A new dimeric 2-quinolone alkaloid, zanthobisquinolone, together with 15 known compounds, has been isolated from the root wood of Zanthoxylum simulans. On the basis of spectral analyses, the new alkaloid was elucidated as bis-(4-hydroxy-2-keto-1-methyl-3-quinolinyl)methylene. Among the isolates several furoquinoline alkaloids and N-acetylanonaine showed significant antiplatelet aggregation activity. © 1994.