Antifungal cyclic peptides from Psammosilene tunicoides

Three new cyclic peptides, tunicyclins B-D, and a known cyclic peptide, psammosilenin B, were isolated from the root of Psammosilene tunicoides. The structures of new cyclic peptides were elucidated by extensive NMR and MS analysis. Tunicyclin B contains an unusual α,β-dehydrotryptophan (Δ(Z)-Trp) residue, previously reported from marine sponges and bacteria. Tunicyclin D showed a broad spectrum of antifungal activity against Candida albicans (SC5314), Candida albicans (Y0109), Candida tropicalis, Candida parapsilosis, and Cryptococcus neoformans (BLS108) with MIC(80) values of 4.0, 16.0, 0.25, 1.0, and 1.0 μg mL(-1), respectively.