Carotenoids characteristics

Reactions at the C-1,2 double bond of lycopene 4.123) leads to a series of acyclic carotenoids characteristic of photosynthetic bacteria, or by cyclization to the mono- and bi-cyclic carotenoids typical of plants. Cyclization is believed to be initiated by protonation at C-2 and to proceed as shown in Scheme 4.27 the three ring types, P, e... 

Yokohama Y, Kageyama A, Ikawa T and Shimura S (1977) A carotenoid characteristic of Chlorophycean seaweeds living in deep coastal waters,... 

Carotenoids have two general characteristics of importance to the food iadustry they are not pH sensitive ia the normal 2—7 range found ia foods, and they are not affected by vitamin C, making them especially important for beverages. They are more expensive than synthetic food dyes and have a limited color range. In their natural environment they are quite stable, but they become more labile when heated or when they are ia solution. Under those conditions, there is a tendency for the trans-double bonds to isomerize to the cis-stmcture with a subsequent loss of color iatensity. The results of controlled tolerance and toxicity tests, usiag pure carotenoids, iadicate that they are perfecdy safe as food colors (132). 

Salatrim is a mixture of many triglycerides that have the characteristics mentioned above. Because it is partially absorbed, Salatrim does not have the problems associated with Olestra. It does not have any laxative effects nor does it prevent the absorption of fat-soluble vitamins and carotenoids. 

The carotenoids are the most widespread group of pigments in nature, with an estimated yield of 100 million tonnes per annum. They are present in all photosynthetic organisms and responsible for most of the yellow to red colours of fruits and flowers. The characteristic colours of many birds, insects and marine invertebrates are also due to the presence of carotenoids, which have originated in the diet. Animals are unable to synthesise carotenoids de novo, and so rely upon the diet as the source of these compounds. Carotenoids found in the human diet are primarily derived from crop plants, where the carotenoids are located in roots, leaves, shoots, seeds, fruit and flowers. To a lesser extent, carotenoids are also ingested from eggs, poultry and fish. Commercially, carotenoids are used as food colourants and in nutritional supplements (Table 13.1). Over recent years there has been considerable... 

Fruits are yet more prodigious than flowers in their synthetic abilities. More than 70 characteristic carotenoids have been described and classified as those with minimal quantities, higher quantities, and specific carotenoids, for example, capsan-thin and capsorubin in pepper fruits. 

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. 

Carotenoids are predominantly synthesized in nature by photosynthetic plants, algae, bacteria, and some fungi. - Animals can metabolize carotenoids in a characteristic manner, but they are not able to synthesize carotenoids. The total global biosynthesis of carotenoids is estimated to be in excess of 100 million tons per year. ... 

Approximately 80 different carotenoids are synthesized by photosynthetic bacteria. The accumulated carotenoids have certain characteristics ... 

In vivo, one of the main groups of carotenoids are the snlfates of eritoxanthin sulfate and of the caloxanthin sulfates. The sulfates of carotenoids are not associated with pigment-protein complexes, for example, they are neither part of the fight harvesting complexes nor of the reaction centers. In nonphotosynthetic bacteria, carotenoids appear sporadically and when present, they have unique characteristics. Some Staphylococci accumulate C30 carotenoids, flavobacteria C45 and C50, while some mycobacteria accumulate C40 carotenoid glycosides. ... 

Delgado-Vargas, R, Jimenez, A.R., and Paredes-Lopez O., Natural pigments carotenoids, anthocyanins, and betalains — characteristics, biosynthesis, processing, and stability, Crit. Rev. Food Sci. Nutr., 40, 173, 2000. 

Specific carotenoid-protein complexes have been reported in plants and invertebrates (cyanobacteria, crustaceans, silkworms, etc.), while data on the existence of carotenoproteins in vertebrates are more limited. As alternatives for their water solubilization, carotenoids could use small cytosolic carrier vesicles." Carotenoids can also be present in very fine physical dispersions (or crystalline aggregates) in aqueous media of oranges, tomatoes, and carrots. Thus these physicochemical characteristics of carotenoids as well as those of other pigments are important issues for the understanding of their bioavailability. 

In culture, the human colon carcinoma cell hne Caco-2 spontaneously differentiates at confluency into polarized cells with enterocyte-like characteristics. The principle of this approach consists of following the passage of the compound of interest from the apical or lumen-like sides to the basolateral or lymph-hke sides of Caco-2 cells, thus following the absorption of the compound per se. One obhgate step for fat-soluble nutrients such as carotenoids to cross the intestinal barrier is their incorporation into CMs assembled in the enterocytes. Under normal cell culture conditions, Caco-2 cells are unable to form CMs. When supplemented with taurocholate and oleic acid, Caco-2 cells were reported to assemble and secrete CMs. ... 

The characteristic system of conjugated double bonds in the carotenoid molecule in which the Tt electrons are delocahzed over the whole polyene chain is responsible for both absorption of visible light and chemical reactivity, resulting in unstable and easily destroyed compounds. Based on this information, the following precautions must be taken during analysis ... 

It must be underlined that independently of the MS equipment characteristics, no information about stereo-chemistry can be obtained. In fact, cis and trans isomers of the corresponding carotenoid showed identical mass spectra, as did carotenoids with epoxide groups at 5,6 and 5,8 positions. In addition, special care should be taken in assigning carotenoid molecular masses to avoid confusion due to the various ions that may be formed depending on measurement conditions. 

Lockwood SF, Nadolski G, and Foss BJ. 2007. Synthesis of carotenoid analogs or derivatives with improved antioxidant characteristics, Cardax Pharmaceuticals, Hawaii. WO 2007067957. 

NMR spectroscopy is essential for the structure determination of carotenoid isomers because the TI-NMR signals of the olefinic range are characteristic for the arrangement of the isomers. The stereoisomers of astaxanthin, as shown in Figure 4.16, can be separated on a shape-selective C30 capillary column with methanol under isocratic conditions. 

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