Production and metabolism of 6-methoxymellein in cultured carrot cells

The carrot phytoalexin, 6-methoxymellein, accumulated in carrot suspension culture when it was incubated with a partial hydrolysate of carrot cells obtained by pectinase or trypsin treatment. 6-Methoxymellein also accumulated when these enzymes were added to the culture. In both cases, phytoalexin content decreased rapidly after maximum accumulation was attained, suggesting that the cultured carrot cells metabolized the phytoalexin.

Cultured carrot cells incubated with the phytoalexin formed three different metabolites: among them, two which accumulated in the medium, were identified as the β-glucoside of 6-methoxymellein and 6-hydroxymellein.

6-Methoxymellein was found to be toxic to the host plant and induced a lag period in the growth of cultured carrot cells at low concentration. When it was added at concentrations higher than 0·5 mm, it caused a rapid decrease in viable cell number.