The antifungal activity of carrier peptides, L-arginyl-X-L-phenylalanine, containing amino acid antagonists or atypical non-biogenic D-amino acids in the central position.

Eleven analogues of L-arginyl-D-allo-threonyl-L-phenylalanine, a naturally occurring peptide with antifungal activity, were synthesized. Two tripeptides of the form L-arginyl-X-L-phenylalanine (X = p-F-DL-phenylalanine or m-F-DL-tyrosine) inhibited Aspergillus fumigatus and Aspergillus flavus. In comparison with the free antagonists, the tripeptide-bound antagonists were more active against Candida-albicans-isolates which means that the amino acid sequence may serve as carrier function: it enhances delivery or uptake of the antimetabolite.