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

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.