Phelligridimer A, a highly oxygenated and unsaturated 26-membered macrocyclic metabolite with antioxidant activity from the fungus Phellinus igniarius

[structure: see text] A highly oxygenated and unsaturated 26-membered macrocyclic metabolite, phelligridimer A (1), has been isolated from the Chinese medicinal fungus Phellinus igniarius. Its structure was elucidated by spectroscopic methods. A possible biogenesis of 1 mediated by the fungal metabolite hispidin was postulated. Phelligridimer A showed antioxidant activity (IC50 of 10.2 microM) but was inactive to several human cancer cell lines (IC50 > 50 microM) and enzymes PTP1B (IC50 > 25 microM) and thrombin (IC50 > 10 microM).