β-Carotene and its physiological metabolites: Effects on oxidative status regulation and genotoxicity in in vitro models

Carotenoids are ubiquitously distributed in nature, beta-carotene being the most frequently found carotenoid in the human diet. In the human body, beta-carotene is absorbed, distributed and metabolized by enzymatic and/or nonenzymatic oxidant cleavage into several metabolites. Despite the broadly accepted biological value of beta-carotene, it has also been considered a double-edged sword, mainly due to its potential antioxidant versus prooxidant behaviour. In this sense, the aim of this work was to scrutinize the antioxidant or pro-oxidant potential of beta-carotene and its metabolites, namely trans-beta-apo-8'-carotenal and beta-ionone. Several parameters were evaluated in this study, viz. their effects on reactive species production, both in human whole blood and neutrophils; their effects on lipid peroxidation, in the absence and presence of peroxynitrite anion (ONOO-) or hydrogen peroxide (H2O2), using a synaptosomal model; and finally, their putative genotoxic effects in the human hepatic HepG2 cell line. In general, depending on the cellular model and conditions tested, beta-carotene and its metabolites revealed antioxidant effects to varying degrees without significant pro-oxidant or genotoxic effects.