Postinfectional inhibitors from plants. XIII. Fungitoxicity of the phytoalexin, capsidiol, and related sesquiterpenes

Abstract

Capsidiol, the phytoalexin from peppers, rishitin, the phytoalexin from potatoes, and 20 other derivatives or model compounds related to capsidiol were compared for fungitoxicity against a range of pathogenic and non-pathogenic fungi, using spore germination and growth assay procedures. Capsidiol was the most active compound tested (mean effective dose (ED50) vs. Phytophthora infestons, 1 × 10−5 M) and all derivatives examined had decreased activity. No correlations were found between sensitivity to capsidiol or rishitin and pathogenicity for peppers or potatoes, nor were there any clear correlations between structure and activity. Activity was greatly influenced by minor structural changes and such changes frequently had differential effects on different fungi. The results suggest that phytoalexins such as capsidiol, even if not primary determinants of disease resistance, could influence the progress of disease and the sequence of subsequent colonization.