Dimethyl sulfone in human cerebrospinal fluid and blood plasma confirmed by one‐dimensional 1 H and two‐dimensional 1 H‐ 13 C NMR

1 H‐NMR spectroscopy at 500 MHz was used to confirm that a previously unidentified singlet resonance at 3.14 ppm in the spectra of cerebrospinal fluid and plasma samples corresponds to dimethyl sulfone (DMSO 2 ). A triple resonance inverse cryogenic NMR probe, with pre‐amplifier and the RF‐coils cooled to low temperature, was used to obtain an 1 H‐ 13 C HSQC spectrum of CSF containing 8 µ M (753 ng/ml) DMSO 2 . The 1 H‐ 13 C correlation signal for DMSO 2 was assigned by comparison with the spectrum from an authentic reference sample. In plasma and CSF from healthy controls, the concentration of DMSO 2 ranged between 0 and 25 µmol/l. The concentration of DMSO 2 in plasma from three of four patients with severe methionine adenosyltransferase I/III (MAT I/III) deficiency was about twice the maximum observed for controls. Thus, DMSO 2 occurs as a regular metabolite at low micromolar concentrations in cerebrospinal fluid and plasma. It derives from dietary sources, from intestinal bacterial metabolism and from human endogenous methanethiol metabolism. Copyright © 2005 John Wiley & Sons, Ltd.