Urinary Excretion of N¹-Menthyl-2-Pyridone-5-Carboxylic Acid and the Fate of remaining of Trigonellie

Abstract

During the development of a procedure for the determination of trigonelline (Tg) in human urine, an organic acid with a similar ultraviolet spectrum was isolated. The compound was found to be N¹-methyl-2-pyridone-5-carboxylic acid (Tg-2Py) (Lindenblad et al. 1956), which Holman et al. (1950) were unable to detected in normal human urine. Tg-2Py was determined by using high performance thin-layer chromatography (HPTLC), and the level of Tg-2Py excretion was about 1.5 times of Tg or N¹-methylnicotinamide(MNA) in 9 normal human urine (Yuyama et al, 1991). When Tg was orally administered in 3 human subjects, only 20% of the dose recovered in 24hr urine as unchanged Tg, and about 10% of the dose was converted into Tg-2Py (Yuyama et al. 1991). To explain the fate of missing Tg (60–70%),the possible mechanism for metabolism of Tg are as follows; 1) Tg may be metabolized further, expect Tg-2Py, 2) the ring fission could occur to pyridinium compounds, 3) Tg may be retained in the organ(s).