Effects of Lyophilization on the Metabonomic Phenotypes of Human Biofluids Characterized with NMR Analysis

Sample pretreatment is essential for metabonomic analysis. Lyophilization (freeze-drying) is widely used for sample pretreatment to remove solvent, especially water, prior to nuclear magnetic resonance (NMR) and/or mass spectrum (MS) analysis. However, the effects of lyophilization on metabonomic phenotypes remain to be fully investigated. In this study, NMR analysis was carried out to reveal the lyophilization-induced changes in metabonomic phenotypes of human urinary and serum samples. It was found that lyophilization resulted in large changes in the levels of some carboxylic acids and amino acids. Such effects were different between the urine and serum samples, perhaps indicating a biological matrix-dependent effect. The results of this study suggest that extra care and considerations should be taken when lyophilization is used for sample pretreatment and normalization in metabonomic analysis.