HPLC Analysis of fusaric, 9,10-dehydrofusaric and their methyl esters, toxic metabolites from weed pathogenic Fusarium species

A simple and rapid HPLC method, using a high-density C18 column, has been developed for the quantitative analysis of fusaric and dehydrofusaric acids and their methyl esters in the methanol extract of lyophilised culture filtrates of species of Fusarium. The method has been used to determine the content of these metabolites in two strains of Fusarium oxysporum and in strains of F. nygamai and F. udum. Fusaric acid has been isolated and identified from a strain of F. udum for the first tim

Relation between in vitro production of ascosonchine and virulence of strains of the potential mycoherbicide Ascochyta sonchi: a method for its quantification in complex samples

The potential of the Ascochyta sonchi fungus as a mycoherbicide for biol. control of the perennial weeds Sonchus arvensis and Cirsium arvense was studied. Ascosonchine, an enol tautomer of 4-pyridylpyruvic acid with potential herbicidal properties, is the main phytotexin produced by the fungus. A simple and sensitive method was developed for rapid quant. anal. of ascosonchine by HPLC with UV detection. The ascosonchine toxin contents in culture filtrates of 9 strains of A. sonchi were measured. The tested strains produced up to 2.7 mg ascosonchine/L when grown in static conditions for 4 wk. The toxin prodn. by each fungal strain was compared with the virulence on the host weed plant to det. if the most virulent strains could be selected by choosing the best toxin producers. The results did not support this assumption. The HPLC method was also used to quantify toxin prodn. under different fungal growth conditions to achieve the highest toxin prodn. The most productive fungal strain produced >8 mg/L when grown in static conditions for 8 wk

Drazepinone, a trisubstituted tetrahidronaphthofuroazepinone with herbicidal activity produced by Drechslera siccans

When grown in a minimal-defined medium, a strain of Drechslera siccans, a pathogenic fungus isolated from seeds of Lolium perenne, produced phytotoxic metabolites. This strain is one of the best toxin producers among several grass-pathogenic fungal strains collected and tested to find phytotoxins to be used as natural herbicides of monocot weeds. From the culture filtrates of D. siccans, we isolated a new phytotoxic trisubstituted naphthofuroazepinone, named drazepinone, and characterized it as a 3,5,12a-trimethyl-2,5,5a,12a-tetrahydro-1H-naphtho[2',3':4,5]furo[2,3-b]azepin-2-one. Assayed at 2 g L-1 soln. the novel metabolite proved to have broad-spectrum herbicidal properties, without antibacterial and antifungal activities, and low zootoxic activity. Its original chem. structure and the interesting biol. properties make drazepinone a potential natural herbicide

Ascaulitoxin, an unusual phytotoxic bis-amino acid N-glucoside from Ascochyta caulina

A new unusual phytotoxic bis-amino acid N-glucoside, named ascaulitoxin, was isolated from the culture filtrate of Ascochyta caulina, the causal agent of leaf and stem necrosis of Chenopodium album, a promising mycoherbicide for the biological control of this common noxious weed. Ascaulitoxin, characterized by extensive use of NMR techniques and chemical methods as N2- (2,4,7-triamino-5-hydroxy)-octanedioyl-β-D-glucopyranoside, showed phytotoxic activity against host and non-host plants

Agropyrenol and agropyrenal, phytotoxins from Ascochyta agropyrina var. nana, potential herbicides for Elytrigia repens control

Elytrigia repens L. Desv. ex Nevski (commonly known as quack grass), is a perennial weed widespread through the cold temperate regions all over the world. It is managed only by chemical herbicides1,2 because it easily spreads by seed and rhizomes and produces allelopathic metabolites suppressing the growth of other plants. In surveys carried out with the aim to find pathogens of this species, which could have potential as biological agents for its control, a fungus was isolated from naturally diseased leaves of this species and identified as Ascochyta agropyrina (Fairman) Trotter var. nana Punith. Due to the interest of the authors in studying species belonging to the genus Ascochyta as sources of biologically active metabolites, a previous study led to the isolation of a main phytotoxin from the solid culture of this fungus and to its identification as papyracillic acid.3 On liquid medium A. agropyrina produces different toxins the main one of which, named agropyrenol, was characterized as a new disubstituted benzaldehyde on the basis of its chemical and spectroscopic properties. Other two new minor metabolites were isolated from the same culture and named agropyrenal and agropyrenone, respectively. They were characterized as a trisubstituted naphthalene carbaldehyde and a pentasubstituted 3H-benzofuranone, respectively. When assayed on leaves of some weedy plants, i.e. Mercurialis annua, Chenopodium album and Setaria viridis, agropyrenol proved to be phytotoxic, causing the appearance of necrotic lesions, agropyrenal was less active, while agropyrenone was inactive. None of compounds showed antibiotic, fungicidal or zootoxic activity. In this communication the production, isolation, and chemical and biological characterization of the metabolites produced by A. agropyrina var. nana in liquid culture will be illustrated and their potential as safe herbicides will be discussed