Eleven‐Residue Peptaibols Isolated from Trichoderma longibrachiatum Rifai DMG‐3‐1‐1and Their Structure‐Activity Relationship

Total 23 eleven‐residue peptaibols, including five reported ones (1–5) in our previous work, were isolated from the fungus Trichoderma longibrachiatum Rifai DMG‐3‐1‐1, which was obtained from the mushroom Clitocybe nebularis (Batsch) P. Kumm. The structures of the 13 new peptaibols (6–10 and 12–19) were determined by their NMR and MALDI‐MS/MS data, their absolute structures were further determined by Marfey's analyses and their ECD data. Careful comparison of the structures of 1–23 showed that only seven residues varied including the 2nd (Gln2/Asn2), 3rd (Ile3/Val3), 4th (Ile4/Val4), 6th (Pro6/Hyp6), 8th (Leu8/Val8), 10th (Pro10/Hyp10) and 11th (Leuol11/Ileol11/Valol11) residues. Comparison of the IC50s against the three tested cell lines of 1–23 indicated that 2nd, 3rd and 4th amino acid residues affected their cytotoxicities powerfully. Compounds 2, 5, 9, 11, 21 and 22 showed moderate antibacterial activities against Staphylococcus aureus MRSA T144, which also showed stronger cytotoxicities against BV2 and MCF‐7 cells.