Carotenoid excess

It is well known that excessive intake of P-carotene may lead to carotenodermia (yellow skin), and it is undoubtedly the case that some carotenoid is directly lost via the skin or through photo-oxidation in the skin. As far as is known the carotenoids are not cytotoxic or genotoxic even at concentrations up to 10 times the normal plasma concentration which may cause carotenodermia. However, they are associated with amenorrhoea in girls who may be consuming bizarre diets and, in long-term supplementation studies, with an increase in lung cancer (The Alpha-tocopherol, Beta-carotene Cancer Prevention Study Group, 1994). 

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. ... 

The overall process of ()2 quenching simply converts the excess energy of singlet oxygen to heat via the carotenoid [CAR] lowest excited triplet state [3CAR],... 

Finally, radical cations can be generated in solution by different types of pulse radiolysis225. Like PET, this is inherently a method for transient spectroscopic observations, but it has proved to be invaluable in investigations of dimer cations, e.g of polyenes, which form spontaneously upon diffusion of radical cations in the presence of an excess of the neutral parent compound, but a discussion of the electronic structure of such species is beyond the scope of this review. Pulse radiolysis is of interest in the present context because it allows the observation of large carotenoid radical cations which are difficult to create in solid-state or gas-phase experiments... 

Although the benefits of many functional ingredients have yet to be proven, there is a possibility for new health problems to arise if the market for fortified functional foods continues to expand. Some consumers may ingest excessive amounts of certain nutritional food additives such as iron, which could lead to an increased incidence of hemachromatosis in genetically predisposed people. Fortification with specific carotenoids may competitively inhibit the bioavailability of other carotenoids, perhaps leading to adverse physiological consequences. 

Havaux, M. and Kloppstech, K., The protective functions of carotenoid and flavonoids pigments against excess visible radiation at chilling temperature investigated in Arabidopsis npq and tt mutants, Planta, 213, 953, 2001. 

Following extraction, an efficient way of initiating the isolation of carotenoids is to saponify the extract. This removes many of the unwanted lipids present in the sample as well as chlorophyll. The saponification by-products, which to a great extent are sodium or potassium salts, are easily separated by an aqueous solution of a highly polar salt. The addition of water also helps wash off excess alkali and other water-soluble and water-complexed compounds. This procedure hydrolyzes xantho-phyll esters to form the hydroxylated carotenoid. 

Complete dehydration before extraction is not recommended. A small amount of water is often useful when a low-polarity solvent mixture is the extractant. On the other hand, excess water may make extraction inefficient. Using the right extractant is of great importance and depends largely on which carotenoids are sought. Using the hexane/acetone mixture as the extractant is advantageous because the same pair of solvents is used later for crystallization. 

Food samples are dissolved in water and acidified with acetic acid (135,157). According to Gilhooley et al. (157), excess methanol has to be removed from solutions before passing through polyamide because it impairs the adsorption of the dyes by the polyamide. The solution is stirred with polyamide powder, and the slurry is transferred to a microcolumn or it is passed through the column of polyamide. The latter is recommended since dyes are adsorbed as a narrow band at the top of the column. The column is washed with hot water to remove sugars, acids, and flavoring materials and with acetone to remove basic dyes, water-soluble carotenoids, and some antho-cyanins. The adsorbed acid dyes are eluted with methanol sodium hydroxide (164,172,175), with methanol ammonia (176), or with acetone ammonia (157). Acetone ammonia is preferred because it can be removed in a water bath and, on addition of acid, no salts are formed that interfere with the adsorption of the dyes by the polyamide (157). The eluate is evaporated to dryness and redissolved in the HPLC mobile phase (156). 

This behaviour suggests that carotenoids not only remove the toxic singlet oxygen but can also neutralize the energy excess that is transferred from chlorophyll to molecular oxygen [1,125],... 

Many bioactive phytochemicals were systematically studied after their fractionation and characterization from many vegetables and fruits. New biological effects such as the differentiation-inducing activity of carotenoids— particularly vitamin A—were described in the 1930s. In addition, several experimental results suggested that various carotenoids might serve as dietary chemopreventive agents [6] because of their ability to quench excited molecules and excess radicals. 

Crocetin (C20) is a yellow (IP)2—(PI)2-derived dicarboxylic, acid (generalized structure -OOG-Gig-GOO-) from the styles of Crocus sativus (Iridaceae) (the saffron of Indian cooking and Buddhist robes). Grocin, the digentiobiose ester of crocetin, is water soluble, unlike other carotenoids which are lipophilic (fat soluble). Crocetin is a protein kinase inhibitor. Excess vitamin A (or excess pro-vitamin A) ingestion is toxic (dog liver consumption having caused the death of Sir Douglas Mawson s explorer companions in the Antarctic by this mechanism). 

Preformed vitamin A is found only in animals and a small number of bacteria. A number of the carotenoid pigments in plants can be cleaved oxidatively to yield retinol /S-carotene is quantitatively the most important of these provitamin A carotenoids. Although preformed retinol is both acutely and chronically toxic in excess, carotene is not, because there is only a limited capacity to cleave it to retinol. 

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