Canthaxanthin studies

Sujak, A., K. Strzalka, and W.I. Gruszecki. 2007b. Thermotropic phase behaviour of lipid bilayers containing carotenoid pigment canthaxanthin A differential scanning calorimetry study. Chem. Phys. Lipids 145 1-12. 

The Davies pulsed ENDOR spectrum of canthaxanthin oxidized on silica-alumina measured in the temperature range of 3.3-80K showed no lineshape changes, which is in agreement with previous 330 GHz EPR studies of canthaxanthin radical cations (Konovalova et al. 1999). This implies very rapid rotation of the methyl groups down to 3.3 K. 

Konovalova, T. A., J. Krzystek et al. (1999). 95-670GHz EPR studies of canthaxanthin radical cation stabilized on a silica-alumina surface. J. Phys. Chem. B 103 5782-5786. 

Piekara-Sady, L., S. A. Jeevarajan et al. (1993). An ENDOR study of canthaxanthin cation radical in solution. Chem. Phys. Lett. 207 173-177. 

In fact, Everett et al. (1995, 1996) have reported the scavenging of N02 by 3-CAR, and their results indicate that the reaction proceeds via electron transfer only and no radical addition occurs. The electron transfer was shown to proceed with a rate constant of 1.1 x 108 M 1 s 1 in tcrt-butanol/ water mixtures (50% v/v). This study was extended by the same workers (Mortensen et al. 1997) to include five other carotenoids, with canthaxanthin (CAN) having the lowest rate constant of reaction with N02 (1.2 x 107 M 1 s-1), and LYC having the second highest (1.9 x 107 M 1 s-1) after ZEA (2.1 x 107 M 1 s-1). All the rate constants obtained were an order of magnitude below that for 3-CAR. However, the experiments were carried out in 60 40%, v/v tert-butanol/water mixture (80 20%, v/v for LYC due to aggregation) rather than the 50% (v/v) mixture used for 3-CAR and the N02" was generated in a different way. 

Studies in humans and animals suggest that carotenoid absorption depends on several factors including vitamin A status. Sklan and others (1989) demonstrated that vitamin A supplementation reduced (3-carotene and canthaxanthin absorption in chickens. Dietary carotenoids absorption and bioconversion to vitamin A varied inversely with the vitamin A status of Philippine children (Ribaya-Mercado and others 2000). Some studies (Lecomte and others 1994 Albanes and others 1997) have suggested a possible negative effect of alcohol consumption on carotenoid absorption however,... 

The carotenoids, trans-3 carotene (Sigma), I canthaxanthin (Fluka), II 3-8 -apocarotenal (Fluka), III and crocetin (Sigma), IV were used in this study (see structure). Of the above four carotenoids, only crocetin is water soluble. The porphyrins 5,10,15,20-tetra-phenyl-21H,23H-porphine (TPP) and 5,10,15,20-tetra-(4-sodiumsulfonato-phenyl)-21H,23H-porphine, TPPS were obtained from Aldrich, TPPS is a water soluble porphyrin. Carotenoids I-III were used as supplied, however crocetin was purified according to published methods (15) just prior to use. 

Carotenoid Metabolism and Metabolites. A scheme has been proposed for the metabolism of /3-carotene by the stick insect Carausius morosus to give /3,/8-caroten-2-ol (20) and /3,/3-carotene-2,2 -diol (21) via intermediate 2-oxo-compounds such as (27)." " Feeding experiments have shown that in the goldfish lutein [ S, -carotene-3,3 -diol (150)] and zeaxanthin are converted into astaxanthin (60) whereas /8-carotene and canthaxanthin (130) are not. Further studies suggest that marine red fish such as sea bream cannot oxidize the 3- and 4-positions of the /8-ring. 

Many studies have been conducted on the volatile thermal degradation products of carotenoids. Several authors have reported the formation of toluene and xylene as TDP of bixin and capsanthin (18) and B-carotene (10, 11, 18-25), as well as canthaxanthin (26). 

Miscellaneous Physical Chemistry. A kinetic study has been made of the electrochemical reduction of /8-carotene. The photoelectron quantum yield spectrum and photoelectron microscopy of /3-carotene have been described. Second-order rate constants for electron-transfer reactions of radical cations and anions of six carotenoids have been determined. Electronic energy transfer from O2 to carotenoids, e.g. canthaxanthin [/8,/3-carotene-4,4 -dione (192)], has been demonstrated. Several aspects of the physical chemistry of retinal and related compounds have been reported, including studies of electrochemical reduction, the properties of symmetric and asymmetric retinal bilayers, retinal as a source of 02, and the fluorescence lifetimes of retinal. Calculations have been made of photoisomerization quantum yields for 11-cis-retinal and analogues and of the conversion of even-7r-orbital into odd-TT-orbital systems related to retinylidene Schiff bases. ... 

N.M.R. Spectroscopy. The effects of lanthanoid shift reagents on the H and C n.m.r. spectra of canthaxanthin (90) have been studied in detail. Chemical shifts and signal broadening showed that the metal binds the carbonyl group at two sites. A computer programme was used to study the conformation of canthaxanthin. Similar studies" have been performed with a -trans-, 9-cis-, 11-CW-, and 13-c/s-retinal and 8 -apo-/3-caroten-8 -al (165), A high-resolution... 

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