CHEMISTRY OF THE SCROPHULARIACEAE .26. IRIDOID GLYCOSIDE UPTAKE BY CASTILLEJA-INTEGRA VIA ROOT PARASITISM ON PENSTEMON-TEUCRIOIDES

Castilleja integra was seeded in a pot of mature Penstemon teucrioides and allowed to grow to blossom stage as a root parasite on Penstemon. Aucubin, which is the major iridoid of the P. teucrioides root but which is normally lacking from C. integra, was isolated from the above-ground parts of the parasitic C. integra. The major iridoid glycosides of P. teucrioides leaves were aucubin, isoscrophularioside (10-0-cinnamylaucubin) and trans-eurostoside (10-0-p-hydroxycinnamylaucubin). The two cinnamyl esters from the leaves of P. teucrioides were not found in C. integra. This is the first demonstration of iridoid glycoside transmission from a root host plant to a parasitic plant.