Seiricardine-b and Seiricardine-c, Phytotoxic Sesquiterpenes From 3 Species of Seiridium Pathogenic For Cypress

Seiricardines B and C, two tricyclic toxic sesquiterpenes, were isolated from culture filtrates of Seiridium cardinale, S. cupressi and S. unicorne, three fungi associated with canker disease of cypress (Cupressus sempervirens) in the Mediterranean area. These new toxic compounds are produced in addition to the already known toxins: seiridin, isoseiridin, seiricuprolide, cyclopaldic acid and seiricardine A. Seiricardine B and C are epimeric diastereomers; their structures and those of some key derivatives were established by spectral studies. Assayed on severed twigs of cypress, seiricardine B and C caused leaf chlorosis followed by browning, and chlorosis, respectively; whereas on tomato and bean cuttings they caused chlorosis and necrosis, and chlorosis, respectively. After injection of seiricardine B and C into cortical tissues of young cypress plants, a hypertrophic reaction of the tissues adjacent to the site of injection and a reddish discolouration of distal leaves, and a reddening and longitudinal lesions, respectively, were observed. In the antimicrobial assay, seiricardine B, in comparison to seiricardine C, showed a higher inhibitory effect on mycelial growth of three test fungi.