Selected cis/trans isomers of carotenoids formed by bulk electrolysis and iron(III) chloride oxidation
- 1 January 1997
- journal article
- research article
- Published by Royal Society of Chemistry (RSC) in Journal of the Chemical Society, Perkin Transactions 2
- No. 4,p. 783-786
- https://doi.org/10.1039/a605027a
Abstract
Bulk electrolysis and chemical oxidation with FeCl3 of all-trans canthaxanthin (I) and 8′-apo-β-caroten-8′-al (II) gave primarily the 9- and 13-cis-isomers, which were separated by HPLC and identified by 1H NMR spectroscopy. Optical absorption measurements showed that the 15-cis, 9,13-di-cis isomers of I are also formed by these methods. In the case of the unsymmetrical compound II, additional isomers were formed. The cis isomers account for about 40–60% of products formed. Formation of the isomers is believed to occur by rotation about certain bonds in the cation radicals or dications, which are formed in the oxidation processes. The neutral cis species are then formed by an electron exchange reaction of the cis-cation radicals with neutral all-trans carotenoids in solution. The electrochemical and iron(III) chloride oxidation induced isomerization are shown to be efficient and improved methods for forming selected carotenoid isomers.Keywords
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