Isolation and characterization of limonoate and nomilinoate A-ring lactones.

A method combining solid-phase extraction and reversed-phase high-performance liquid chromatography is described for the isolation of two key metabolites in the limonoid biosynthetic pathway critical to citrus quality. Potassium salts of limonoate A-ring lactone and nomilinoate A-ring lactone were isolated from young Chandler pummelo seedlings and characterized on the basis of proton and carbon NMR data.