Characterization of phosphonomycin by microchromatographic and related techniques

Fosfomycin determination in serum by capillary zone electrophoresis with indirect ultraviolet detection

Capillary zone electrophoresis with indirect ultraviolet detection was used for the determination of fosfomycin in serum. Running buffer consisted of a mixture of 200 mM sodium borate with 10 mM phenylphosphonic acid used as ultraviolet absorbing background electrolyte. Relationships between the pH of the buffer and the efficiency of the separation (migration times and selectivities) or the sensitivity of detection were investigated. The method was then validated over a 10-100 micrograms ml-1 concentration range to be applied to further therapeutic drug monitoring. The choice of ethylphosphonic acid as internal standard is discussed. The specificity and the linearity of the technique are demonstrated. The inter-day precision was satisfactory with a relative standard deviation of less than 2%. Accuracy was calculated with a standard error near 0.5 and 18% for 100 and 10 micrograms ml-1, respectively.

Biosynthesis of fosfomycin by Streptomyces fradiae

The antibiotic fosfomycin was produced as a secondary metabolite in a glucose-asparagine medium containing citrate, l-methionine, and l-glutamate. The citrate requirement for antibiotic synthesis was related to its requirement for growth. In contrast, l-methionine and l-glutamate caused a marked stimulation of fosfomycin production and had no effect on growth. l-Methionine had to be added early to effect maximal antibiotic synthesis later in the fermentation. The l-glutamate requirement was not specific, since several tricarboxylic acid cycle intermediates could replace this amino acid. l-Asparagine was the most effective nitrogen source for growth and production of fosfomycin. Glycine, an alternate nitrogen source, supported fosfomycin synthesis only when added in excess of that needed for growth. Cobalt and inorganic phosphate were required also for antibiotic production at concentrations exceeding those supporting maximal growth. Radioactive incorporation studies showed that the methyl carbon of methionine was the precursor of the methyl of fosfomycin. Carbon 1 of fosfomycin was derived from glucose carbons 1 and 6, whereas glucose-2-(14)C labeled fosfomycin carbon 2. Radioactivity from acetate-2-(14)C was distributed equally between fosfomycin carbons 1 and 2. No incorporation of acetate-1-(14)C, asparagine-U-(14)C, citrate-1,5-(14)C, or glutamate-U-(14)C occurred. The labeling pattern of fosfomycin carbons 1 and 2 was similar to that found in 2-aminoethylphosphonate from Tetrahymena.

Microbial epoxidation of cis-propenylphosphonic to (-)-cis-1,2-epoxypropylphosphonic acid

Eighteen species of Penicillium, one of Oidium and one of Paecilomyces were found to effect a stereospecific conversion of cis-propenylphosphonate to fosfomycin which was identified by paper chromatography and gas-liquid chromatography (GLC) of the trimethylsilyl esters. Penicillium spinulosum carried out the epoxidation only after the glucose substrate had been utilized. Glucose controlled the epoxidation since its residual concentrations in the broth severely depresses the reaction. At optimum levels of glucose, an epoxidation efficiency approaching 90% of olefin charged (0.2 g/liter) was obtained after 10 days of incubation. The olefin concentration could be increased to 0.5 g/liter when glucose was replaced by glycerol, whereby a 90% conversion to fosfomycin was attainable in 6 days. The high conversion efficiency, a good agreement between the GLC assay and bioactivity, are indicative of the levorotatory nature of the product.