Extremophilic fungi have received considerable attention recently as new promising sources of biologically active compounds with potential pharmaceutical applications. This study investigated the secondary metabolites of a marine-derived Penicillium ochrochloron isolated from underwater sea sand collected from the North Sea in St. Peter-Ording, Germany. Standard techniques were used for fungal isolation, taxonomic identification, fermentation, extraction, and isolation of fungal secondary metabolites. Chromatographic separation and spectroscopic analyses of the fungal secondary metabolites yielded eight compounds: talumarin A (1), aspergillumarin A (2), andrastin A (3), clavatol (4), 3-acetylphenol (5), methyl 2,5-dihydro-4-hydroxy-5-oxo-3-phenyl-2-furanpropanoate (6), emodin (7) and 2-chloroemodin (8). After co-cultivation with Bacillus subtilis, the fungus was induced to express (-)-striatisporolide A (9). Compound 1 was evaluated for antibacterial activity against Staphylococcus aureus, Acinetobacter baumannii, Mycobacterium smegmatis, and M. tuberculosis, as well as cytotoxicity against THP-1 cells. The compound, however, was not cytotoxic to THP-1 cells and had no antibacterial activity against the microorganisms tested. The compounds isolated from P. ochrochloron in this study are well-known compounds with a wide range of beneficial biological properties that can be explored for pharmaceutical, agricultural, or industrial applications. This study highlights the bioprospecting potential of marine fungi and confirms co-cultivation as a useful strategy for the discovery of new natural products.
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