Microbial transformation of 20(S)-protopanaxatriol by Mucor spinosus

Microbial biotransformation of 20(S)-protopanaxatriol (1) by the fungus Mucor spinosus (AS 3.3450) yielded four new metabolites, the structures of which were determined to be 12-oxo-15alpha-hydroxyl-20(S)-protopanaxatriol (2), 27-hydroxyl-20(S)-protopanaxatriol (3), 12-oxo-26-hydroxyl-20(S)-protopanaxatriol (4), and 12-oxo-27-hydroxyl-20(S)-protopanaxatriol (5), respectively, on the basis of their chemical and spectroscopic data. All the new metabolites, as well as the substrate, had significant cytotoxic effects on HL-60 cells (human leukemia cells).