Two Different Pathways Leading to Phenanthrenes and 9,10-Dihydrophenanthrenes of the Genus Dioscorea

Phenanthrene Biosynthesis, Bibenzyl Synthase, Batatasins, D ioscoreaceae The bibenzyl batatasin III was formed de novo in aerial bulbils and tubes o f D ioscoreaceae from dihydro-m-coumaric acid. In cell-free preparations, bibenzyl synthase activity and an O-methyltransferase converting 3,3',5-trihydroxybibenzyl into batatasin III were detected. High rates o f incorporation o f dihydro-m-coumaric acid into a 9 ,10-dihydrophenanthrene (hircinol) showed that a pathway being known to occur in orchids is also effective in Dioscoreaceae. The biosynthesis o f hircinol could be stimulated by infecting the aerial bulbils with various fungi. In parallel to the dihydro-w-coumaric acid pathway another biosynthetic reaction sequence leading to phenanthrenes was found to occur. The pathway was established in its principal steps: /7-coumaric acid trihydroxystilbene (resveratrol) — phenanthrene (batatasin I or iso-batatasin I).