1H-NMR spectroscopic analysis of human urine: periodic variation of trimethylamine oxide excretion.

We used 1H-NMR to study the constituents of the urine from a female volunteer who had an unidentified complaint syndrome (chief complaints: discomfort of scapular region, abdominal distention and exhaustion). The pH dependence of the chemical shift of some constituents was investigated for signal assignments, and the intense peak at about 3.3 ppm was assigned to trimethylamine oxide (TMAO). We measured the concentration of the constituents of urine, and TMAO excretion in the urine over a three week time period. The TMAO excretion fluctuated in a cycle of about 2 days. The average excretion determined (3.8 mmole/day) is considerably higher than data of healthy humans that had been previously reported (0.3 to 0.5 mmole/day).