Microbial transformation of the germacranolide pyrethrosin (1) using Rhizop
us nigricans NRRL 1477 has resulted in the isolation of 6 alpha -acetoxy-1
beta ,4 alpha -dihydroxy-5,7 alphaH,8 betaH-eudesm-11 beta ,13-dihydro-8,12
-olide (5), a new eudesmanolide-type metabolite, in addition to the previou
sly reported eudesmanolides: 2, 3, 4, and 6. The structure elucidation of t
hese metabolites was based primarily on 1D and 2D NMR analyses. The isolate
d metabolites exhibited cytotoxic, antifungal, and antiprotozoal activities
.