Carotenoids zeaxanthin

Chen, F. et al.. Isolation and purification of the bioactive carotenoid zeaxanthin from the microalga Microcystis aeruginosa by high-speed counter-current chromatography, J. Chromatogr, 1064, 183, 2005. 

Havaux, M. and W.I. Gruszecki. 1993. Heat- and light-induced chlorophyll a fluorescence changes in potato leaves containing high or low levels of the carotenoid zeaxanthin Indications of a regulatory effect of zeaxanthin on thylakoid membrane fluidity. Photochem. Photobiol. 58 607-614. 

Billsten HH, Sundstrom V, and Polivka T. 2005. Self-assembled aggregates of the carotenoid zeaxanthin Time-resolved study of excited states. Journal of Physical Chemistry A 109(8) 1521-1529. 

Organs n Carotenoids Zeaxanthin Crypto-Xanthin Lycopene a-Carotene (i-Carotene... 

The C10-dialdehyde 539 serves as the central olefination synthon in the preparation of the symmetrical carotenoid zeaxanthin 560 270). In this synthesis the phospho-nium salt 559 which can easily be prepared from the vinyl hydroxyionol 558 and triphenylphosphine hydrobromide, 504, is reacted with 539 in 1,2-epoxybutane, a solvent which seems to be especially suitable for Wittig reactions with polyene dialdehydes 270). The same phosphonium salt 559 was used in the synthesis of P-eryptoxanthin and zeinoxanthin. 

Phytochemical Content high in carotenoids (zeaxanthin, beta-cryptox-anthin, beta-carotene, lycopene), polyphenols (anthocyanins, ellagic acid)... 

Typical of many members of the botanical plant family Solanaceae, which also includes the tomato, eggplant, and pepper, goji is phytochemically rich, characterized by having both major classes of pigments—carotenoids and polyphenols, identified in laboratory research as having antidisease mechanisms. Goji appears to be one of the richest plant sources of the carotenoid zeaxanthin (closely related in chemical structure to the... 

In order to define the carotenoid structures necessary for LHCII assembly and stabilization, a number of different carotenoids have been used in reconstitution assays with only one carotenoid component present. Not only the xanthophyll cycle carotenoids zeaxanthin and antheraxanthin turned out to promote reconstitution but also heterologous carotenoids as diverse structurally as astaxanthin, okenone, and fucoxanthin. In general, a hydroxyl group in position 3 of at least one of the cyclohexane ring seems to be important for complex formation (D. Phillip, S. Hobe, A. Young, and H. Paulsen, unpublished). Similarly, the major LHCII from... 

There is much current debate about the relevance of such carotenoid repair processes to hydrocarbon carotenoids such as 8-carotene and lycopene in vivo where the parent carotenoid is unhkely to encounter the polar ascorbic acid. However, the cation radical, with a positive charge, maybe sufficiently polar and long-lived for such interactions to be possible. For the carotenoids found in the macula, where an efficient anti-oxidant process is crucial, the hydroxy carotenoids zeaxanthin, meso zeaxanthin and lutein are likely to be in a membrane orientation such that the corresponding cation radicals are efficiently repaired by the vitamin C (cf. vitamin E, below). 

Three such peroxyl radicals (9-phenanthrylperoxyl, 1-naphthylperoxyl and 2-naphthylperoxyl) have been studied in methanol and the rate constants obtained for their electron transfer reaction with the carotenoids zeaxanthin and lutein are given in Table 2. 

Two recent developments may be seen as significant with regard to the mechanistic details of qE. Firstly, it was found that low concentrations of ant. A (antimycin A), an inhibitor of ferredoxin-dependent cyclic electron transport, inhibit the development of qE completely whilst exerting little effect upon the magnitude of ApH. On the basis of this and other data, it was proposed that redox state, as well as ApH, is important in qE formation (6). Secondly, it has been propx sed that the carotenoid zeaxanthin, which is formed in LHC2 from violoxanthin in the light, plays a role in qE formation (7). 

In an excellent article by Bell et al. [356], the retention of 12 carotenoids (zeaxanthin, lutein, echinenone, / -cryptoxanthin, and a-, 9-cis-a-, 15-cis-a-, 9 -cis-a-, 13-cir-a-, ] -, 3-cis-P-, and 15-c/j- -caiotene) was studied with respect to temperature (277 K to 323 K) on C,g, C30, and C34 columns (A = 450 nm). Methanol was used as a mobile phase on the C g column and 95/5 methanol/methyl r-butyl ether on the C30 and C34 columns. The authors noted that acetonitrile was a potential mobile phase modifier but that high acetonitrile levels ofien led to decreases in recoveries. The use of dichloromethane was discouraged since residual HCI due to natural solvent degradation was implicated in poor recoveries as well. The latter is supported by the fact that low molecular weight alkenes are ofien used as preservatives in dichloromethane. A series of van t Hoff plots (essentially Infc vs. 1 /T) were presented where C]g phase showed near linearity and C30 and C34 phases exhibited nonlinear relationships for most carotenoids. 

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