Through respective administrations of [1-14C] acetate, [3-14C] phenylalanine and [7-14C]-benzoic acid to Swertia japonica, it was proved that the biphenylcarboxylic acid moiety of the strongly bitter secoiridoid glucosides, amarogentin and amaroswerin existing in the plant, is biosynthesized from 3 units of acetates and 3-hydroxybenzoic acid formed from phenylalanine via benzoic acid.
