Carotenoid-protein complexes

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. 

The hydrolysis of zeaxanthin esters by a carboxyl ester lipase indeed enhanced both the incorporation of zeaxanthin in the micellar phase and uptake of zeaxanthin by Caco-2 cells. As mentioned earher, carotenoids can also be linked to proteins by specific bindings in nature and these carotenoid-protein complexes may slow the digestion process and thus make their assimilation by the human body more difficult than the assimilation of free carotenoids. Anthocyanins are usually found in a glycosylated form that can be acetylated and the linked sugars are mostly glucose, galactose, rhamnose, and arabinose. 

A more difficult problem to overcome is the overestimation of carotenoid concentrations in processed foods due to the usually more efficient extraction of carotenoids in such foods as a result of the denaturation of the carotenoid-protein complexes and cell damage. In addition, weight changes due to loss or gain of water or fat, enzymatic oxidation of carotenoids in raw samples, and leaching of soluble solids during processing should be considered. 

Lobster and shrimp dine on carotenoid-containing plankton, and the compounds become concentrated in their shells. Here the carotenoids are bound up with protein molecules, and the carotenoid-protein complex has a dark green color. When the protein is heated, it is denatured. In other words, it breaks down and disassociates from the reddish pigment, astaxanthin, which then becomes visible. To a smaller extent this is also evident in cooked carrots, which become more orange than they were before. This was another experiment my daughter and I decided to try. We cooked up some fresh carrots to see if they would become more orange. They did, but the effect was not as pronounced as it was with the shrimp, because carrots have little protein. 

Common unit operations of food processing are reported to have only minor effects on the carotenoids (Borenstein and Bunnell 1967). The carotenoid-protein complexes are generally more stable than the free carotenoids. Because carotenoids are highly unsaturated, oxygen and light are major factors in their breakdown. Blanching destroys enzymes that cause carotenoid destruction. Carotenoids in frozen or heat-sterilized foods are quite stable. The stability of carotenoids in dehydrated foods is poor, unless the food is packaged in inert gas. A notable exception is dried apricots, which keep their color well. Dehydrated carrots fade rapidly. 

Babu, C. M., Chakrabarti, R., and Sambasivarao, K. R. S. (2008). Enzymatic isolation of carotenoid-protein complex from shrimp head waste and its use as a source of carotenoids. LWT 41, 227-235. 

Carotenoid-Protein Complexes. Three new purple-blue carotenoprotein complexes from invertebrate animals have been described. That from the carapace of Orconectes limosus (Amax 335, 460, 675 nm) has astaxanthin (8) and canthaxanthin [p,p-carotene-4,4 -dione (10)] as prosthetic group,30 and that from the fly Rhyn-chosciara americana (Amax 465, 545 nm) has one canthaxanthin and one echinenone [P,P-caroten-4-one (11)] per mole of protein.31 The sponge Suberites domuncula... 

Other Degraded Carotenoids Carotenoid-Protein Complexes Physical Methods Separation and Assay N.M.R. Spectroscopy Electronic Absorption Spectroscopy Resonance Raman Spectroscopy X-Ray Structures Linear Dichroism... 

Carotenoid-Protein Complexes. The partial characterization of an astaxanthin- or zeaxanthin-containing carotenoprotein (mol. wt. >30000) from hydrocorals has been reported. Other papers present a spectroscopic characterization of the lobster pigment a-crustacyanin and report effects of changes in pH and ionic strength on its spectroscopic properties. ... 

New Natural Products Related to Carotenoids Carotenoid-Protein Complexes Synthesis and Reactions Carotenoids Retinoids... 

As can be concluded from the above outline, access to carotenoids isotopically labelled with and at predetermined positions is an essential part of this strategy. Labelled carotenoids can be prepared in two ways, namely by biosynthesis or by chemical synthesis. For the preparation of specifically labelled carotenoids biosynthesis is not suitable the labelled carotenoids are obtained by growing bacteria or yeasts on media containing simple isotopically labelled precursors such as sodium acetate [19]. The position of labelling can often not be predetermined and multiple labelling often occurs. Another major disadvantage is that isotopic dilution occurs for studies of carotenoid-protein complexes, carotenoids labelled at specific positions with high isotopic enrichment (preferably >99%) are needed. 

Zagalsky, P. F. Carotenoid-protein complexes. Pure and Applied Chem. 47, 103 (1976). 

The yellow-to-red color of most carotenoids is caused by the conjugated trans-double bonds. Carotenoid-protein complexes (caroteno-proteins) may be yellow, red, or blue. 

An interesting question relates to the localization of carotenoids within fish flesh. Depot fats of salmon do not appear to be pigmented to the degree shown in flesh. D Abramo et aL (1983) have reported that astaxanthin is found in carotenoid-protein complexes, termed carotenoproteins, in crustacean tissue. The nature of the carotenoid-protein bond appears ionic in nature. Henmi et aL (1987) presented evidence that carotenoids bind in a hydrophobic manner to the actomyosin complex of muscle tissue. 

Organisms Presence of carotenoids in species Characteristic carotenoids Carotenoid derivatives Carotenoid- protein complexes... 

Astaxanthin is present in crab and lobster shells and lobsters, the red astaxanthin is released from and, in combination with proteins, provides three a green carotenoid-protein complex. Astaxanthin blue hues (a-, 3- and y-crustacyanin) and one usually occurs in lobster shell as an ester, e. g., diyellow pigment. During the cooking of crabs palmitic ester. 

Zagalsky, P.F. (1983) Carotenoid-protein complexes in marine organisms. Oceanis, 9, 73-90. 

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