SEIRICARDINE-A, A PHYTOTOXIC SESQUITERPENE FROM 3 SEIRIDIUM SPECIES PATHOGENIC FOR CYPRESS

Isolated of Seiridium cardinale, S. cupressi (a Greek strain) and S. unicorne, three species associated with canker disease of cypress (Cupressus sempervirens) in the Mediterranean area, were found to produce phytotoxic substances in culture. Besides already known toxins (seiridin, iso-seiridin and seiricuprolide), four structurally related metabolites were found in small amounts in the culture filtrates of the three species. The major metabolite was characterized as a new bicyclic sesquiterpene, which we have called seiricardine A. The structures of the metabolite and of some key derivatives were established by spectral studies. When absorbed by severed twigs of cypress, a 0.3 mg ml-1 solution of seiricardine A produced leaf yellowing and browning. Subperidermal injection of a 0.1 mg ml-1 solution into young cypress trees caused necrotic lesions on the stem and a diffuse yellowing of adjacent twigs. In the agar diffusion assay, seiricardine A at concentration of 100-mu-g ml-1 showed a fungistatic effect on three test fungi.