Isoflavone biosynthesis in Onobrychis viciifolia: Formononetin and texasin as precursors of afrormosin

4,2′,4′-Trihydroxychalcone- carbonyl-¹⁴C], formononetin- Me-¹⁴C] and texasin- Me-¹⁴C] were all good precursors of afrormosin (7-hydroxy-6,4′-dimethoxyisoflavone) in Onobrychis viciifolia seedlings, and a biosynthetic pathway involving these intermediates is proposed. 2′,4′-Dihydroxy-4-methoxychalcone- carbonyl-¹⁴C] and daidzein-carbonyl-¹⁴C] were poor precursors. Incorporations into formononetin were also recorded.