Twonew xanthocillin type antibiotics, darlucin A (1) and B (2), were isolated from fermentations of Sphaerellopsis filum {Darluca filum). Their structures were established by spectroscopic methods. The darlucins are the first knowncompoundswith a 1 ,2-diisocyanoalkene moiety. Both compounds exhibited antibacterial, antifungal and weak cytotoxic activities.During our screening of mycophilic fungi growing on or in fruiting bodies of asco-and basidiomycetes, cultures of the widespread coelomycete Sphaerellopsisfilum (Biv.-Bern. ex Fr.) Sutt. (Darluca filum) were found to produce antimicrobial metabolites. S. filum, the anamorph ofEudarluca caricis (Fr.) O. Eriks., is a destructive mycoparasite occurring world wide on rust fungi1'2*. It is known from more than 360 hosts3). For some time, S.filum was considered to be useful for biological control of rust fungi, but no commercial product has been developed4'5*. Toxins involved in the destruction of the host or other secondary metabolites from S. filum are not known. Therefore the antimicrobial active metabolites were isolated and elucidation of the structures revealed two new xanthocillin type metabolites. In this paper the production, isolation, biological activities and elucidation of the structures of darlucin A (1) and B (2) will be reported.
Producing OrganismSphaerellopsis filum, CBS658.79, was cultivated and maintained on YMGagar composed of (g/liter): yeast extract 4, malt extract 10, glucose 4, and agar 15, pH 5.5. Freeze-dried cultures were made in skim milk from pycnidial cultures for long-term storage. After several subcultures, the strain lost the ability to sporulate. In this case, the strain was recultivated from lyophilized material.Fermentation Fermentations were carried out in a 20-liter fermentor (Biolafitte C-6) at 22°C with an aeration rate of 3.0 liters/minute and agitation (130 rpm). The fermentation mediumwas composed of (g/liter): maltose 20, glucose 10, peptone 2, yeast extract 1, KH2PO4 0.5, MgSO4-7H2O 1, ZnSO4-7H2O 0.002, FeCl3 0.01 and CaCl2-2H2O 0.074. The pH was adjusted to 5.5 prior to sterilization. As inoculum, a well grown culture in the same medium (250ml) was used. Antifungal activity during fermentation was measured in the agar plate diffusion assay with Nematospora coryli as test organism.Parts of the results have been presented at the 33rd ICAAC, NewOrleans, Louisiana, October 1993.