<jats:p> Two new fluvirucin aglycones, named fluvirucinins C<jats:sub>1</jats:sub> and C<jats:sub>2</jats:sub> (1-2), have been isolated from the ethyl acetate mycelial cake extract of the fermentation broth of a marine sponge-associated actinomycete. Fluvirucinins C<jats:sub>1</jats:sub> (1) and C<jats:sub>2</jats:sub> (2) represent a new type of 14-membered macrolactam aglycon, structurally related with the common aglycon of the known fluvirucins. Their structures were elucidated on the basis of 1D and 2D NMR analyses, as well as HRESIMS experiments. The antimicrobial and cytotoxic activities of compounds 1 and 2 have been evaluated, but no significant activities found for fluvirucinins C<jats:sub>1</jats:sub> and C<jats:sub>2</jats:sub>.