High-performance Isotope-Labeling Liquid Chromatography Mass Spectrometry for Investigating the Effect of Drinking Goji Tea on Urine Metabolome Profiling

Urine is a human biofluid that is widely used for metabolomics research on disease biomarker discovery. Ideally, the metabolome profiles generated from comparative groups of individuals should mainly consist of the endogenous human metabolites that reflect the healthy states of the individuals. However, external factors, such as diet, may alter the urine metabolome profile by either introducing a significant amount or variety of exogenous metabolites to urine or inducing changes of the metabolome profile. Thus, strict control of the external factors during the sample collection process is critical for urine metabolomics aimed at discovery of disease biomarkers. In this work, we describe a study to determine the effect of drinking Goji tea, which is considered a nutritional supplement drink in some regions of the world, on urine metabolome profile. The purpose of this work is not to determine the nutritional values of Goji tea, but to investigate whether drinking a moderate amount of Goji tea 1–3 h (short-term effect) or 12 h (longer-term effect) before urine collection can cause significant variations of urine metabolome profiles. A highly sensitive dansylation isotope labeling liquid chromatography mass spectrometry (LC-MS) method was used to determine the urine metabolomes before and after drinking Goji tea. From the studies of the short term (< 3 h) and longer term (12 h) effects of drinking Goji tea, it is clear that the consumption of a moderate amount of Goji tea does not affect the urine metabolome significantly. Fasting for 12 h should be sufficient to remove any potential interference of Goji metabolites from the human urine metabolome profile.