Isolation of balenine from opah (Lampris megalopsis) muscle and comparison of antioxidant and iron-chelating activities with other major imidazole dipeptides

•The first to extract pure balenine from opah muscles by hot water extraction, ion-exchange chromatography and recrystallization.•Balenine showed significantly higher antioxidant values and Fe(II) ion-chelating ability compared to 2 major imidazole dipeptides, carnosine and anserine.•In silico analysis showed that balenine have similar 3D structures to carnosine rather than anserine.•This study has suggested possible utilization of unused-resource of opah muscles as functional food ingredient. Balenine (Bal) in opah muscle was extracted using hot water and purified by ion-exchange chromatography and recrystallization to provide 41 g of over 95% pure Bal from 1 kg of opah muscle. The structure of purified Bal was identical to that of an authentic Bal standard by NMR analysis. The antioxidant (ORAC and HORAC values) and Fe(II) ion-chelating abilities of purified Bal were examined by comparison with two major imidazole dipeptides, carnosine (Car) and anserine (Ans). Opah-derived Bal showed significantly higher ORAC and HORAC values and Fe(II) ion-chelating ability at 0.3 mM. In silico molecular simulation revealed that Bal and Car formed hydrogen bonds between the hydrogen atom of the imidazole imino group and the carboxyl carbonyl oxygen, whereas Ans did not. The proposed method for extracting and purifying Bal from opah muscle suggests that opah can be utilized as a functional food or Bal resource.