Concentricolide, an Anti-HIV Agent from the Ascomycete Daldinia concentrica

A novel benzofuran lactone, named concentricolide (=rel-(6R)-6-ethylbenzo[2.1-b:3,4-c']difuran-8(6H)-one; 1), was isolated along with four known compounds (friedelin, cytochalasin L-696.474, armillaramide, and russulamide) from the fruiting bodies of the xylariaceous ascomycete Daldinia concentrica. The structure of I was established by spectroscopic methods and X-ray crystallographic analysis. Its anti-HIV-1 activity was tested. Results showed that 1 inhibited HIV-1 induced cytopathic effects. The EC50 value was 0.31 mu g/ml. The therapeutic index (TI) was 247. Concentricolide exhibited the blockage (EC50 0.83 mu g/ml) on syncytium formation between HIV-1 infected cells and normal cells.