Ascosalipyrrolidinone A, an antimicrobial alkaloid, from the obligate marine fungus Ascochyta salicorniae

From the green alga Ulva sp., the endophytic and obligate marine fungus Ascochyta salicorniae was isolated. A. salicorniae was mass cultivated and found to produce the unprecedented and structurally unusual tetramic acid containing metabolites ascosalipyrrolidinones A (1) and B (2). Additionally, the new natural product ascosalipyrone (3) and the known metabolites 4 and 5 were obtained. Ascosalipyrrolidinone A (1) has antiplasmodial activity toward Plasmodium falciparum strains K1 and NF 54, as well as showing antimicrobial activity and inhibiting tyrosine kinase p56(lck).