Microbial transformations of S-naproxen by Aspergillus niger ATCC 9142

Aspergillus niger ATCC 9142 was used to catalyze the biotransformation of S(-)-naproxen (1) to three major metabolites that were isolated by solvent extraction, purified chromatographically, and characterized by mass spectrometry and NMR spectroscopy. Metabolites were identified as O-desmethylnaproxen (2), 7-hydroxynaproxen (3) and 7-hydroxy-O-desmethyinaproxen (4). The kinetics of naproxen biotransformation to 2 and 4 was established over an 84 h period to show that naproxen was completely metabolized at 36 h, the major metabolite was O-desmethylnaproxen at 24 h, and the 7-hydroxy-O-desmethylnaproxen that was formed after 24 h.