Immunosuppressive activity in the series of cycloamanide peptides from mushrooms

The immunosuppressor activity of the cycloamanides A, B, C, and D, and two of their D-amino acid residue-containing analogues, was examined using PFC (plaque forming cell) and DTH (delayed type hypersensitivity) tests. It was found that cycloamanide A (CyA A, II) [c-(Phe-Phe-Ala-Gly-Pro-Val-)] and its D-Phe-containing analogue III [c-(Phe-D-Phe-Ala-Gly-Pro-Val-)] are the most potent immunosuppressors of the whole series. The retroanalogue of III [c-(D-Phe-Val-Pro-Gly-Ala-)] was found to be less active than III. The immunosuppressor activity of O-carboxymethyl-Tyr6-antamanide (I) was also tested. It was found that the substitution of one of the Phe residues of ANT by O-carboxymethyl-Tyr does not substantially affect the immunosuppressor activity.