The urinary excretion of mandelic acid administered intravenously to cats.

MANDELIc acid, when administered to animals, may be recovered almost quantitatively from the urine. Moreover, when mandelic acid appears in the body as the result of metabolic processes, it is supposed to be excreted without further change [Knoop, 1905; Dakin, 1922; Quick, 1928]. Neubauer [1909], Neubauer & Fischer [1910], Neubauer & Gross [1910] and Neubauer & Warburg [1910] claimed that after giving r-phenylaminoacetic acid to dogs by mouth and perfusing dog livers, the following substances could be recovered from the urine and perfusate: (-)C6H5. CH(NH2) . COOH. (-)C06H5.CH(OH).COOH (examined after crystallization from benzene). C6H5.CO. COOH. C6H5CO .NHCH2 . COOH (presumably from C6H15. COOH). When, however, (-)phenylaminoacetic acid was given to dogs in similar fashion it appeared in the urine largely unchanged, while (+ )phenylaminoacetic acid was metabolized with relative ease. Both benzoylformic acid and (-)mandelic acid were recovered from the urine in the latter case. When benzoylformic acid was administered to dogs, (-)mandelic acid appeared in the urine. r-Mandelic acid, when given by mouth, was practically all recovered in the urine as such, showing, if anything, a slight dextrorotation, there being a mere trace of benzoylformic acid. In man the results were the same as in the dog, but in rabbits administration of r-phenylaminoacetic acid by mouth gave rise to urinary excretion of optically pure (-)phenylaminoacetic acid, benzoylformic acid, hippuric acid, but no mandelic acid. Neubauer therefore argued that mandelic acid could not be an intermediary between phenylaminoacetic acid and benzoylformic acid. He also believed that (+)phenylaminoacetic acid, the form attacked in the body, could not yield (-)mandelic acid directly because of stereochemical dissimilarity. This latter conclusion is, however, untenable, since Clough [1918] showed that (+ )phenylaminoacetic acid has the same stereochemical configuration as (-)mandelic acid. Neubauer put forward the following scheme for the metabolism of phenylb aminoacetic acid: C6H15. CH(NH2) .COOH -0C6H5.CO.COOH -÷ (-)CSH, .CH(OH). COOH. oxidative deamination asymmetric reduction