A novel compound nafuredin, was isolated as an inhibitor of anaerobic elect
ron transport (NADH-fumarate reductase). It was obtained from culture broth
of Aspergillus niger FT-0554 isolated from a marine sponge, The structure
was elucidated as an epoxy-delta -lactone with an attached methylated olefi
nic side chain on the basis of spectral analysis.