Cyclic heptapeptides with metal binding properties isolated from the fungus Cadophora malorum from Antarctic soil

Abstract

The Antarctic fungus Cadophora malorum produces previously undescribed cyclic heptapeptides (cadophorin A and B) containing an anthranilic acid residue. The planar structure of these peptides was determined by high-resolution mass spectrometry combined with extensive 1D and 2D NMR spectroscopy. The absolute configuration of the amino acids was determined by Marfey’s method, with HPLC analysis of FDVA (Nα-(2,4-dinitro-5-fluorphenyl)-l-valinamide) derivatives making use of a PFP column. Remarkably, cadophorin 2 possesses both the uncommon d-Ile and d-allo-Ile in its structure. The peptides have metal binding properties as shown by LCMS with post column addition of metal salt solutions. These results were supported by DFT calculations. Graphical Abstract: [Figure not available: see fulltext.]