Acremopeptaibols A–F, 16-Residue Peptaibols from the Sponge-Derived Acremonium sp. IMB18-086 Cultivated with Heat-Killed Pseudomonas aeruginosa

Six new 16-residue peptaibols, acremopeptaibols A-F (1-6), along with five known compounds, were isolated from the cultures of the sponge-associated fungus Acremonium sp. IMB18-086 grown in the presence of the autoclaved bacterium Pseudomonas aeruginosa on solid rice medium. The peptaibol sequences were established based on comprehensive analysis of 1D and 2D NMR spectroscopic data in conjunction with HRESIMS/MS experiments. The configurations of the amino acid residues were determined by advanced Marfey's analysis. Compounds 1-6 feature the lack of the highly conserved Thr6 and Hyp10 residues in comparison with other members of the SF3 subfamily peptaibols. A plausible biosynthetic pathway of compounds 1-6 was proposed on the basis of genomic analysis. Compounds 1, 5, 7, and 10 exhibited significant antimicrobial activity against Staphylococcus aureus, methicillin-resistant S. aureus, Bacillus subtilis, and Candida albicans. Compounds 7-10 showed potent cytotoxicities against the A549 and/or HepG2 cancer cell lines.