Sparticarpin: A Pterocarpan Phytoalexin from Spartium junceum

Although pterocarpan phytoalexins commonly ac­ cumulate in the fungus-inoculated tissues of papilionate legumes, only three compounds of this type possess oxygenation at C-2 [1, 2]. They are 2,3,9-trimethoxypterocarpan (1), 2,9-dimethoxy-3-hydroxypterocarpan (2-methoxymedicarpin, 2) and 2,3,9-trimethoxy-4-hydroxypterocarpan (3) all of which co­ occur with pisatin in the Fusarium solani f. sp. pisiinfected epicotyls of garden pea, Pisum sativum (Le­ guminosae, tribe Vicieae) [3, 4]. Compounds 1 3 have not been isolated from any other legume. We have recently discovered that detached leaflets of Spanish broom (Spartium junceum L.; tribe Genisteae) produce a phenolic pterocarpan phytoalexin (designated sparticarpin) following short wavelength UV irradiation or treatment with conidial suspen­ sions of the fungus Helminthosporium carbonum Ullstrup. In this paper we present evidence to show that sparticarpin is identical with 2,3-dimethoxy-9hydroxypterocarpan (4).