Phelligridimer A, a Highly Oxygenated and Unsaturated 26-Membered Macrocyclic Metabolite with Antioxidant Activity from the Fungus Phellinus igniarius

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 μM) but was inactive to several human cancer cell lines (IC₅₀ > 50 μM) and enzymes PTP1B (IC₅₀ > 25 μM) and thrombin (IC₅₀ > 10 μM).