Longibramides A–E, Peptaibols Isolated from a Mushroom Derived Fungus Trichoderma longibrachiatum Rifai DMG‐3‐1‐1

Abstract

Five new peptaibols, longibramides A–E (1–5) with 11 amino acid residues, were isolated from a fungus Trichoderma longibrachiatum Rifai DMG‐3‐1‐1, which was isolated from a mushroom Clitocybe nebularis (Batsch) P. Kumm collected from coniferous forest in the subboreal area of northeast China. The structures of longibramides A–E were determined by their spectroscopic data (NMR and MS‐MS spectra), their absolute configurations were determined by X‐ray diffractions and Marfey s analyses. The X‐ray diffractions of longibramides A, B, and the similar CD spectra of A–E showed that they all had α‐helix conformations. Longibramides B and E showed moderate cytotoxicities against BV2 and MCF‐7 cells and also showed some inhibitory effects against methicillin‐resistant Staphylococcus aureus MRSA T144. L‐trans‐Hyp was not commonly found in natural peptaibols, which was the 6th or 10th amino acid residue in longibramides C–E. The X‐ray diffractions of longibramides A and B afforded the accuracy conformations of their secondary structures, which maybe help to interpret the structure‐activity relationships of the family of peptaibols in the future.