Carotene oxidized

Falconer, M.E. et ah. Carotene oxidation and off-flavor development in dehydrated carrot, J. Sci. Food Agric., 15, 857, 1964. 

Interestingly, early examples of carotenoid autoxidation in the literature described the influence of lipids and other antioxidants on the autoxidation of carotenoids." " In a stndy by Budowski et al.," the influence of fat was fonnd to be prooxidant. The oxidation of carotenoids was probably not only cansed by molecnlar oxygen bnt also by lipid oxidation products. This now well-known phenomenon called co-oxidation has been stndied in lipid solntions, in aqueons solntions catalyzed by enzymes," and even in food systems in relation to carotenoid oxida-tion." The inflnence of a-tocopherol on the antoxidation of carotenoids was also stndied by Takahashi et al. ° who showed that carotene oxidation was snppressed as... 

A similar system, but with a more hindered porphyrin (tetramesitylporphyrin = tetraphenylporphyrin bearing three methyl substituents in ortho and para positions on each phenyl group), was tested for P-carotene oxidation by molecular oxygen. This system was chosen to slow the oxidation process and thus make it possible to identify possible intermediates by HPLC-DAD-MS analysis. The system yielded the same product families as with lycopene, i.e., (Z)-isomers, epoxides, and P-apo-carotenals, together with new products tentatively attributed to diapocarotene-dials and 5,6- and/or 5,8-epoxides of P-apo-carotenals. The oxidation mechanism appeared more complex in this set-up. 

Takahashi, A., Shibasaki-Kitakawa, N., and Yonemoto, T., A rigorous kinetic model for beta-carotene oxidation in the presence of an antioxidant, alpha-tocopherol, J. Am. Oil Chem. Soc., 80, 1241, 2003. 

The product distribution resulting from P-carotene oxidization by 02 was studied by Stratton et al. (1993) using reverse-phase HPLC, UV-vis spectrophotometry, and mass spectrometry. The oxidation products were identified as [3-ionone, P-apo-14 -carotenal, (i-apo-IO -carotenal, P-apo-8 -carotenal, and P-carotene-5,8-endoperoxide. The formation of 5,8-endoperoxide derivative by a [4+2] Diels-Alder addition mechanism was also reported in the 02-mediated oxidation of P-carotene in reverse micelles (Montenegro et al. 2002), P-ionone (Borsarelli et al. 2007), and of the A1E retinoid derivative (Jockusch et al. 2004). 

As mentioned previously, P-carotene oxidation products substantially reduce mitochondrial activity in an RPE cell line, 28 SV4, derived from fetal human RPE cells (Hurst et al., 2005). In these experiments P-carotene was degraded in dichloromethane/methanol/water solution by hypochlorite, NaOCl. Exposure of the 28 SV4 cells to a mixture of the degradation products corresponding... 

Marques, SA, Loureiro, APM, Gomes, OF, Garcia, CCM, Di Mascio, P, and Medeiros, MHG, 2004. Induction of l,N-2-etheno-2 -deoxyguanosine in DNA exposed to beta-carotene oxidation products. FEBS Lett 560, 125-130. 

In spite of a high reactivity of 3-carotene in free radical reactions and marked antioxidant effects in in vitro systems, 3-carotene did not show itself as an effective in vivo antioxidant. Furthermore, recent clinical trials suggested that the administration of 3-carotene may be useless or even harmful to patients with heart and some other diseases, especially to smokers. One might suspect that one of the major reasons of toxic in vivo effects of 3-carotene might be the formation of prooxidative compounds during 3-carotene oxidation. In contrast to... 

Effect of Cysteine-Fe-NO Complex on Llnoleate-/3-Carotene Oxidation"... 

Retinal] (carotene) Oxidation of Vitamin A (Retinol), in turn derived from pro-vitamin A carotenes PKC... 

The destruction of p-carotene during lipid peroxidation is readily observed by bleaching of the carotene color (44). Presumably, p-carotene oxidation is initiated by H-abstraction, and such a mechanism has been proposed for the cooxidation of carotenoids during the lipoxygenase catalyzed oxidation of polyunsaturated fatty acids (45), as shown by Reaction Q. 

The simplest prototype of carotenes, called I/-carotenes, is the polyunsaturated acyclic hydrocarbon (15Z)-7,8,11,12,7, 8, llM2 -octahydro- r, Ir-carotene, known as phytoene, which is synthesised from two molecules of geranylgeranyl diphosphate. Isomerisation of phytoene yields the trans-isomer phytofluene (7,8,1 l,12,7, 8 -hexahydro- Ir, Ir-carotene). Oxidation of phytofluene gradually gives -carotene (7,8,7, 8 -tetrahydro-vIf,vIf-carotene), neurosporene (7,8-dihydro- f, Ir-carotene) and lycopene(vIf,vIr-carotene), which is the final product of the biosynthesis (9-180) and the main pigment of tomatoes (30-200 mg/kg), watermelons (33 121 mg/kg) and rose hips (101-834 mg/kg... 

Oxidation of these compounds subsequently gives rise to 5,6-epoxides, such as antheraxanthin (9-183) derived from P-carotene or taraxanthin (lutein epoxide) derived from a-carotene. Oxidation... 

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