Psoralen and other linear furanocoumarins as phytoalexins in Glehnia littoralis

Inoculation of Glehnia littoralis root slices with Pseudomonas cichorii induced the production of four linear furanocoumarin phytoalexins, psoralen, xanthotoxin, bergapten and demethylsuberosin, of which the former three have been reported as constituents of the crude drug Glehnia root. A time-course study on the respective P. cichorri-inoculated, UV-irradiated and non-irradiated root slices showed greatly increasing concentrations of the furanocoumarins after stress treatment. Psoralen, xanthotoxin and bergapten in the crude drug were considered, at least in part, to be stress metabolites produced during processing.