Anti-influenza virus polyketides from the acid-tolerant fungus Penicillium purpurogenum JS03-21.

Fractionation of the ethyl acetate extract of an acid-tolerant fungus, Penicillium purpurogenum JS03-21, resulted in the isolation of six new compounds, purpurquinones A-C (1-3), purpuresters A and B (4 and 5), and 2,6,7-trihydroxy-3-methylnaphthalene-1,4-dione (6), together with three known compounds, TAN-931 (7), (-)-mitorubrin (8), and orsellinic acid. The structures of 1-6 were elucidated primarily by NMR experiments. The absolute configurations of 1-4 were assigned on the basis of CD and NOESY data. Compounds 2-4 and 7 exhibited significant antiviral activity against H1N1, with IC50 values of 61.3, 64.0, 85.3, and 58.6 μM, respectively.