A new amino-substituted p-benzoquinone was isolated from the roots of Cynanchum wilfordii, together with the five known acetophenones: 2',5'-dihydroxyacetophenone, 4'-hydroxyacetophenone, 2',4' dihydroxyacetophenone, 4'-hydroxy-3'-methoxyacetophenone and cynandione A. The structure of new compound was elucidated as 2-acetyl-3,6-diamino-l,4-benzoquinone. © 1997 Elsevier Science Ltd