The organic extract of the fungus Alternaria cichorii, a pathogen of Russian knapweed, was analyzed. A series of zinniol-related compounds with varying degrees of phytotoxicity have been isolated for the first time from the organic extract of a pathogenic fungus. The structures of all of the compounds, which include cichorine, zinniol, and the four novel compounds zinfiimidine, Z-hydroxyzinnimidine, zinnol and zinndiol, were determined by spectroscopic methods.