The Purification of Highly Polar Impurities in Antibiotics by C18AQ Columns

Mingzu Yang, Bo Xu
Application R&D Center

Introduction
Antibiotics are a class of secondary metabolites produced by microorganisms (including bacteria, fungi, actinomycetes) or similar compounds which are chemically synthesized or semi-synthesized. Antibiotics could inhibit the growth and survival of other microorganisms. The first antibiotic discovered by human, penicillin, was discovered by British microbiologist Alexander Fleming in 1928. He observed that the bacteria in the vicinity of the mold could not grow in the staphylococcus culture dish which was contaminated with mold. He postulated that the mold must secrete an antibacterial substance, which he named penicillin in 1928. However, the active ingredients were not purified at that time. In 1939, Ernst Chain and Howard Florey of Oxford University decided to develop a drug that could treat bacterial infections. After contacting Fleming to obtain strains, they successfully extracted and purified penicillin from the strains. For their successful development of penicillin as a therapeutic drug, Fleming, Chain and Florey shared the 1945 Nobel Prize in Medicine.

Antibiotics are used as antibacterial agents to treat or prevent bacterial infections. There are several main categories of antibiotics used as antibacterial agents: β-lactam antibiotics (including penicillin, cephalosporin, etc.), aminoglycoside antibiotics, macrolide antibiotics, tetracycline antibiotics, chloramphenicol (total synthetic antibiotic), and etc. The sources of antibiotics include biological fermentation, semi-synthesis and total synthesis. The antibiotics produced by biological fermentation need to be structurally modified by chemical methods due to chemical stability, toxic side effects, antibacterial spectrum and other issues. After chemically modified, the antibiotics could achieve increased stability, reduced toxic side effects, expanded antibacterial spectrum, reduced drug resistance, improved bioavailability, and thereby improved effect of drug treatment. Therefore, semi-synthetic antibiotics are currently the most popular direction in the development of antibiotic drugs.

In the development of semi-synthetic antibiotics, antibiotics have the properties of low purity, lots of by-products and complex components since they are derived from microbial fermentation products. In this case, the analysis and control of impurities in semi-synthetic antibiotics is particularly important. In order to effectively identify and characterize impurities, it is necessary to obtain a sufficient amount of impurities from the synthetic product of semi-synthetic antibiotics. Among the commonly used impurity preparation techniques, flash chromatography is a cost-effective method with advantages such as large sample loading amount, low cost, time saving, etc. Flash chromatography has been more and more employed by synthetic researchers.

In this post, the main impurity of a semi-synthetic aminoglycoside antibiotic was utilized as the sample and purified by a SepaFlash C18AQ cartridge combined with the flash chromatography system SepaBean™  machine. The target product meeting the requirements was successfully obtained, suggesting a highly efficient solution for the purification of these compounds.