Do Apo-Lycopenoids Have Antioxidant Activities In Vitro?

Lycopene is a predominant carotenoid in human plasma and may prevent degenerative diseases by antioxidant mechanisms. Moreover, not only lycopene itself, also its derived breakdown products, the apo-lycopenoids, could be responsible. Therefore, we analyzed the in vitro antioxidant activities of apo-60'-, apo-80'- and apo-12'-lycopenals, as well as of apo-10'-, apo-14'- and apo-11-series of lycopene (with terminal functions as alcohol, aldehyde, carboxylic acid, and ester) in various assays. We observed that the antioxidant activities, determined by measuring the ferric reducing antioxidant power (FRAP assay), the activities of bleaching 2,2'-azinobis-(3-ethylbenzothiazoline)-6-sulfonic acid (ABTS(center dot+)) and the activities to scavenge peroxyl radicals (LPSC assay), were often much lower compared to lycopene itself, as recently proposed by some authors. The antioxidant activities were strongly influenced by the length of the polyene chain and the type of terminal function as well. Considering our results and the low amounts of apo-lycopenals found in plasma as well as in lycopene-rich food products compared to (all-E)-lycopene we speculate that the effects of apo-lycopenoids as direct antioxidants in food samples as well as in blood and/or target tissues can be stated as negligible. Apo-lycopenoids may act as indirect antioxidants by activation of gene expression of antioxidant-derived enzymes.