The isolation, chemical characterization and biological activity of two phytotoxic metabolites of Phomopsis helianthi Munt-Cvet et al., is reported. These compounds were identified by spectroscopic methods (UV, IR, 1H and 13 C NMR, and MS) as trans-4,6-dihydroxymellein (trans-3-methyl-4,6,8-trihydroxy-3-4-dihydroisocoumarin) and cis-4,6-dihydroxymellein (cis-3-methyl-4,6,8-trihydroxy-3,4-dihydrisocoumarin). This is the first report of the isolation of trans-4,6-dihydroxymellein from fungal cultures and of the production of cis- and trans-4,6-dihydroxymelleins by P.helianthi. Rice was found to be a good substrate for the production of the dihydroxymelleins. Culture extracts of some Italian and French strains of P.helianthi showed different degrees of phytotoxicity towards sunflower leaves and seedlings. The minimum effective doses of trans- and cis-4,6-dihydroxymelleins with different bioassays were 76 and 135 mg per spot (leaf puncture bioassay), 3 and 5 mmol g-1 fresh tissue (absorption by leaf cutting) and 5 and 2 mmol g-1 fresh tissue (absorption by cut cuttings), respectively. These compounds may contribute to the severity of the sunflower disease caused by P.helianthi.
Isolation and characterization of phytotoxic compounds produced by Phomopsis helianthi
TOSI, Laura;ZAZZERINI, Antonio;
1999
Abstract
The isolation, chemical characterization and biological activity of two phytotoxic metabolites of Phomopsis helianthi Munt-Cvet et al., is reported. These compounds were identified by spectroscopic methods (UV, IR, 1H and 13 C NMR, and MS) as trans-4,6-dihydroxymellein (trans-3-methyl-4,6,8-trihydroxy-3-4-dihydroisocoumarin) and cis-4,6-dihydroxymellein (cis-3-methyl-4,6,8-trihydroxy-3,4-dihydrisocoumarin). This is the first report of the isolation of trans-4,6-dihydroxymellein from fungal cultures and of the production of cis- and trans-4,6-dihydroxymelleins by P.helianthi. Rice was found to be a good substrate for the production of the dihydroxymelleins. Culture extracts of some Italian and French strains of P.helianthi showed different degrees of phytotoxicity towards sunflower leaves and seedlings. The minimum effective doses of trans- and cis-4,6-dihydroxymelleins with different bioassays were 76 and 135 mg per spot (leaf puncture bioassay), 3 and 5 mmol g-1 fresh tissue (absorption by leaf cutting) and 5 and 2 mmol g-1 fresh tissue (absorption by cut cuttings), respectively. These compounds may contribute to the severity of the sunflower disease caused by P.helianthi.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
