Structures, Biogenesis, and Biological Activities of Pyrano[4,3-c]isochromen-4-one Derivatives from the Fungus Phellinus igniarius

Further chemical investigation of the Chinese medicinal fungus Phellinus igniarius has resulted in the isolation and structural elucidation of three pyrano[4,3-c]isochromen-4-one derivatives, phelligridins H (1), I (2), and J (3), together with the known compounds davallialactone (4), scopolin, nebularine, uridine, trehalose, glucitol, and ethyl glucoside. The structures of 1-3 were elucidated by spectroscopic methods. Phelligridins H (1) and I (2) possess unprecedented carbon skeletons, and phelligridin J (3) is an oxidative derivative of the co-occurring phelligridin A. Compounds 1 and 2 inhibited protein tyrosine phosphatase 1B (PTP1B) and rat liver microsomal lipid peroxidation, while compound 3 exhibited cytotoxic activity against several human cancer cell lines.