New dibenzofurans from Phellinus ribis and their anti-inflammatory activity

Four previously undescribed dibenzofurans and derivatives, named ribisin G-J (1-4), along with seven known compounds (5-11) were isolated from Phellinus ribis. Among them, compounds 1-3 were identified as fully aromatic dibenzofurans, whereas compound 4 was a dibenzofuran derivative. Their structures were elucidated by comprehensive spectroscopic analysis. The absolute configuration of compound 4 was further confirmed by ECD calculation. The anti-inflammatory activity of all compounds was assessed in lipopolysaccharide (LPS)-induced RAW 264.7 macrophages. Notably, compound 4 exhibited inhibitory activity against nitric oxide (NO) production, with an IC₅₀ value of 12.23 ± 0.81 μmol·L^-1. Further studies revealed that compound 4 significantly inhibited the expression of IL-6, IL-1β and TNF-α.