Cytotoxic Peptaibols from Trichoderma strigosum .

Five new lipopeptaibols ( 1 - 5 ) and eight new 19-residue peptaibols ( 8 - 15 ) along with two known lipopeptaibols, lipovelutibols C ( 6 ) and D ( 7 ) were isolated from Trichoderma strigosum . The planar structures of the newly discovered peptaibols ( 1 - 5 , 8 - 15 ) were elucidated using 1D and 2D NMR, and UPLC-MS/MS data. The absolute configurations for new peptaibols ( 1 - 5 , 8 - 15 ) were elucidated using the advanced Marfey's method and GITC (2,3,4,6-tetra- O -acetyl-β-d-glucopyranosyl isothiocyanate) derivatization. Through analysis of CD spectra, these peptabols were found to have right-handed helical conformations. While most of the new compounds were significantly more active than the positive control, 9 , 10 , 12 , and 15 containing Ser and Leu at positions 10 and 11, respectively, were the most cytotoxic against MDA-MB-231, SNU449, SKOV3, DU145, and HCT116 cancer cell lines, and the 19-residue peptaibols were generally more potent than lipopeptaibols.