Macrolide and ketolide antibiotic separation by reversed phase high performance liquid chromatography

Isolation of two Pseudomonas strains producing pseudomonic acid A

Two novel Pseudomonas strains were isolated from groundwater sediment samples. The strains showed resistance against the antibiotics tetracycline, cephalothin, nisin, vancomycin, nalidixic acid, erythromycin, lincomycin, and penicillin and grew at temperatures between 15 and 37 degrees C and pH values from 4 to 10 with a maximum at pH 7 to 10. The 16S ribosomal RNA gene sequences and the substrate spectrum of the isolates revealed that the two strains belonged to the Pseudomonas fluorescens group. The supernatants of both strains had an antibiotic effect against Gram-positive bacteria and one Gram-negative strain. The effective substance was produced under standard cultivation conditions without special inducer molecules or special medium composition. The antibiotically active compound was identified as pseudomonic acid A by off-line high performance liquid chromatography (HPLC) and Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS). The measurement on ultra performance liquid chromatography (UPLC, UV-vis detection) confirmed the determination of pseudomonic acid A which was produced by both strains at 1.7-3.5mg/l. Our findings indicate that the ability to produce the antibiotic pseudomonic acid A (Mupirocin) is more spread among the pseudomonads then anticipated from the only producer known so far.

Simultaneous determination of erythromycin ethylsuccinate and its metabolite erythromycin in human plasma using liquid chromatography–electrospray ionization mass spectrometry for clinical study

A sensitive and selective liquid chromatography-electrospray ionization mass spectrometry (LC-ESI-MS) method was developed for simultaneous identification and quantification of erythromycin ethylsuccinate and erythromycin in human plasma, which can be well applied to clinical study. The method was based on liquid-liquid extraction, followed by a LC procedure with an ODS C18 column, and mixture of acetonitrile and 1.67 mmol/l acetic acid as mobile phase. MS detection was performed using a single quadrupole mass spectrometer in positive selected ion monitoring (SIM) mode. The method was validated to be linear, precise and accurate. The lower limit of quantification of erythromycin ethylsuccinate and erythromycin were both 0.5 ng/ml. The proposed method enables the unambiguous identification and quantification of erythromycin ethylsuccinate and erythromycin for clinical drug monitoring.

A computational approach to the synthesis of dirithromycin

Dirithromycin is a macrolide antibiotic derived from erythromycin A. Dirithromycin is synthesized by the condensation of 9(S)-erythromycylamine with 2-(2-methoxyethoxy)-acetaldehyde. To gain insight into the synthesis, the condensation mechanism has been analyzed computationally by the AM1 method in the gas phase. First, the formation of the Schiff bases of dirithromycin and epidirithromycin from 9(S)-erythromycylamine and 2-(2-methoxyethoxy)-acetaldehyde were modeled. Then, the tautomerization of the Schiff bases to dirithromycin and epidirithromycin were considered. Finally, the epimerization of the Schiff base of epidirithromycin to the Schiff base of dirithromycin was investigated. Our results show that, even though carbinolamine forms faster for epidirithromycin than the corresponding structure for dirithromycin, dirithromycin is the major product of the synthesis.

HPLC separation of antibiotics present in formulated and unformulated samples

Analysis of antibiotics in formulated and unformulated samples demand a highly specific and rapid method as many antibiotics (e.g. beta-lactams) have serious stability problems. HPLC techniques can provide a valuable tool for generating highly pure preparations for characterizing the antimicrobial activities. In the present review article, column and mobile phase conditions for the various classes of antibiotics viz. penicillins, cephalosporins, macrolides, tetracyclines, aminoglycosides, quinolones, rifamycins etc. have been presented from April 1998 to November 2000. A brief discussion on chemical structure, spectrum of activity and action mechanism of each class has also been given.

Study on the electrochemical detection of the macrolide antibiotics clarithromycin and roxithromycin in reversed-phase high-performance liquid chromatography

The optimal conditions of the amperometric detection of the macrolide antibiotics clarithromycin and roxithromycin were found by cyclic voltammetric studies and HPLC-electrochemical detection responses obtained in different temperatures (25.5-60 degrees C) and different but almost isoelutropic binary, ternary and quaternary mixtures of aqueous buffer (pH 7), methanol, acetonitrile and isopropanol. These conditions were also proved to be applicable for the quantitative detection of clarithromycin in human plasma using roxithromycin as an internal standard and vice versa. It was demonstrated that increased attention has to be paid to eluent composition and column temperature to ensure sensitive and reproducible electrochemical responses as well as regularly shaped peaks for both macrolides tested.