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

Talaromides A–C, Bioactive Cyclic Heptapeptides from Talaromyces siglerae Isolated from a Marine Sponge

“…It is noteworthy that talaromide B (2) shares the same amino acid sequence as talaromin A 10 and cadophorin A, 11 while talaromide A (1) has an identical amino acid sequence to talaromin B 10 and cadophorin B. 11 The key differences between these compounds are the absolute configurations of the amino acid residues Tyr and Ile. Unlike talaromins and cadophorins, talaromides are characterized by a predominance of D amino acids.…”

“…Cadophorins A and B, known for their weak metal-binding properties and antifungal activity, were recently obtained from cultures of the Antarctic soil-derived fungus Cadophora malorum . However, only the NMR data of the trans -Pro conformers of these known compounds have been reported, despite the observation of duplicated signals. , All six compounds represent quite unusual examples of cyclic peptides bearing a β-amino acid anthranilic acid (AA) adjacent to proline. This Pro-AA dipeptide motif may constrain the flexibility of the molecule and enhance specificity for target sites.…”

“…Talaromins A and B, which exhibit no significant cytotoxicity or antibacterial activity, were isolated from cultures of the endophytic fungus Talaromyces wortmannii . Cadophorins A and B, known for their weak metal-binding properties and antifungal activity, were recently obtained from cultures of the Antarctic soil-derived fungus Cadophora malorum . However, only the NMR data of the trans -Pro conformers of these known compounds have been reported, despite the observation of duplicated signals. , All six compounds represent quite unusual examples of cyclic peptides bearing a β-amino acid anthranilic acid (AA) adjacent to proline.…”