Erythromycin analysis

Erythromycins. Erythromycin A (14, R = OH, R = CH3, R" = H), the most widely used macroHde antibiotic, was the principal product found in culture broths of Streptomjces eTythreus (39), now reclassified as Saccharopoljspora eythraea (40). It contains a highly substituted aglycone, erythronoHde A, (16, R = R = OH) to which desosamine (1, R = OH, R = H) and cladinose (8, R = CH ) are attached (41). The complete stereochemistry of erythromycin A was estabUshed by x-ray analysis of its hydroiodide dihydrate (42) total synthesis of erythromycin A was a landmark achievement (43), a task previously considered hopeless (44). 

Of the latter four agents, clindamycin has the most data supporting its use. However, the clinician must be aware of inducible clindamycin resistance. For CA-MRSA isolates determined to be resistant to erythromycin but sensitive to clindamycin, an additional laboratory analysis, known as the erythromycin-clindamycin D-zone test, is conducted to assess for inducible clindamycin resistance.15 Isolates for which the D-zone test indicates inducible resistance should not be treated with clindamycin. 

In addition, because it is used for the industrial-scale production of erythromycin A, the genome of Sacchropolyspora erythraea has been recently sequenced. Analysis of the genome sequence will provide further insight into rational for developing strains with improved yields of antibiotics [53]. 

Cash P et al. A proteomic analysis of erythromycin resistance in Streptococcus pneumoniae. Electrophoresis 1999 20 2259-2268. 

The aglycone part of erythromycin A (lb) can be considered as pseudosym-metric (i.e., the stereochemistry of fragment C-4 to C-6 and that of C-10 to C-12 can be regarded as the same). Retro synthetic analysis suggests that the... 

Scheme 7-1. Retro synthetic analysis of the aglycone of erythromycin A (la).

Several common methods for the detection of these compounds in environmental media have been proposed such as microbiological assay and conventional chromatographic methods. However, only one example of the application of immunochemical methods to the analysis of environmental samples has been reported [84]. In this case, erythromycin could be measured at concentrations higher than 10 pg L 1 using the Charm II6600/7600 assay in water samples proximal to livestock farms. 

Erythromycin, a macrolide antibiotic, lacks a significant chromophore. Detection sensitivity was enhanced by using a wavelength of 200 nm and selecting an injection solvent of lower conductivity than the BGE. In order to facilitate the separation of erythromycin and its related substances, 35% (v/v) ethanol was incorporated into a 150 mM phosphate buffer pH 7.5. Resolution of all of the compounds was achieved in approximately 45 min. The method was employed as an assay method for erythromycin and for impurity determination. Peptide antibiotics, such as colistin and polymyxin, are mixtures of many closely related compounds. A validated CZE method for impurity analysis of polymyxin B was described, employing 130 mM triethanolamine-phosphate buffer at pH 2.5 to reduce the adsorption of analyte onto the capillary wall. Methyl-/l-cyclodextrin (M-/1-CD) and 2-propanol were found to be necessary for selectivity enhancement. Using similar buffer additives, the same group developed and validated a method for colistin analysis. ... 

Extractions traditionally have been performed using buffers (j ) the same used to obtain the maximum response in standard curves. Unfortunately this has been a major failing of the plate diffusion assay systems. It is rare that the pH can be adjusted to the optimum necessary for greatest response simply by blending a matrix with buffer. As much as a 30 to 40% loss of activity can occur by not adjusting the pH properly analysis for residues of the streptomycins and erythromycin, for example, can yield results 20% lower by having the pH of the analyte 0.2 units below 8.0 if the pH is 0.5 units below 8.0, the loss of potency approaches 50% (14-15). 

An important area of direct biochemical interference is that caused by fluorescent or fluorescent quenching materials in the blood or urine after the administration of a drug. These interferences may be observed during catecholamine analysis in urine from patients receiving -methyldopa, tetracyclines, chlortetracyclines, oxytetracycline, erythromycin, chlorpro-mazine, or quinidine (A2, G5). 

In traditional electrophoresis, separation efficiency is limited by thermal diffusion and convection. Owing to long analysis times and low efficiencies, these procedures never enjoyed wide usage. Problems have arisen when trying to differentiate between structurally related drug residues such as streptomycin and dihydrostreptomycin, tetracyclines, lincomycin and clindamycin, and erythromycin and oleandomycin (83, 84). To overcome these problems, anticonvective media, such as polyacrylamide or agarose gels, have also been used. 

In liquid chromatographic analysis of macrolides and lincosamides, most popular is the ultraviolet detector (Table 29.4). Tylosin, tilmicosin, spiramycin, sedecamycin, and josamycin exhibit relatively strong ultraviolet absorption, but erythromycin, lincomycin, pirlimycin, and oleandomycin show extremely weak absorption in the ultraviolet region. Hence, detection at 200-210 nm has been reported for the determination of lincomycin (146). However, a combination of poor sensitivity and interference from coextractives necessitated extensive cleanup and concentration of the extract. Precolumn derivatization of pirlimycin with 9-fluorenylmethyl chloroformate has also been described to impart a chromophore for ultraviolet detection at 264 nm (140). 

Electrochemical detection is better suited to the analysis of erythromycin and lincomycin. This method of detection has been applied for the determination of erythromycin A (139) and lincomycin (154) residues in salmon tissues. Liquid chromatography coupled with mass spectrometry is particularly suitable for confirmatory analysis of the nonvolatile macrolides and lincosamides. Typical applications of this technique are through thermospray mass spectrometry, which has been used to monitor pirlimycin in bovine milk and liver (141,142), and chemical ionization, which has been applied for identification of tilmicosin (151) in bovine muscle, and for identification of spiramycin, tylosin, tilmicosin, erythromycin, and josamycin residues in the same tissue (150). 

A case-control analysis of 7405 cases and 28 327 controls suggested that concomitant use of simvastatin and erythromycin is associated with an increased risk of cataract (53). Studies in dogs have shown that some statins are associated with cataract when given in excessive doses (54). 

Although cell-free synthesis of 6-dEB was achieved, kinetic studies demonstrated that the process was very inefficient [34], The low rate of biosynthesis was likely due to the fact that the association of the three DEBS proteins in vitro was suboptimal. To simplify in vitro synthesis and to facilitate mechanistic analysis, a truncated version of the erythromycin PKS was created. The protein, DEBS 1-TE, was engineered by relocating the thioesterase (TE) from the end of DEBS 3 to the terminus of DEBS 1 (Fig. 9a,b) [35], In vivo, this bimodular construct synthesizes two triketide lactone products, one derived from propionate as a starter unit, and the other from acetate. 

Th. Cachet, K. De Turck, E. Roets, and J. Hoofmartens, Quantitative analysis of erythromycin by reversed-phase liquid chromatography using column-switching, J. Pharm. Biomed. Anal., 9 547 (1991). 

J. Paesen, D. H. Calam, J. A. Me B. Miller, G. Raiola, A. Ro-zoneski, B. Silver, and J. Hoogmartens, Collaborative study of the analysis of erythromycin by LC on wide-pore poly(stynene-dinvinylbenzene), J. Liquid Chromatogr., 76 1529 (1993). 

Q. Tang, Y. Shen, B. Wu, and W. Wang, HPLC analysis of erythromycin, Yaowu Fenxi Zazhi, 5 223 (1985). 

R. Ghali, et al., Erythromycin associated ergotamine intoxication Arteriographic and electrophysiologic analysis of a rare cause of severe ischemia of the lower extremities and associated in ischemic neuropathy. Ann. Vase. Surg. 7 291-296, 1993. 

Rae JM, Soukhova NV, Flockhart DA, Desta Z (2002) Tri-ethylenethiophosphoramide is a specific inhibitor of cytochrome P450 2B6 implications for cyclophosphamide metabolism. Drug Metab Dispos 30(5) 525-530 Riley R, Howbrook D (1997) In vitro analysis of the activity of the major human hepatic CYP enzyme (CYP3A4) using [N-methyl-14C]-erythromycin. J Pharmacol Toxicol Methods 38(4) 189-193... 

Masamune et al. have reviewed in detail the effects of double asymmetric induction not only for epoxidation, but also for the aldol, Diels-Alder, and catalytic hydrogenation reactions. The merits of this strategy are illustrated by an analysis of Woodward s synthesis" of erythromycin A (1), which has 10 chiral centers. 

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