Osteoclastogenesis Inhibitory Polyketides from the Sponge-Associated Fungus Xylaria feejeensis

A new ten-membered macrolide (1) and a new α-pyrone derivative, (-)-annularin C (2), together with 14 known analogs (3-16) were isolated from the AcOEt extract of the fungus Xylaria feejeensis isolated from the South China Sea sponge Stylissa massa. The structures of the new compounds were elucidated by the spectroscopic analysis and by comparison with reported data. The absolute configuration was determined by the optical rotation and ECD experiments. In an in vitro test, compounds 1, 5 and 9 exhibited significant down-regulating activity of osteoclast cell differentiation at 0.5 and 1 μm. This is the first report of the fungus X. feejeensis from a marine sponge and of osteoclastogenesis inhibitory activity for the metabolites of these kinds.