Anti-Inflammatory Phenolic Metabolites from the Edible Fungus Phellinus baumii in LPS-Stimulated RAW264.7 Cells

The edible fungus Phellinus baumii Pilat (Hymenochaetaceae) has been used in Korean traditional medicines for strengthening health and prolonging life. An extract of the fruiting bodies of P. baumii was subjected to bioassay-guided fractionation based on its anti-inflammatory effects in lipopolysaccharide (LPS)-stimulated RAW264.7 cells. The resulting fractions were chemically investigated, leading to isolation of three phenolic compounds (1–3), a sesquiterpene (4), two steroids (5–6), a fatty acid (7), and a cerebroside (8). Spectroscopic analyses including 1D and 2D NMR spectroscopy and LC/MS were used to determine their chemical structures. Compounds 2, 4, 5, 7 and 8 were identified in P. baumii for the first time. Since all compounds were isolated from active fractions with anti-inflammatory activity, their ability to inhibit LPS-stimulated nitric oxide (NO) production in RAW264.7 cells were evaluated in vitro. Compounds 1, 2, 3, 5 and 7 inhibited LPS-stimulated NO production, and compounds 1–3 had IC₅₀ values <10 μM. Treatment of LPS-stimulated RAW264.7 cells with compounds 1–3 inhibited phosphorylation of IKKα and IκBα. In addition, treatment of compounds 1–3 reduced LPS-induced increases of nuclear factor-kappa B (NF-κB) p65, iNOS and COX-2 protein expressions. Collectively, compounds 1–3 inhibited NF-κB-dependent inflammation in RAW264.7 cells. Thus, P. baumii is a potential source of natural anti-inflammatory agents, and active compounds 1–3 could be promising lead compounds for the development of novel anti-inflammatory agents.