Max Vecchi

Astaxanthin and its metabolites in wild rainbow trout (Salmo gairdneri R.)

Abstract 1. 1. The unusual intensely red exterior pigmentation of four wild rainbow trout, caught in an alpine lake of Austria, prompted quantitative and qualitative analysis of carotenoids in skin and flesh. 2. 2. Emphasis was laid on the absolute configuration of the hydroxycarotenoids. 3. 3. (3S,3′S- Astaxanthin was the main pigment in skin and flesh besides some yellow xanthophylls, which in skin were β-adonixanthin, (3R,3′S,6′R)- epilutein and (3R,3′R)- zeaxanthin and in flesh, lutein and zeaxanthin. 4. 4. The results are compared with data obtained in farmed rainbow trout fed unlabelled and tritiated astaxanthin enantiomers. 5. 5. The vitamin A1 (retinol) and A2 (dehydroretinol) statuses in liver were determined.

Applications of high-pressure liquid chromatography and gas chromatography to problems in vitamin A analysis

Abstract Some results obtained by gas chromatography and high-pressure liquid chromatography in vitamin A analysis are given. In particular, it was demonstrated that high-pressure liquid chromatography surpasses gas chromatography as an analytical tool for this application.

Physicochemical Properties and Assay of the Tocopherols

Publisher Summary This chapter focuses on physicochemical properties and assay of the tocopherols. The tocopherols, all of which possess vitamin E activity, may be regarded as tocol derivatives, methyl-substituted (I) on the benzene ring. With the exception of 5-methyltocol, all methyltocols are found in naturc, as are also two tocotrienols, with the attributed structure. The tocopherols are liposoluble compounds, liquid at room temperature. The tocopherols possess three asymmetrical carbon atoms (C-2, C-4ʹ, C-8ʹ), so that eight optical isomers are possible. The configuration in the side chain (C-4ʹ and C-8ʹ) is possibly that of phytol, the absolute configuration. Several methods, physical and chemical, have been proposed for the estimation of the tocopherols. The proper estimation is usually preceded by separation to eliminate interfering substances or to separate the individual tocopherols. Chromatographic methods of separation are of major importance for the analysis of tocopherols for two reasons: (1) The most important quantitative method of determination, that of Emmerie and Engel, and all other methods based on the reducing properties of the tocopherols, are unspecific. (2) The biological activity of the individual tocopherols differs considerably. Quantitative assay of tocopherols, therefore, requires that the extracts be purified beforehand to remove other reducing substances and that the mixture be separated into the individual tocopherols.

The gas chromatographic determination of ascorbic acid in the form of its trimethylsilyl ether derivative

Abstract A method of determining vitamin C by gas chromatography by means of its silyl ether derivative has been investigated. N-Trimethylsilylacetamide proved a suitable silylating agent. Analysis by mass spectrometry demonstrated formation of the tetra-(trimethylsilyl ether) of ascorbic acid. Kinetic studies and analysis by gas chromatography indicate that the reaction proceeds almost quantitatively. The results are well reproducible.

High-performance liquid chromatographic separation and proton nuclear magnetic resonance identification of the 6-mono-cis and 6,6′-di-cis isomers o rhodoxanthin

Abstract The separation by high-performance liquid chromatography of the all- trans , the 6-mono- cis and the 6,6′-di- cis -isomers from synthetic samples o rhodoxanthin is described. The structures of the cis isomers are deduced by 1 H nuclear magnetic resonance (NMR) at 400 MHz, including several homonuclear Overhauser 1 H NMR experiments and, in part, by 13 C NMR at 100 MHz.

RECENT ADVANCES IN THE SYNTHESIS AND ANALYSIS OF 3,4-OXYGENATED XANTHOPHYLLS

Abstract The progress made within the last three years in the synthesis and analysis of astaxanthin and of other related 3,4-oxygenated xanthophylls is reviewed. This includes preparatively attractive routes to all optical isomers of adonirubin, 3-hydroxy echinenone, and of adonixanthin. (3R,3′R)-, (3S,3′S)-, as well as meso-(3R,3′S)-astaxanthin could be separated by HPLC when (3RS,3′RS)-astaxanthin (a 1:1 mixture of race-mate and meso-form) was first converted into the corresponding diaste-reomeric di-(-)-camphanates. The usefulness of this accurate analytical method for the separation of optical isomers of astaxanthin was demonstrated by the analysis of various astaxanthin samples from different natural sources. Surprisingly, some of these were found to be mixtures of the three optical isomers. The extension of this separation technique to other 3-hydroxy-4-oxo carotenoids provided, in combination with spectroscopic data, an excellent analytical method for the determination of the constitution, chirality and purity of these carotenoids.