Biosynthesis of furocoumarins: further studies on Ruta graveolens.

The Authors have studied the biosynthesis of some furocoumarins contained in Ruta graveolens. Labeled 5,7- and 7,8-dihydroxycoumarins have been administered to the herb, however practically no incorporation of radioactivity was observed in the isolated furocoumarins. Moreover, with the aim to study in a more detailed way the role of rutaretin and marmesin, trapping experiments have been performed administering to the herb labeled umbelliferone together with unlabeled rutaretin and marmesin respectively. A very effective incorporation was observed into marmesin, in lesser extent into rutaretin. In trapping experiments carried out using labeled rutaretin together with unlabeled marmesin and “vice versa”, the results obtained clearly show that while marmesin was converted into rutaretin in a very effective way, rutaretin was transformed into marmesin only in a smaller extent. The Authors suggest the biogenetic origin of rutaretin and moreover formulate a new and more detailed aspect of the scheme for the biosynthetic pathway of furocoumarins in Ruta graveolens.