Phytotoxic Metabolites Isolated from the Causal Agent of the Scabby Canker of Cactus Pear ( L.).

Six phytotoxins were obtained from the culture filtrates of the ascomycete , the causal agent of the scabby canker of cactus pear ( L.) in minor Sicily islands. The phytotoxins were identified as (-)-()-mellein (); (±)-botryoisocoumarin A (); (-)-(3,4)- and (-)-(3,4)-4-hydroxymellein ( and ); (-)-terpestacin (); and (+)-3,4-dihydro-4,5,8-trihydroxy-3-methylisocoumarin, which we named (+)-neoisocoumarin (). This identification was done by comparing their spectral and optical data with those already reported in literature. The absolute configuration (3,4) to (+)-neoisocoumarin () was determined using the advanced Mosher method. All six metabolites were shown to have phytotoxicity on the host (cactus pear) and non-host (tomato) plants, and the most active compounds were (±)-botryoisocoumarin A (), (-)-terpestacin (), and (+)-neoisocoumarin ().