A new benzo[c]phenanthridine, oxynorchelerythrine (1), and two new benzenoid derivatives, methyl 4-(2-hydroxy-4-methoxy-3-methyl-4-oxobutoxy)benzoate (2) and (E)-methyl 4-(4-((Z)-3-methoxy-3-oxoprop-1-enyl)phenoxy)-2-methylbut-2-enoate (3), have been isolated from the twigs of Zanthoxylum ailanthoides, together with 11 known compounds (4-14). The structures of these new compounds were determined through spectroscopic and MS analyses. Among the isolated compounds, decarine (4), (-)-syringaresinol (6), (+)-episesamin (8), glaberide I (9), (-)-dihydrocubebin (10), and xanthyletin (11) exhibited potent inhibition (IC50 values </= 4.79 microg/mL) of superoxide anion generation by human nutrophils in response to N-formyl-L-methionyl-L-leucyl-L-phenylalanine/cytochalasin B (fMLP/CB). Compounds 4, 8, and 11 also inhibited fMLP/CB-induced elastase release with IC50 values </= 5.48 microg/mL.