Bioactive Peptaibols of Forest-Derived Trichoderma Isolates from Section Longibrachiatum

Filamentous fungi are producers of a large number of secondary metabolites with wide spectra of biological effects. Among them, peptaibols represent a group of compounds produced mainly by members of the mycotrophic filamentous fungal genus Trichoderma. A simple peptaibol characterization strategy including purification and structural elucidation steps was applied to examine the peptaibol production of three strains from the Longibrachiatum section of genus Trichoderma, T. aethiopicum TUCIM 1817, T. novae-zelandiae TUCIM 4158 and T. pseudokoningii TUCIM 1277, all deriving from natural forest habitats (disturbed semiforest, native Notophagus forest and the bark of Beilschmiedia tawa, respectively). After the solid phase clean-up of culture extracts, mass spectrometric analysis of peptaibols produced by the examined strains was performed by on-line reversed-phase high performance liquid chromatography coupled to electrospray ionization ion trap mass spectrometry. All three examined species produced 20-residue trichobrachin-like compounds, some of which are known from the literature, while others proved to be different from any peptaibols reported so far. The spectra of the peptaibols produced by these isolates were entirely different from each other. The largest amount of peptaibols consisting of four yet unknown compounds was produced by T. pseudokoningii TUCIM 1277, while ten and eight new, trichobrachin-like compounds were detected from T. aethiopicum TUCIM 1817 and T. novae-zelandiae TUCIM 4158, respectively. Feline fetal lung cell proliferation inhibition tests and membrane damage bio-assay with boar sperm cells revealed that although T. novae-zelandiae TUCIM 4158 produced the least amount of peptaibols, its compounds were the most inhibitory to mammalian cells.