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A substance that exhibited a tryptophan-like fluorescence peak at 354 nm on excitation at 295 nm at neutral pH was isolated from human urine. This compound was determined by visible-light absorption spectroscopy, fluorescence spectroscopy, 1H and 13C NMR spectros-copies, and FAB-MS to be 1-(1',2', 3', 4', 5'-pentahydroxypentyl)-1, 2, 3, 4-tetrahydro-2-carboline-3-carboxylic acid. This compound, named tetrahydropentoxyline, is a new type of hydrophilic tetrahydro-β-carboline, and its elution position was between those of 4-pyridoxic acid and kynurenic acid on C18 reversed-phase HPLC. The amount of tetrahydropentoxyline excreted in the urine of normal subjects [n = 21; age, 45 (SD 20) years] was about 5.2 (SD 1.0) mg per day.
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Horiuchi et al. (1994) studied this question.
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