BREFELDIN-A AND ALPHA,BETA-DEHYDROCURVULARIN, 2 PHYTOTOXINS FROM ALTERNARIA-ZINNIAE, A BIOCONTROL AGENT OF XANTHIUM-OCCIDENTALE

Alternaria zinniae, a fungus causing leaf necrosis in Xanthium occiden tale, a widespread noxious weed of Australian summer crops and pasture s, produces toxic metabolites when grown in liquid culture. Extensive application of NMR techniques, HR, EIMS and X-ray analysis permitted t he identification of brefeldin A (4H-cyclopent[f]oxacyclotridecin-4-on e-1,6,7,8,9,1 1a,12,13,14,14a-decahydro-1,13-dihydroxy-6-methyl) and a lpha,beta-dehydrocurvularin 3-dihydroxy-4-methyl-2H-3-benzoxacyclodode cin-2,10 (1H)-dione), two bioactive metabolites produced by a number o f fungal species belonging to the genera Alternaria, Ascochyta Penicil lium, Curvularia, Cercospora, and Phyllosticta, This is the first repo rt on the isolation of these two phytotoxins from A. zinniae. The inte resting semi-selective toxicity to X. occidentale is described here, a nd the possible use of fungus and toxins in integrated weed management programs is discussed. (C) 1998 Elsevier Science Ireland Ltd. All rig hts reserved.