A third metabolite from Spicaria divaricata NRRL 5771

Antibacterial activities of viriditoxin congeners and synthetic analogues against fish pathogens

Viriditoxin is a fungal secondary metabolite of the fungus Paecilomyces variotii derived from the inner tissues of the giant jellyfish Nemopilema nomurai. Viriditoxin exhibits antibacterial activity against Streptococcus iniae and Streptococcus parauberis, which are major pathogens of aqua cultured fish. Viriditoxin induced abnormal cell morphologies in the fish pathogens S. iniae and S. parauberis, presumably by inhibiting FtsZ polymerization as was previously observed in Escherichia coli. Synthetic analogues of viriditoxin, designed based on docking simulation results to FtsZ of Staphylococcus aureus, were prepared and compared with viriditoxin for antibacterial activity. Reconstitution of free hydroxyl or carboxyl groups of the methoxyl or methyl ester groups of viriditoxin led to significant reduction of antibacterial activity, implying that the natural molecule is optimized for antibacterial activity to deter bacteria potentially harmful to Paecilomyces.

Cladosporinone, a new viriditoxin derivative from the hypersaline lake derived fungus Cladosporium cladosporioides

A new cytotoxic viriditoxin derivative, cladosporinone (1), along with the known viriditoxin (2) and two viriditoxin derivatives (3 and 4) were obtained from the fungus Cladosporium cladosporioides isolated from the sediment of a hypersaline lake in Egypt. The structure of the new compound (1) was determined by 1D and 2D NMR measurements as well as by high-resolution ESIMS and electronic circular dichroism spectroscopy. All isolated compounds were studied for their cytotoxicity against the murine lymphoma cell line L5187Y and for their antibiotic activity against several pathogenic bacteria. Viriditoxin (2) was the most active compound in both bioassays. Compound 1 also exhibited strong cytotoxicity against the murine lymphoma cell line L5187Y with an IC50 value of 0.88 μm, whereas its antibiotic activity was weak.

Naphthopyranones--isolation, bioactivity, biosynthesis and synthesis

The 1H-naphtho[2,3-c]pyran-1-one (naphthopyranone) moiety forms the structural framework of a group of secondary metabolites that have been isolated from a range of organisms including fungi, bacteria, lichen and plants. This review documents the known naturally occurring naphthopyranones - their isolation, biosynthesis and biological activity. A survey of methods reported for the synthesis of naphthopyranone natural products is presented.