Plant Antimutagenic Agents, 5. Isolation and Structure of Two New Isoflavones, Fremontin and Fremontone from Psorothamnus fremontii

Two new isoflavones, fremontin and fremontone, were isolated from roots of Psorothamnus fremontii (Fabaceae), a desert plant. Compound 1 has the structure 5'-(alpha, alpha-dimethylallyl)-5,7,2',4'-tetrahydroxyisoflavone; compound 2 is similar but also contains the 3'-(gamma,gamma-dimethylallyl) substituent. The alpha,alpha-dimethylallyl substituent is rarely observed, and the combination of the alpha,alpha- and gamma,gamma-dimethylallyl substituents is unprecedented. Both 1 and 2 were nontoxic toward Salmonella typhimurium and were both highly active in the inhibition of mutagenicity of ethyl methanesulfonate (EMS) at all concentrations tested. Compound 2 was more active than 1 in the inhibition of mutagenicity of 2-aminoanthracene (2AN) and acetylaminofluorene (AAF) toward S. typhimurium.