Phytotoxic nonenolides produced by fungi pathogenic for crops and weeds

Pinolidoxin, 2-hexadionoyloxy-7-hydroxy-9-propyl-5-nonen-9-olide, is the first phytotoxic nonenolide, isolated from some of us on 1993, together three minor ones as the main toxin produced by Ascochyta pinodes.1 This is the fungal causal agent of pea anthracnose. Successively, phytotoxic nonenolide as putaminoxin, the main one, the close related putaminoxins B-D were also isolated from Phoma putaminum, the fungus proposed as mycoherbicide to biological control Erigeron annuus, a widespread weed in the pasture of northern emisphere.2 Later, stagonolide, a new nonenolide, was also isolated as the main toxin from liquid culture of Stagonospora cirsii proposed for the biological control of Cirsium arvense and Sonchus arvensis, two very noxious perennial weeds of several agrarian crops, essentially cereals. Successively nine related new nonenolides were isolated together to the well known modiolide A, from solid cultures of the same fungus.3 So that some studies were carried out using the toxins some their natural analogues and hemisynthetic derivatives to carry out studies on the structure-activity relationships and on their mode of action.4 Recently, from a strain of Ascochyta pinodes isolated in Spain from infected pea and grown in liquid culture were isolated herbarumin II, and 2-epi-herbarumin II together with a new nonenolide, named pinolide. In this communication an overview on the phytotoxic fungal nonenolides will be illustrated as well as the chemical and biological characterization of pinolide and the potential practical application of some of them as natural eco-friendly herbicides.