Potential Antiviral Xanthones from a Coastal Saline Soil Fungus Aspergillus iizukae

Five new (1–5) and two known xanthones (6 and 7), one of the latter (6) obtained for the first time as a natural product, together with three known anthraquinones, questin, penipurdin A, and questinol, were isolated from the coastal saline soil-derived Aspergillus iizukae by application of an OSMAC (one strain many compounds) approach. Their structures were determined by interpretation of nuclear magnetic resonance (NMR) and high-resolution electrospray ionization mass spectroscopy (HRESIMS) data, as well as comparison of these data with those of related known compounds. Antiviral activity of xanthones 1−7 was evaluated through the cytopathic effect (CPE) inhibition assay, and compound 2 exhibited distinctly strong activity towards influenza virus (H1N1), herpes simplex virus types 1 (HSV-1) and 2 (HSV-2) with IC(50) values of 44.6, 21.4, and 76.7 μM, respectively, which indicated that it was worth to further investigate it as a potential lead compound. The preliminary structure-activity relationship of the xanthones is discussed.