[Studies on acetylspiramycin. 1. Separation and chemical structures of acetylspiramycin components]

1. A macrolide antibiotic acetylspiramycin (ASPM) was separated into seven fractions using high performance liquid chromatography (HPLC) with Lichrosorb RP-8 and mobile phase of a mixed solvent of 0.025M phosphate ammonium (pH 7.4) and acetonitrile at a ratio of 10:18. 2. Five components were purified over 90%, and analyzed using mass spectroscopy, 1H NMR, and 13C NMR, and their chemical structures were determined as 4''-acetylspiramycin I, 4''-acetylspiramycin II, 4''-acetylspiramycin III, 3'',4''-diacetylspiramycin II and 3'',4''-diacetylspiramycin III, respectively. 3. The weight component ratio of the seven fractions of ASPM separated by HPLC was constant throughout several lots of ASPM which had been stocked for nearly 15 years at room temperature, indicating an excellent chemical stability of the antibiotic. 4. Some physicochemical parameters were determined for the five ASPM components. Solubilities in water at 24 degrees C were in a range from 0.14 mg/ml to 4.9 mg/ml, and they were, in the decreasing order, 3'',4''-diacetylspiramycin III, 3'',4''-diacetylspiramycin I 4''-acetylspiramycin III, 4''-acetylspiramycin II, and 4''-acetylspiramycin I. Relationships between solubilities and numbers and positions of acyl substituents in spiramycin molecule are discussed.