RAPID METABOLISM OF ISOFLAVONOIDS IN ELICITOR-TREATED CELL-SUSPENSION CULTURES OF PUERARIA-LOBATA

Upon treatment with yeast extract as an elicitor to cell suspension cultures of Pueraria lobata, the constitutive isoflavonoid conjugates (7-O-glucoside-6 ''-O-malonyl esters) showed a rapid decline in their contents within 4 hr, followed by both reaccumulation of the conjugates and formation of isoflavones. Simultaneous treatment of a potent translation inhibitor, cycloheximide (200 mu M), could not suppress the elicitor-inducible decrease of the preexisting isoflavonoids, although it resulted in almost complete inhibition of both reaccumulation of the conjugates and formation of isoflavones. Exogenously applied C-14-labelled isoflavones were readily converted to their respective malonyl glucosides in the cells, When yeast extract was applied to the cell cultures in which [C-14]-daidzein had been incorporated into its malonyl glucoside, the methanol-soluble radioactivity decreased rapidly within 4 hr and it was not recovered for 48 hr, indicating that most of the conjugate was incorporated into an insoluble cell wall fraction. The rapid response upon elicitation was selective for isoflavonoids and not for flavonoids.