BIOSYNTHESIS OF PTEROCARPAN, ISOFLAVAN AND COUMESTAN METABOLITES OF MEDICAGO SATIVA: THE ROLE OF AN ISOFLAV-3-ENE

Article abstract of DOI:10.1016/S0031-9422(00)91023-9

Feeding experiments in CuCl2- and UV-treated lucerne (Medicago sativa) seedlings have shown that demethylhomopterocarpin-<6a-3H,Me-14C> is incorporated into vestitol and sativan without any loss of 3H label, and vestitol-<3-3H, Me-14C> is similarly incorporated into demethylhomopterocarpin and sativan with retention of the 3H:14C ratio.Thus, an isoflav-3-ene intermediate in the interconversion of demethylhomopterocarpin and vestitol is excluded. 7,2'-Dihydroxy-4'-methoxyisoflav-3-ene- was not incorporated into the three phytoalexins, but was an excellent precursor of 9-O-methylcoumestrol, as also was 7,2'-dihydroxy-4'-methoxyisoflav-3-en-2-one-.A biosynthetic pathway to coumestans via isoflav-3-enes and 3-arylcoumarins is proposed.A metabolic scheme in M. sativa interrelating eight classes of naturally occurring isoflavonoids is presented. - Key Word Index: Medicago sativa; Leguminosae; lucerne; biosynthesis; phytoalexin; pterocarpan; isoflavan; coumestan; demethylhomopterocarpin; vestitol; sativan; 9-O-methylcoumestrol.