Psychrophilins E-H and versicotide C, cyclic peptides from the marine-derived fungus Aspergillus versicolor ZLN-60.

Four new cyclic peptides, psychrophilins E-H (1-4), possessing a rare amide linkage between the carboxylic acid in anthranilic acid (ATA) and the nitrogen from an indole moiety, along with a new ATA-containing hexapeptide, versicotide C (5), were obtained from the culture of the marine-derived fungus Aspergillus versicolor ZLN-60. The structures, including absolute configurations, were elucidated by a combination of HRESIMS, NMR, X-ray crystallography, TDDFT ECD calculations, and Marfey's method. Versicotide C (5) is the first natural cyclic hexapeptide containing two anthranilic acids. Compounds 1-5 were not cytotoxic, and compound 3 showed potent lipid-lowering effects.