Carotenoids detection

The relationship between serum and tissue concentrations of lutein and zeaxanthin was recently studied by Johnson et al, (2000). Dietary intake of xanthophyll-rich vegetables (for example, spinach and com) resulted in significant increases in lutein concentration in serum, adipose tissue and buccal cells, and this correlated with changes in MP density. However, P-carotene and lycopene are normally the major carotenoids detected in buccal cells (Peng et al, 1994). 

Hartmann et al. 1996). The gN component is often too weak to observe. The Ni(I) EPR signals were not detected upon 350 nm irradiation of Ni-MCM-41 samples before adsorption of carotenoids. Detected at 9 GHz, EPR signals of an isolated Ni(I) species with =2.09 provide direct evidence for the reduction of Ni(II) ions by carotenoids. 

Fig. 8.3 UPLC analysis of Cupi/cMm-lyoplrilizEd pericarp carotenoids. Carotenoids detected by absorption at 454 nm, following separation on a waters acquity C18 1.8 xm HSS particle, 2.1 x 100 mm column resolved with 10% isopropanol (v/v) (a) and 100% acetonitrile (b). The solvent profile included two linear phases (0-3 min at 75% (b) 3-11 min from 95 to 100%) flow rate of 0.75 mL/min. (a) Standards (each at 100 ppm) capsorubin (1.7 min), capsanthin (2.08 min), antherxanthm (2.69 min), zeaxanthin (2.97 min), f -cryptoxanthin (4.86 min), and P-carotene (8.15 min), (b) Valencia pericarp extract, (c) NuMex Sunset pericarp extract...

Ermakov, I.V. Gellermann, W. 2010. Validation model for Raman based skin carotenoid detection. Arch. Biochem. Biophys. 504 40 9. 

Lutein is also the major carotenoid in kiwi fruit, red seedless grapes, zucchini squash and pumpkin, while zeaxanthin is the major carotenoid in orange pepper. 3-Cryptoxanthin is also distributed in foodstuffs such as broccoli and green grapes, and is one of the major carotenoids detectable in human blood. 

More specific methods involve chromatographic separation of the retinoids and carotenoids followed by an appropriate detection method. This subject has been reviewed (57). Typically, hplc techniques are used and are coupled with detection by uv. For the retinoids, fluorescent detection is possible and picogram quantities of retinol in plasma have been measured (58—62). These techniques are particularly powerful for the separation of isomers. Owing to the thermal lability of these compounds, gc methods have also been used but to a lesser extent. Recently, the utiUty of cool-on-column injection methods for these materials has been demonstrated (63). 

Several studies have investigated the role of dietary factors in prostate cancer risk, but results appear inconsistent. Significant effects have not been detected for dietary soya products certain vegetables, beans, fruit, rice and seaweed appear to be protective in some studies, while another has shown no protective effect from seaweed or vegetable consumption. In addition, a number of other risk factors have been shown to be associated with an increased risk of this cancer, including meat and dairy products and carotenoids. 

Because the carotenoids favour hydrophobic domains they are generally localised in the membranes and lipoproteins of animal cells. In this location they can influence the oxidation of membrane lipids and prevent the passage of free radicals from one cellular compartment to another. Thus, DNA in the nucleus is protected from intracellularly generated ROS by (at least) the nuclear membrane and from extracellular ROS by a number of membranes. Should ROS reach the nucleus, base oxidation can occur. The base most susceptible to oxidation is guanine, although all other bases can also be affected. The cell has the ability to detect damaged bases, excise them. 

In the carotenoid radicals, the unpaired electron is highly delocalized over the conjugated polyene chromophore. This has a stabilizing effect and also allows subsequent reactions. The cation and anion radicals can be detected by their characteristic spectral properties, with intense absorption in the near-infrared region. 

More than 600 carotenoids have been isolated from natural sources, but only about 60 have been detected in the human diet — about 20 in human blood and tissues. P-Carotene, a-carotene, lycopene, lutein, and P-cryptoxanthin are the five most prominent carotenoids present in the human body. 

Aside from isomerization, transformation of the 5,6-epoxy to the 5,8-furanoid group is a common alteration during heating treatments of carotenoids. Violaxanthin was found to be the major carotenoid in mangoes however, in commercially processed mango juice, violaxanthin was not detected while auroxanthin, not present in the... 

Muller, H., Determination of the carotenoid content in selected vegetables and fruit by HPLC and photodiode array detection, Z. Lebensm. Enters. Forsch. A, 204, 88, 1997. 

APCl in positive mode ionization and triple quadrupole detection was used for determination of free and bound carotenoids in paprika, obtaining the [M + H]+ and losses of fatty acids as neutral molecules from the [M + H]+ with MeOH, MTBE, and H2O as eluent from the C30 column. The positions of the fatty acids on unsymmetrical xanthophylls could not be established by the MS data. 

Cortes et al.. Identification and quantification of carotenoids including geometrical isomers in fruit and vegetable juices by liquid chromatography with ultraviolet-diode array detection, J. Agric. Food Chem., 52, 2203, 2004. 

Rentel, C. et al.. Silver-plated vitamins a method of detecting tocopherols and carotenoids in LC/ESI-MS coupling. Ana/. Chem., 70, 4394, 1998. 

Figure 4.7 shows the structures of important carotenoids (all-E) lutein, (all-E) zeaxanthin, (all-E) canthaxanthin, (all-E) p-carotene, and (all-E) lycopene. Employing a self-packed C30 capillary column, the carotenoids can be separated with a solvent gradient of acetone water=80 20 (v/v) to 99 1 (v/v) and a flow rate of 5 pL min, as shown in Figure 4.8 (Putzbach et al. 2005). The more polar carotenoids (all-E) lutein, (all-E) zeaxanthin, and (all-E) canthaxanthin elute first followed by the less polar (all-E) p-carotene and the nonpolar (all-E) lycopene. Figure 4.9 shows the stopped-flow II NMR spectra of these five carotenoids. The chromatographic run was stopped when the peak maximum of the compound of interest reached the NMR probe detection volume.

In summary, NMR spectroscopy is an extremely versatile tool useful that enables researchers to understand the structure of natural products such as carotenoids. For a full structural assignment, the compound of interest has to be separated from coeluents. Thus, it is a prerequisite to employ tailored stationary phases with high shape selectivity for the separation in the closed-loop on-line LC-NMR system. For the NMR detection, microcoils prove to be advantageous for small quantities of sample. Overall, the closed-loop system of HPLC and NMR detection is very advantageous for the structural elucidation of air- and UV-sensitive carotenoids. 

The recognition of the importance of MP in maintaining the health of the retina has led to the development of a number of methods for determining its concentration in situ. These methods, necessarily noninvasive, are routinely employed in dietary supplementation studies with lutein or zeaxanthin to monitor the uptake of the carotenoids into the retina. Every method exploits the optical properties of lutein and zeaxanthin, specifically their absorbance at visible wavelengths. The detection of a light signal, modified by the carotenoids, is accomplished either by the retinal photoreceptors themselves (psychophysical methods) or by a physical detector such as a photomultiplier,... 

Application of Resonance Raman Spectroscopy to the Detection of Carotenoids In Vivo... 

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