Hexanoyl-lysine as an oxidative-injured marker - application of development of functional food.

We could proposed that N(ε)-(hexanoy)lysine, HEL, become a useful biomarker for detection of oxidative stress damage occurred by exhaustive exercise. We examined the preventive effect of flavonoid compound, eriocitrin, against exercise-induced oxidative damage in rat liver. Eriocitrin administration prior to exercise significantly suppressed the increases in thiobarbituric acid-reactive substance caused by lipid peroxidation during exhaustive exercise. The increase in the contents of HEL in rat liver was also abolished by eriocitrin administration. The concentration of oxidized glutathione was significantly increased by exercise, but the eriocitrin administration suppressed this increase. These results suggested that eriocitrin administration prior to exercise prevented oxidative damages caused by exhaustive exercise-induced oxidative stress. Therefore, it was suggested that HEL could be a good biomarker for oxidative stress, especially at earlier stage when oxidative damage was occurred by lipid peroxidation than a stage of harmful aldehyde formation. Moreover, it was suggested that eriocitrin metabolites, eriodictyol and 3, 4 - dihydroxyhydrocinnamic, might scavenge free radicals and reactive oxygen species, resulting in suppression of lipid peroxidation and reactive proteins with radicals to form HEL. These findings implied that eriocitrin might be useful as an anti-oxidative compound to protect oxidative stress damages.