Biotransformation of terpenes from Stemodia maritima by Aspergillus niger ATCC 9142

Incubation of stemodin (1) in cultures of Aspergillus niger ATCC 9142 resulted in the production of 2alpha,3beta,13-trihydroxystemodane (2), 2alpha,7beta,13-trihydroxystemodane (3) and 2alpha,13,16beta-trihydroxystemodane (4), while stemodinone (5) afforded 13,18-dihydroxystemodan-2-one (6) and 13,16beta-dihydroxystemodan-2-one (7). Four novel metabolites were obtained from the bioconversion of stemarin (8) by the fungus, namely 18-hydroxystemaran-19-oic acid (9), 7beta,18-dihydroxystemaran-19-oic acid (10), 7alpha,18,19-trihydroxystemarane (11) and 1beta-hydroxystemaran-19-oic acid (12). 19-N,N-Dimethylcarbamoxy-13-hydroxystemarane (13) was also transformed to afford 19-N,N-dimethylcarbamoxy-13,17xi,18-trihydroxystemarane (14).