Development of a quantitative method for analyzing three imidazole dipeptides using high-performance liquid chromatography and its application for meat and fish

Imidazole dipeptides (IDPs) such as anserine, balenine, and carnosine are functional peptides that are expected to improve cognitive functions and have antioxidant properties. However, there are few methods to extract these three representative IDPs from foods with high-efficiency and analyze them simultaneously using simple, rapid, and accurate high-performance liquid chromatography (HPLC). In this study, an analysis method was developed based on the combination of an internal standard, an extraction reagent, and HPLC conditions for the quantification of IDPs. IDPs in foods were extracted using 8 % perchloric acid solution with 4-imidazoleacrylic acid added as an internal standard; the IDPs were then analyzed by isocratic elution using an amino column. IDPs in nine types of meat and fish were quantified. The recovery and the quantification ranges of IDPs on the established method were 97.4 %–103.3 % and 0.78 μM–200 μM, respectively. The results showed that the amounts of balenine, anserine, and carnosine were extremely high in whale, salmon, and pork, respectively. Interestingly, venison contained the three IDPs, and the ratio of anserine to carnosine (balenine:anserine:carnosine = 1:4:5) was similar, which differed in other animal meats. This method can be used effectively, particularly for the quantification of foods containing these three IDPs.