Abstract
The OSMAC (one strain many compounds) concept is a cultivation-based approach to increase the diversity of secondary metabolites in microorganisms. In this study, we applied the OSMAC-approach to the endophytic fungus Trichocladium sp. by supplementation of the cultivation medium with 2.5% phenylalanine. This experiment yielded five new compounds, trichocladiol (1), trichocladic acid (2), colletodiolic acid (3), colletolactone (4) and colletolic acid (5), together with five previously described ones (6–10). The structures were elucidated via comprehensive spectroscopic measurements, and the absolute configurations of compound 1 was elucidated by using TDDFT-ECD calculations. For formation of compounds 3–5, a pathway based on colletodiol biosynthesis is proposed. Compound 6 exhibited strong antibacterial activity against methicillin-resistant Staphylococcus aureus with a minimal inhibitory concentration (MIC) of 0.78 μM as well as a strong cytotoxic effect against the human monocytic cell line THP1 with an IC50 of 0.7 μM. Compound 8 showed moderate antibacterial activity against Mycobacterium tuberculosis with a MIC of 25 μM and a weak cytotoxic effect against THP1 cells with an IC50 of 42 μM.
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