E carotene

Traditionally, carotenoids have been given trivial names derived usually from the biological source from which they are isolated, but a semisystematic scheme has been devised that allows carotenoids to be named unambiguously and in a way that defines and describes their structure (Table 7.2). Specific names are based on the stem name carotene preceded by the Greek-letter prefixes that designate the two end groups. For example, 3-carotene is correctly referred to as p, p-carotene, and a-carotene as p, e-carotene. 

Luteine-5,6-epoxide (taraxanthin) 5,6-epoxy-5,6-dihydro-3,e-carotene-3,3 -diol... 

Animal tissues have yielded several carotenoids of previously unknown structure. Chiriquixanthins A and B from a yellow frog, Atelopus chiriquiensis, have been found to be epimeric e,e-carotene-3,3 -diols (18) and (19) differing... 

The Cso carotenoid decaprenoxanthin [2,2 -bis-(4-hydroxy-3-methylbut-2-enyl)-e,e-carotene (89)] has been prepared from the functionalized a-irone derivative (95), the synthesis of which is outlined in Scheme 1. In the mixture of (89) isomers formed, those with 2,6-trans end-groups predominated. 

Zeinoxanthin (3/ ,6 / )-/3,e-Caroten-3-ol Bicyclic, monohydroxy-carotenoid Inactive... 

The reaction of xanthophylls such as zeaxanthin (25), isozeaxanthin [j8,/S-carotene-4,4 -diol (78)], and lutein [)8,e-carotene-3,3 -diol (79)] with CHCI3-HCI... 

Optical Rotatory Dispersion and Circular Dichroism. O.r.d. data for several carotenoids have been tabulated.C.d. data have been recorded for astaxanthin (27 and 3S), /8,jS-carotene-2,3r3 -triol (6) and jS,/S-carotene-2,3,2, 3 -tetrol (7), decaprenoxanthin (37), the synthetic 2,2-dimethyl-e,e-carotenes (60) and (61)/ and the novel monocyclic C50 carotenoid (12). In the last case only very rough agreement was obtained between the observed spectrum and that calculated on the basis of the additivity hypothesis. ... 

Gerspacher. M., and Pfander. H.. C45 And Cjp-carotenoids. Synthesis of an optically active cyclic Cjq-building block and of decaprenoxanthine [(2E,6/f,2 /f,6 /f)-2,2 -frZ5(4-hydroxy-3-methylbut-2-enyl)-e.e-carotene], Helv. Chim. Acta, 72, 151, 1989. 

The occurrence of heat- and chemical-induced transformations of tryptophan and the nutritional and toxicologic consequences suggest a need for additional research to define possible approaches to prevent or minimize the formation of antinutritional and toxic tryptophan condensation and oxidation products in foods. The possible beneficial effects of antioxidants such as vitamins C and E, carotenes, flavonoids, indole derivatives, selenium compounds, and sulfur amino acids in enhancing the stability of tryptophan in foods need to be investigated. 

The syntheses of methyl bixin (24) and other natural carotenoids were mentioned above. A biogenetically inspired synthesis of e-carotene used the titanium tetrachloride complex of lycopene (16). Dehydrolycopene was also isolated. Two more syntheses of ) -carotene (2) have been reported which use intermediates in the synthesis of vitamin A (see Scheme 2). Although ll-cis-j5-carotene was produced it is rapidly isomerised to the all-frons form. The cross-conjugated system (72) has a previously unknown chromophore. Another example of this system, but with an additional 4 -oxo-group, was synthesised by Surmatis et al. in a study of the synthesis of keto carotenoids. They prepared echinenone (73) and the two protected 3,3 -dioxo-j8-carotene compounds (74) and (75). Treatment of the ketal with sulphuric acid gave mainly 3,3 -dioxo- -carotene (76) while hydrochloric acid gave 3,3 -dioxo-c-carotene (77). Under both conditions the enol ether gave the latter product. 

A lipoprotein particle has a shell composed of proteins (apolipoproteins) and a cholesterol-containing phospholipid monolayer (Figure 18-12). The shell is amphipathic because its outer surface is hydrophilic, making these particles water soluble, and its inner surface is hydrophobic. Adjacent to the hydrophobic inner surface of the shell is a core of neutral lipids containing mostly cholesteryl esters, triglycerides, or both. Small amounts of other hydrophobic compounds (e.g., vitamin E, carotene) also are carried in the lipoprotein core. 

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