Methylsulfonylmethane (MSM): A chemical shift reference for ¹ H MRS of human brain

We investigate the potential of a common dietary supplement, methylsulfonylmethane (MSM), to act as a chemical shift reference for in vivo ¹ H MR spectroscopy (MRS). The scope of the investigation is 2-fold: (1) We use high-resolution nuclear MR (NMR) measurements of the chemical shift values of MSM to establish the stability of MSM resonance across the ranges of pH and temperature, and (2) we demonstrate MR properties of MSM in the healthy human brain.

The relationship of chemical shift with temperature and pH is examined using high-resolution ¹ H NMR (14.1T) spectra of MSM in aqueous solution. MSM concentration in human brain tissue was measured as a function of time, together with the relaxation properties in the brain using ¹ H MRS at 3T.

The chemical shift of MSM remains stable in the range of the biologically relevant temperatures and pH values. The chemical shift at pH = 7.2 and 37°C was measured to be 3.142 ppm (relative to DSS, a common water-soluble NMR reference compound). Time course in the brain tissue in vivo confirmed an observable MSM signal 10 minutes after oral intake and a stable signal intensity within a ~3-hour window.

The chemical and biological properties of MSM-rapid crossing of the blood-brain barrier, water solubility, a singlet resonance resolved from metabolite resonances, chemical shift stability with respect to pH/temperature, and stable temporal presence in the brain-lead us to propose its use as a frequency reference for MRS.