Identification and measurement of methylamines in elasmobranch tissues using proton nuclear magnetic resonance ( 1 H-NMR) spectroscopy

Abstract

Methylamines are frequently present in high concentrations in biological samples, but their separation and quantification are difficult. Data presented show that methylamines commonly occurring in biological material can be uniquely identified and quantified by proton nuclear magnetic resonance spectroscopy by recording spectra at both neutral and acid pH. Use of a high sensitivity probe permits this analysis even in the presence of high water concentrations, allowing accurate quantification with minimum preparative technique. The method was tested on tissues of the dogfish. Trimethylamine oxide was found in amounts ranging from 42 mmol kg−1 fresh weight in liver, up to 115 mmol kg−1 fresh weight in heart. Betaine was found to range from 10 mmol kg−1 fresh weight in liver to 49 mmol kg−1 fresh weight in brain. Creatine was not found in heart or liver, but was present in body wall muscle and in brain. Further analysis using high-performance liquid chromatography allowed determination of urea/methylamine ratios, which ranged from 1.9 in liver to 3.7 in body wall muscle.