Effect of heat-processing on the antioxidant and prooxidant activities of beta-carotene from natural and synthetic origins on red blood cells

Extraction of bioactives is a cause of structural changes in these molecules. In this work, the bioactivity of commercial natural beta-carotenes, one softly extracted without heat-assistance from Momordica cochinchinensis (BCG), one conventionally extracted from another natural source (BCC), and a synthetic one (BCS), was assessed during an additional heat-treatment mimicking formulation. Their antioxidant activities were evaluated after heat-treatment at different concentrations through hemolysis of horse red blood cells. The thermal 15-cis-isomerization of beta-carotene, characterized by DAD-HPLC, resulted in a 2.5- to 4.8-fold increase in the anti-hemolytic effect but this was undetected in chemical assay, at 4 mu M. At 100 mu M, BCC lost its antioxidant properties and became pro-oxidant. This effect might be caused by long-chain-oxidized-products of BCC. Results demonstrated that a short heat-treatment improves the bioactivity of beta-carotene but longer treatments made BCC prooxidant, showing that samples that underwent drastic extraction processes could not tolerate additional steps for functional food production. (C) 2015 Elsevier Ltd. All rights reserved.