Isolation of fungi using the diffusion chamber device FIND technology.

Fungi are an important source of bioactive metabolites. The Fungal one-step IsolatioN Device (FIND) technology allows the isolation of rare fungi from terrestrial and marine samples. The FIND comprises a multi-chambered micro agar plate, where initially only one fungal part (e.g., hyphal cell, mycelial fragment or spore) is located in each chamber. After inoculation the device is placed back into the original natural environment of sample collection, to ensure favourable growth conditions. Experiments were carried out with terrestrial soil and marine sediment, as well as sea water samples to validate this method. This yielded axenic cultures of 12 different filamentous fungi, one of them being the marine-adapted fungal strain Heydenia cf. alpina. The latter produced two new terpenoids, which are the first secondary metabolites from this genus.

Phenalenones: insight into the biosynthesis of polyketides from the marine alga-derived fungus Coniothyrium cereale.

The marine alga-derived fungus Coniothyrium cereale is a prolific producer of phenalenones. These polyketides were shown to possess antimicrobial effects and inhibitory activity towards the protease human leucocyte elastase (HLE). The current study focused on the biosynthesis of eight different structural types of phenalenones, comprising the natural products rousselianone A' (1), coniosclerodin (3), cereolactam (12), cereoaldomine (15), and trypethelone (16). Solid agar cultures of C. cereale were used to follow up the incorporation of [1-(13)C] labeled acetate into these metabolites. Taking the respective mechanisms of polyketide metabolism into account, the labeling pattern was interpreted, thus providing a hypothesis for the biosynthetic formation of the phenalenones. The polyketide skeleton of the phenanthrene-based compound cereolactam is proposed to be formed through degradation of a heptaketide by loss of two carbon atoms.

Isolation, structure elucidation and total synthesis of lajollamide A from the marine fungus Asteromyces cruciatus.

The marine-derived filamentous fungus Asteromyces cruciatus 763, obtained off the coast of La Jolla, San Diego, USA, yielded the new pentapeptide lajollamide A (1), along with the known compounds regiolone (2), hyalodendrin (3), gliovictin (4), ¹N-norgliovicitin (5), and bis-N-norgliovictin (6). The planar structure of lajollamide A (1) was determined by Nuclear Magnetic Resonance (NMR) spectroscopy in combination with mass spectrometry. The absolute configuration of lajollamide A (1) was unambiguously solved by total synthesis which provided three additional diastereomers of 1 and also revealed that an unexpected acid-mediated partial racemization (2:1) of the L-leucine and L-N-Me-leucine residues occurred during the chemical degradation process. The biological activities of the isolated metabolites, in particular their antimicrobial properties, were investigated in a series of assay systems.