Terpestacin, a toxin produced by Phoma exigua var. heteromorpha , the causal agent of a severe foliar disease of oleander ( Nerium oleander L.).

Since 1987, several cytochalasins were isolated from Phoma exigua var. heteromorpha , the causal agent of foliar blight disease of oleander ( Nerium oleander L.), and chemically and biologically characterised. During the purification process of a large-scale production of cytochalasins A and B, necessary to continue the study on their anticancer activity, a metabolite having a different carbon skeleton compared to that of cytochalasans, was isolated. It was identified as terpestacin, a well-known toxic fungal stestertepenoid, isolated for the first time from P. exigua var. heteromorpha , by spectroscopic investigation (essentially 1D and 2D ¹ H and ¹³ C-NMR and ESI MS) and optical methods in comparison with the literature data. Terpestacin and some its derivatives (including a natural one, fusaproliferin) were prepared and tested for their biological activity. Terpestacin and fusaproliferin had some inhibitory effects on seed germination of Phelipanche ramosa , whereas none of the compounds caused phytotoxic effects on weed leaves.[Formula: see text].