Cathepsin B inhibitory tetraene lactones from the fungus Talaromyces wortmannii.

Wortmannilactones E–H (1–4), four new cathepsin B inhibitors, were produced and isolated from the culture of the soil filamentous fungus Talaromyces wortmannii. Their structures and relative configurations were elucidated on the basis of 1D- and 2D-NMR techniques, three of them (1, 2, and 4) posses an oxabicyclo[2.2.1]heptane moiety. Compounds 1–4 showed inhibitory activities against cathepsin B with IC50 values of 4.3, 6.5, 13.0, and 6.0 μM, respectively.