A New Radical Scavenging Anthracene Glycoside, Asperflavin Ribofuranoside, and Polyketides from a Marine Isolate of the Fungus Microsporum

A new anthracene glycoside, asperflavin ribofuranoside (1), and the previously described polyketides, flavoglaucin (2), isodihydroauroglaucin (3), and citrinin (4) have been isolated from the marine-derived fungus Microsporum sp. The structure and absolute stereochemistry of a new compound (1) was assigned on the basis of physicochemical data. Compounds 1—3 exhibited a significant radical scavenging activity against 1,1-diphenyl-2-picrylhydrazyl (DPPH) with IC50 values of 14.2, 11.3, and 11.5 μM, respectively, which are more potent than the positive control, ascorbic acid (IC50, 20 μM). Compound 1 also showed a moderate antibacterial activity against the methicillin-resistant and multidrug-resistant Staphylococcus aureus (MRSA and MDRSA) with MIC value of 50 μg/ml.