Benzoylated Amino Acids in the Animal Organism. Iii. a Method for the Determination of Hippuric Acid* and a Study of the Synthesis of Hippuric Acid in Rabbits.? by Wendell H. Griffith

In 1877 Salkowski (1) noted the presence of a reducing substance in the urine of rabbits following the administration of sodium benzoate. Later Magnus-Levy (2) reported that this substance was benzoyl glycuronic acid and stated that less was found in the urine of rabbits than in the urine of dogs and sheep. At the present time it is the general assumption that rabbits detoxicate ingested benzoic acid almost entirely by conjugation with glycine and it has been the common practice to determine benzoyl glycine, or hippuric acid, by analyzing the urines for total combined benzoic acid. In a recent investigation of the effect of the administration of benzoate on the nitrogen partition in the urine of rabbits it was found that the undetermined nitrogen fraction, including hippuric acid nitrogen, was frequently less than the value for hippuric acid nitrogen calculated from the excretion of combined benzoic acid. It appeared from these analyses that there might be significant amounts of benzoyl glycuronic acid in the urines. A study was made, therefore, of the relative importance in rabbits of conjugation of benzoic acid with glycine and with glycuronic acid.