Studies in the Synthesis of Hippuric Acid in the Animal Organism. Ii. the Synthesis and Rate of Elimination of Hippuric Acid after Benzoate

The question of the extent of the ability of the human organism to detoxicate benzoic acid by conjugation with glycocoll and elimination as hippuric acid in the urine has frequently been raised. Lewinsk? observed in the urine of men to whom 12 to 20 grams of benzoic acid had been given in small doses during t,he course of twelve hours, neither free benzoic acid nor benzoyl glycuronates. With larger doses of from 25 to 40 grams, small amounts (up to 26 per cent of the intake) of free benzoic acid were present in the urine, which was also dextro-rotatory and contained reducing substances, i.e., glycuronates. Thus with large doses, up to 20 grams of benzoic acid, the conversion to hippuric acid was found to be practically quantitative. Brugsch3 and Tsuchiya4 were unable to confirm the work of Lewinski and recovered only 22 to 48 per cent of the ingested benzoic acid (4 to 24.6 grams) as hippuric acid. Dakin5 found that benzoic acid taken by men in doses of 5 to 10 grams per day underwent a practically complete conversion to hippuric acid before elimination in the urine. No free benzoic acid could be detected in the urine. In none of these experiments was any difference between the free acid and the sodium salt observed.