Quantitative Determination of Major Active Components in Polymyxin B Medicinal Products by NMR Spectroscopy

INTRODUCTION . Polymyxin B is a natural multicomponent antibiotic used in its sulfate form for the treatment of infections caused by multidrug-resistant Gram-negative bacteria. Pharmacopoeial standards for polymyxin B medicinal products include limits for the sum of polymyxins B1, B2, B3, and B1-I and for individual polymyxins B3 and B1-I. Since polymyxins B1 and B2 differ in their nephrotoxicity, it is important to establish individual limits for their content in polymyxin B medicinal products. Establishing individual limits for polymyxins B1 and B2 requires determining the component composition of various polymyxin B samples. However, high-performance liquid chromatography (HPLC) may not always provide accurate results because of the lack of reference standards for individual polymyxin B components. AIM. This study aimed to investigate the possibility of quantifying polymyxins B1, B2, B3, and B1-I in polymyxin B medicinal products by nuclear magnetic resonance (NMR) spectroscopy. MATERIALS AND METHODS . The study focused on a reference standard for polymyxin B sulfate, as well as polymyxin B medicinal products from different manufacturers. NMR measurements were performed on an Agilent DD2 600 MHz NMR spectrometer. The study used high-performance liquid chromatography (HPLC) on an Agilent 1200 HPLC system as the reference method. RESULTS . The 13C NMR spectrum contained signals characteristic of polymyxins B1, B2, B3, and B1-I. The authors determined the mole fractions of polymyxins B1, B2, B3, and B1-I by the internal normalisation method using the integrated intensities of the characteristic NMR signals. The results of NMR and HPLC quantification of the specified components in polymyxin B samples practically coincided (with due regard to the confidence intervals). CONCLUSIONS. According to the results, the 13C NMR analytical procedure can identify and quantify the major active components in polymyxin B sulfate medicinal products without reference standards for individual polymyxins.