrophotometric assay for determination of the quinolone antibiotic rosoxacin (ROS) in its bulk and capsules. The assay involved the reaction between ROS and sodium nitroprusside (SNP) forming a red-colored product exhibiting maximum absorption peak (λmax) at 455 nm. The reaction was carried out in 96-microwell plate and the absorbance of the colored-product was measured by microwell plate absorbance reader at 455 nm. The variables affecting the reaction were carefully investigated using the microwell format and the optimum conditions under were established. Under the optimized conditions, a linear relationship with good correlation coefficient (0.9992) was found between the absorbance of the ROS-SNP chromogen and ROS concentration in the range of 15-150 μg/mL. The limits of detection and quantification were 3.5 and 11.6 μg/mL, respectively. The assay showed high precision as the values of relative standard deviations (RSD) did not exceed 2%. The proposed assay was successfully applied to the determination of ROS in its capsules; the label claim percentages were 102.81±1.43%. The results were compared favorably with those of a reference pre-validated method. The proposed assay is practical and valuable in terms of its routine application in determination of ROS in its bulk and capsules in pharmaceutical quality control laboratories.

This study describes, for the first, the development and validation of a novel high-throughput micorwell spectrophotometric assay for determination of the quinolone antibiotic rosoxacin (ROS) in its bulk and capsules. The assay involved the reaction between ROS and sodium nitroprusside (SNP) forming a red-colored product exhibiting maximum absorption peak (λmax) at 455 nm. The reaction was carried out in 96-microwell plate and the absorbance of the colored-product was measured by microwell plate absorbance reader at 455 nm. The variables affecting the reaction were carefully investigated using the microwell format and the optimum conditions under were established. Under the optimized conditions, a linear relationship with good correlation coefficient (0.9992) was found between the absorbance of the ROS-SNP chromogen and ROS concentration in the range of 15-150 μg/mL. The limits of detection and quantification were 3.5 and 11.6 μg/mL, respectively. The assay showed high precision as the values of relative standard deviations (RSD) did not exceed 2%. The proposed assay was successfully applied to the determination of ROS in its capsules; the label claim percentages were 102.81±1.43%. The results were compared favorably with those of a reference pre-validated method. The proposed assay is practical and valuable in terms of its routine application in determination of ROS in its bulk and capsules in pharmaceutical quality control laboratories.

This study describes, for the first, the development and validation of a novel high-throughput micorwell spectrophotometric assay for determination of the quinolone antibiotic rosoxacin (ROS) in its bulk and capsules. The assay involved the reaction between ROS and sodium nitroprusside (SNP) forming a red-colored product exhibiting maximum absorption peak (λmax) at 455 nm. The reaction was carried out in 96-microwell plate and the absorbance of the colored-product was measured by microwell plate absorbance reader at 455 nm. The variables affecting the reaction were carefully investigated using the microwell format and the optimum conditions under were established. Under the optimized conditions, a linear relationship with good correlation coefficient (0.9992) was found between the absorbance of the ROS-SNP chromogen and ROS concentration in the range of 15-150 μg/mL. The limits of detection and quantification were 3.5 and 11.6 μg/mL, respectively. The assay showed high precision as the values of relative standard deviations (RSD) did not exceed 2%. The proposed assay was successfully applied to the determination of ROS in its capsules; the label claim percentages were 102.81±1.43%. The results were compared favorably with those of a reference pre-validated method. The proposed assay is practical and valuable in terms of its routine application in determination of ROS in its bulk and capsules in pharmaceutical quality control laboratories.

The kinetics and mechanism of hexacholroiridate(IV) oxidation of carboxymethyl cellulose (CMC) in aqueous solutions at a constant ionic strength of 0.1 mol dm−3 has been investigated spectrophotometrically. The experimental results showed first-order dependence in [IrCl6]2− and fractional first-order kinetics with respect to CMC concentration. An inversefractional first-order in [H+] was observed. A kinetic evidence for the formation of 1:1 intermediate complex was revealed. The reaction kinetics seems to be of considerable complexity where one chloride ion from hexacholoiridate(IV) oxidant may act as a bridging ligand between the oxidant and the substrate into the formed intermediate complex. The ionic strength was found to have a negligible influence on the reaction rates. The kinetic parameters have been evaluated, and a tentative reaction mechanism consistent with the kinetic results is discussed.