Tylosin B

The decomposition of the 16-membered ring macrolide antibiotic tylosin A in aqueous buffers has been investigated in the pH range 2-13, by means of a liquid chromatographic assay with ultraviolet detection at 280 nm. In acidic medium, tylosin A is converted into tylosin B, while in neutral and alkaline medium, tylosin A aldol is formed together with a number of polar decomposition products of unknown identity. The decomposition kinetics have been studied as a function of the type and concentration of the buffer, ionic strength, pH and temperature.

The 16-membered macrolide antibiotics (e.g. tylosin A and josamycin) are mainly used in veterinary medicine, and are much less studied than their 14- and 15-membered erythromycin-based cousins. Although these antibiotics have similar antibacterial profiles, with activity primarily against Gram-positive and a limited range of Gram-negative organisms, the 16-membered macrolides show some advantages. These include better gastrointestinal tolerance, lack of drug-drug interactions, and activity against certain resistant bacterial strains by extension of the peptide tunnel reach allowing additional interactions. In addition to antibacterial activity, the most famous representative of the class, tylosin A, as well as some derivatives of desmycosin (tylosin B), have shown antimalarial activity. Such activity has also been observed in the 14-membered macrolide antibiotics, azithromycin, solithromycin and clindamycin. This antimalarial activity provides the opportunity to investigate these drugs as cheap and effective antimalarials. This is an overview of the latest research on biosynthesis, structure, chemical properties and mode of action of 16-membered macrolides, with special emphasis on their most explored members: tylosin A and josamycin.

Tylosin is a widely used macrolide antibiotic for therapeutics and growth promotion in swine, beef cattle, and poultry production. Through various routes such as manure application, emission, inappropriate disposal, etc., tylosin enters the environment. The fate of tylosin in the environment is not yet fully understood. In this study, two photoreaction products of tylosin in water were identified as isotylosin A alcohol (E,Z) and isotylosin A aldol (E,Z). Tylosin A, B, C, D, isotylosin A alcohol, and isotylosin A aldol were purified, and immunological cross-reactivities of these tylosin-related compounds were tested with a specificity of 26% for tylosin B, 19% for tylosin C, 106% for tylosin D, 121% for isotylosin A alcohol, and 46% for isotylosin A aldol, compared to 100% for tylosin A. Competitive direct enzyme-linked immunosorbent assay (ELISA) for tylosin detection in water was compared with a high-performance liquid chromatography (HPLC) method by analyzing the same water samples from a study of tylosin dissipation in water. ELISA kits detect the other tylosin-related compounds besides tylosin A, which can result in differences in tylosin determination in water.