Polymyxin analysis

United States Pharmacopoeia 28 [1] describes a microbiological method under antibiotics-microbial assays for the analysis of OTC and nystatin capsules, OTC and nystatin for oral suspension, OTC HC1 and hydrocortisone ointment, and OTC HC1 and polymyxin B sulfate ointment. The methods are relative rather than absolute, which are based on the determination of the level of oxytetracycline by a microbiological response to a series of standard oxytetracycline concentrations by a... 

Kang, J. W., Van Schepdael, A., Orwa, J. A., Roets, E., and Hoogmartens, J. (2000). Analysis of polymyxin B sulfate by capillary zone electrophoresis with cyclodextrin as additive. Method development and validation. J. Chromatogr. A 879(2), 211—218. 

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. ... 

The antibioticogram analysis showed that in the long term AVL conditions, the microflora were resistant to the majority of antibiotics used and the application of these drugs were ineffective in about 50% cases, which led to the development of different broncho-pulmonary complications. The identified microorganisms showed mild resistance to amikacin, meropenem and polymyxin and total resistance to cephalosporins with exception of Staphylococcus spp. (Table 26.3). 

Imaizumi H, Maruyama I (2001) Simultaneous measurement of anandamide and 2-arachidonoylglycerol by polymyxin B-selective adsorption and subsequent high-performance liquid chromatography analysis increase in endogenous cannabinoids in the sera of patients with endotoxic shock. Anal Biochem 294 73-82... 

The molecular weight of polymyxin B was shown by the method of partial substitution to be 1,150 d 10 per cent. Quantitative amino acid analysis yielded the amino acids a,y-diaminobutyric acid, L-threonine, D-phenylalanine and L-leucine in the molar proportions 6 2 1 1. Because no free a-carboxyl- and no free a-amino groups could be detected, polymyxin Bi had to be of a cyclic nature . Neither pepsin nor trypsin was found to attack the molecule and therefore partial hydrolysis and separation of the fragments was used for the elucidation of the structure. Of the 14 fragments isolated and identified, seven key peptides were necessary for proposing four tentative structures for polymyxin Two were formulated with a ring... 

Pharmacologic and Toxicologic Studies with the Polymyxins. I. Gas Chromatographic Procedure for the Analysis of Colistin in Urine by Its Content of D-Leucine... 

These findings suggest that polymyxin formation and sporulation are subject to joint control and that there may be a functional relationship between these processes. However, even though polymyxin is undoubtedly an important metabolite, as the amount produced may exceed 10% of the bacterial dry weight, very few clues exist as to its possible function. It had been suggested that peptide antibiotics are structural components of the spore coat (Bernlohr and Novelli, 1962), and Jann and Eichhorn (1964) have reported the presence of DBA in spores of B. circulans. However, careful analysis of spores and sporecoats of B. polymyxa strain Pfizer 2459 failed to reveal the presence of significant amounts... 

SiLAEV, A. V., V. M. Stepanov, E. P. Yulikova, E. V. Troshko, and E. D. Levin Chemistry of polymyxin M. I. Qualitative amino acid composition and analysis of end groups. Zhur. Obshchei Khim. 31, 297 (I96la). 

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