AUTHOR=Kawakami Hiroko , Itakura Yuki , Yamamoto Tetsuya , Yoshiya Taku 

TITLE=Cyclic homodimer formation by singlet oxygen-mediated oxidation of carnosine

JOURNAL=Frontiers in Chemistry

VOLUME=12

YEAR=2024

URL=https://www.frontiersin.org/journals/chemistry/articles/10.3389/fchem.2024.1425742

DOI=10.3389/fchem.2024.1425742

ISSN=2296-2646

ABSTRACT=<p>Although carnosine (β-Ala-L-His) is one of physiological protectants against <italic>in vivo</italic> damages caused by reactive oxygen species (ROS), its reactivity against singlet oxygen (<sup>1</sup>O<sub>2</sub>), an ROS, is still unclear at the molecular level. Theoretically, the reaction consists of two steps: i) oxygenation of the His side chain to form an electrophilic endoperoxide and ii) nucleophilic addition to the endoperoxide. In this study, the end product of <sup>1</sup>O<sub>2</sub>-mediated carnosine oxidation was evaluated using 2D-NMR and other analytical methods both in the presence and absence of external nucleophiles. Interestingly, as the end product without external nucleophile, a cyclic homodimer was confirmed under our particular conditions. The reaction was also replicated in pork specimens.</p>