LC–MS/MS analysis of desmosine and isodesmosine in skipjack tuna “Katsuo” elastin

To achieve the precise quantitation of desmosine (DES) and isodesmosine (IDS) in skipjack tuna “Katsuo” elastin, an isotope dilution liquid chromatography tandem mass spectrometry (LC–MS/MS) method was applied for the samples of elastin-containing products in tablet, drink, jelly, and capsule forms, and the results were compared with data obtained from an amino acid (AA) analyzer. The quantity of DES/IDS was found to be ca. 2860 mg/kg for elastin peptide A, and 1690 mg/kg for elastin peptide B. Thus, the DES/IDS ratio of 100 ± 5% was obtained for the LC–MS/MS values compared to the data provided by the (AA) analyzer excepting jelly and capsule. This work justifies the quantification of DES/IDS in elastin products by LC–MS/MS, contributing to its application in the agro-food industry.