Inhibition of nitric oxide production in lipopolysaccharide-stimulated RAW264.7 macrophage cells by lignans isolated from Euonymus alatus leaves and twigs

The 80% methanolic extract of Euonymus alatus leaves and twigs afforded three new lignans, (−)-threo-4,9,4′,9′-tetrahydroxy-3,7,3′,5′-tetramethoxy-8-O-8′-neolignan (1), (−)-threo-4,9,4′,9′-tetrahydroxy-3,5,7,3′-tetramethoxy-8-O-8′-neolignan (2), (7R,8R,7′R)-(+)-lyoniresinol (3), together with seventeen known lignans (4-20). The structures of 1-20 were elucidated by extensive 1D and 2D spectroscopic methods including ¹H NMR, ¹³C NMR, ¹H-¹H COSY, HMQC, HMBC and NOESY. All the isolated compounds except for dilignans (19 and 20) significantly inhibited nitric oxide production in lipopolysaccharide-stimulated RAW264.7 cells.