Hydrocarbons carotenes

In contrast with the hydrocarbon carotenes primarily located in the cores of the CM particles, xanthophylls are present at the surfaces of the CM particles, making their exchanges with other plasma lipoproteins easier." Therefore, if some exchanges occur between lipoproteins, AUC (or absorption) values of the newly absorbed compound in the TRL fraction will be underestimated. Based on all these considerations, the present approach is more appropriate to determine the relative bioavailability of a compound derived from various treatments within one snbject and/or within one study. 

In fasting hnman sernm, the hydrocarbon carotenes (P-carotene and lycopene) are fonnd primarily in LDL, while the xanthophylls (Intein, zeaxanthin, and P-cryptox-anthin) are more evenly distribnted between LDLs and HDLs. As mentioned earlier and contrary to the carotenes, the xanthophylls are primarily located at the surfaces of lipoprotein particles, making them more likely to exchange between plasma lipoproteins. This hypothesis may explain their eqnal distribntion (or apparent equilibrinm) between LDLs and HDLs. 

Supercritical fluid extraction — During the past two decades, important progress was registered in the extraction of bioactive phytochemicals from plant or food matrices. Most of the work in this area focused on non-polar compounds (terpenoid flavors, hydrocarbons, carotenes) where a supercritical (SFE) method with CO2 offered high extraction efficiencies. Co-solvent systems combining CO2 with one or more modifiers extended the utility of the SFE-CO2 system to polar and even ionic compounds, e.g., supercritical water to extract polar compounds. This last technique claims the additional advantage of combining extraction and destruction of contaminants via the supercritical water oxidation process."... 

In normal-phase chromatography, polar components are more strongly retained than nonpolar components. Thus, hydrocarbon carotenes elute quickly while xanthophylls are retained and separated. This approach provides a more complete separation of polar carotenoids and their geometric isomers. This protocol is useful to the analyst that is specifically interested in the xanthophyll fraction of a sample. 

The complete separation from I-carotene to violaxanthin requires 35 min. Figure F2.3.4 illustrates the separation of carotenoids in a mixed food extract using this LC system. The hydrocarbon carotenes ( -carotene, a-carotene, lycopene) elute together at the solvent front. The elution order is fi-cryptoxanthin, u-cryptoxanthin, lutein, cis-lutein, zeaxanthin, cis-zeaxanthin, neoxanthin, and violaxanthin. 

While esterified xanthophylls can be extracted using solvent mixtures similar to those used for hydrocarbon carotenes, nonesterified xanthophylls are generally extracted using more polar solvents. For example, xanthophylls have been extracted from spinach using a mixture of methanol and tetrahydroftiran (Kopas-Lane and Warthesen, 1995). Acetone alone has also been used to extract lutein and zeaxanthin from a variety of fresh and processed vegetables (Updike and Schwartz, 2003). However, for the extraction of a wide range of carotenoids, a mixture of polar and nonpolar solvents works best. 

Van Berkel and Zhou first tested (3-carotene with ESI positive in 1994 (van Berkel and Zhou, 1994). In this study, a doubly charged molecular ion of (3-carotene was observed as the primary species when triflur-oacetic acid was present in the solution. Van Breemen was the first to utilize ESI as an interface between HPLC and MS to analyze carotenoids (van Breemen, 1995). In this study, ESI operated in negative mode ionized xanthophylls (astaxanthin, (3-cryptoxanthin, and lutein), but did not ionize hydrocarbon carotenes (lycopene and (3-carotene). In contrast, ESI positive produced only [M" ] for all carotenoids in this study, and the addition of halogenated solvents to the post-column effluent greatly enhanced signal intensity (van Breemen, 1995). A later study by Guarantini et al. demonstrated the ability of ESI positive to produce both [M" "] and [M + H]" " for a number of xanthophylls, and these authors attributed the production of the two species to solvent system... 

The carotenoids are a class of hydrocarbons (carotenes) and their oxygenated derivatives (xanthophylls) that consist of eight isoprenoid units joined in such a manner that the arrangement of the units is reversed at the center of the molecule, so that the two central methyl groups are in a 1,6-positional relationship and the remaining nonterminal methyl groups are in a 1,5-positional relationship. Their nomenclature has been standardized by lUPAC [http //www.chem.qmul.ac.uk/iupac/carot/], and their formal names are all based on the term carotene. ... 

Carotenoids are red and yellow fat-soluble pigments composed of a class of hydrocarbons (carotenes) and their oxygenated derivatives (oxycarotenoids or xanthophylls). The basic structure consists of eight isoprenoid units. A series of conjugated double bonds provides the characteristic chromophore. The basic structure can be modified by hydroxylation, hydrogenation, dehydrogenation, cyclization, or oxidation (Schwieter and Isler, 1967). Bacteria are capable of adding further isoprenoid units. 

Carotenoids are naturally occurring pigments synthesized as hydrocarbons (carotene, lycopene) or oxygenated derivatives (xanthophylls) by plants and microorganisms. Carotenoids have been successfully synthesized in several engineered strains [4, 85, 105—107]. Coexpression of GGPP synthase (crtE), phytoene synthase (crtB), and phytoenedesaturase crtl) is sufficient to convert IPP and farnesyl-diphosphate (FPP) to lycopene in . coli [106]. 

---