Identification of the components of 16-membered macrolide antibiotics by LC/MS

We describe a method using liquid chromatography combined with positive electrospray ionization tandem mass spectrometry (LC/ESI-MS/MS) to identify the components of 16-membered macrolide antibiotics. Choosing three characteristic compounds (midecamycin A1, midecamycin acetate, 4″-isovalerylspiramycin III), the mass fragment pathway of this group of antibiotics was determined. The characteristics of these kinds of compounds on chromatographic behavior and UV spectrum were revealed and confirmed by the components in six examples (kitasamycin, midecamycin, meleumycin, josamycin, acetylspiramycin, 4″-acylspiramycin), whose structure were already known. Utilizing this method, some components that had never been reported in these samples were characterized by LC/MS. In comparison to the classical method, the LC/MS method is simple, rapid, sensitive, specific and suitable to application in the fields of multi-components antibiotics analysis.