Abstract
β-Carotene (BC) is the most abundant carotenoid in human diet, almost solely as (all-E)-isomer. Significant amounts of (Z)-isomers of BC are present in processed food as well as in mammalian tissues. Differences are described for the activity of various BC isomers in forming retinal and protecting against cancer and cardiovascular diseases. Eccentric cleavage of BC leads to degradation products such as carotenals. A variety of negative consequences were published for the non-vitamin A active BC metabolites, such as inducing the carcinogenesis of benzo[a]pyrene, impairing mitochondrial function, or increasing CYP activity. To increase the knowledge on the antioxidant activity, a variety of BC isomers and metabolites were tested in various in vitro assays.In the present study, no ferric reducing activity (FRAP assay) was observed for the BC isomers. Between the major BC isomers (all-E, 9Z, and 13Z) no significant differences in bleaching the ABTS●+ (αTEAC assay) or in scavenging peroxyl radicals (ROO●) generated by thermal degradation of AAPH (using a chemiluminescence assay) were detected. However, the (15Z)-isomer was less active, maybe due to its low stability. The degradation to β-apo-carotenoids increased FRAP activity and ROO● scavenging activity compared to the parent molecule. Dependence on chain length and character of the terminal function was determined in αTEAC assay with following order of increasing activity: β-apo-8’-carotenal < β-apo-8’-carotenoic acid ethyl ester < 6’-methyl-β-apo-6’-carotene-6’-one (citranaxanthin). The results indicate that BC does not lose its antioxidant activity by degradation to long chain breakdown products.
Highlights
Carotenoids are a widespread group of naturally occurring fat-soluble colorants
The results indicate that blood carotenoids. β-Carotene (BC) does not lose its antioxidant activity by degradation to long chain breakdown products
The authors speculated that these results provide strong evidence that BC breakdown products are responsible for the occurrence of carcinogenic effects found in the Alpha-Tocopherol Beta-Carotene Cancer prevention (ATBC) study and the β-Carotene and Retinol Efficacy (CARET) Trial
Summary
Carotenoids are a widespread group of naturally occurring fat-soluble colorants. 80-90% of the carotenoid intake comes from fruit and vegetable consumption. Of the more than 700 naturally occurring carotenoids identified far, approx. Β-Carotene (BC) is a naturally occurring orange-colored carbon-hydrogen carotenoid, abundant in yellow-orange fruits and vegetables and in dark green, leafy vegetables [2]. Only six of them (β-carotene, β-cryptoxanthin, α-carotene, lycopene, lutein and zeaxanthin) account for more than 95% of total blood carotenoids. It is the most widely distributed carotenoid in foods [3].
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