Quantitative Analysis of Biomarkers to Distinguish Between Korean and Chinese Mud Loaches

Mud loach (<i>Misgurnus mizolepis</i>) is a freshwater fish widely farmed in inland aquaculture owing to its nutritional value. However, failure to distinguish Chinese from Korean mud loach negatively affects the distribution economy and food safety regulation. Untargeted profiling was previously used to determine the origin of mud loaches, and N-acetylhistidine and anserine were selected as biomarker candidates. However, their quantitative verification and practical applicability for origin discrimination have not been thoroughly investigated. In this study, mud loaches of different geographical origins were analyzed using liquid chromatography-ultraviolet and liquid chromatography-tandem mass spectrometry to quantify the two metabolites, followed by statistical and receiver operating characteristic (ROC) analyses to evaluate their discriminative performance. Compared with Korean mud loaches, Chinese mud loaches showed significantly higher concentrations of both metabolites. The area under the curve values for N-acetylhistidine and anserine were 0.88 and 0.89, respectively, reflecting high sensitivity and specificity for discriminating between Korean and Chinese mud loaches. Cutoff values were established for reliably distinguishing the geographical origin of mud loaches. The established approach based on N-acetylhistidine and anserine can be used to determine the geographical origin of mud loach.