The fungus Pestalotiopsis guepini as a model for biotransformation of ciprofloxacin and norfloxacin

The metabolism of the fluoroquinolone drugs ciprofloxacin and norfloxacin b y Pestalotiopsis guepini strain P-8 was investigated. Cultures were grown a t 28 degreesC in sucrose/peptone broth for 18 days after dosing with ciprof loxacin (300 muM) or norfloxacin (313 muM). Four major metabolites were pro duced from each drug; and these were purified by high-performance liquid ch romatography and identified by mass spectrometry and proton nuclear magneti c resonance spectroscopy. Ciprofloxacin metabolites included N-acetylciprof loxacin (52.0%), desethylene-N-acetylciprofloxacin (9.2%), N-formylciproflo xacin (4.2%), and 7-amino-1-cyclopropyl-6-fluoro-4-oxo-1,4-dihydroquinoline -3-carboxylic acid (2.3%). Norfloxacin metabolites included N-acetylnorflox acin (55.4%), desethylene-N-acetylnorfloxacin (8.8%), N-formylnorfloxacin ( 3.6%), and 7-amino-1-ethyl-6-fluoro-4-oxo-1,4-dihydroquinoline-3-carboxylic acid (2.1%). N-Formylciprofloxacin and the four transformation products fr om norfloxacin are all known to be mammalian metabolites.