Biogenesis of linear O-alkylfuranocoumarins: A new pathway involving 5-hydroxymarmesin

Abstract adioactivity from [ 3 H] 5-hydroxymarmesin was incorporated into 5-methoxypsoralen by administration to leaves of Ficus carica and cut ends of Ruta graveolens . No other furanocoumarins were labelled. Trapping experiments, in which [ 3 H]marmesin together with 5-hydroxymarmesin was administered to fig leaves and to cut ends of rue, provided good evidence that 5-hydroxymarmesin is formed by hydroxylation of marmesin. These results, together with those obtained previously with 8-hydroxymarmesin demonstrate that, in addition to the pathway which involves the hydroxylation of psoralen, the O -alkylfuranocoumarins are also formed by a pathway which involves the hydroxylation of marmesin.