Effect of heat-processing on the antioxidant and prooxidant activities of β-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 β-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 β-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 μM. At 100 μM, 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 β-carotene but longer treatments made BCC prooxidant, showing that samples that underwent drastic extraction processes could not tolerate additional steps for functional food production.