Antioxidant properties of carotenoids

The food technologist may be especially interested in the fate of the carotenoids in the seed oil. Like red palm oil, the resulting carotenoid-pigmented canola oil may be more stable due to the antioxidant properties of carotenoids and may be more attractive to consumers. Alternatively, for food security concerns, transgenic soybean or canola oils and seed meals that are genetically modified for more efficient bio-diesel production may be bio-safety marked with lipid-soluble carotenoids and water-soluble anthocyanins, respectively. Potatoes are excellent potential sources of dietary carotenoids, and over-expression of CrtB in tubers led to the accumulation of P-carotene. Potatoes normally have low levels of leaf-type carotenoids, like canola cotyledons. 

As the therapy of AMD is very limited, there is an urgent need to develop an intervention to prevent vision loss. The epidemiological data together with the well-documented antioxidant properties of carotenoids in studies in vitro and with proven increases in macular pigment density in most people via dietary supplementation (Beatty et al., 2004 Berendschot et al., 2000 Bone et al., 2003 Hammond et al., 1997 Iannaccone et al., 2007 Landrum et al., 1997), including patients with early AMD (Koh et al., 2004 Obana et al., 2008 Richer et al., 2007 Trieschmann... 

Stahl, W., Ale-Agha, N., and Pohdori, M.C. 2002. Non-antioxidant properties of carotenoids. Biol Chem 383 553-558. 

These results suggest that the potential pro-oxidant effects of carotenoids should always be considered when carotenoids are proposed for use as colourants in lipid-containing foods. Carotenoids have special and remarkable properties, and their functions and actions vary significantly in different systems. Britton (1995) considered it essential that studies of the antioxidant properties of carotenoids be based on chemical principles and on the relationships between structure, properties and function. 

Carotenoids play a key role in human diet by virtue of their metabolism to vitamin A (retinol, 61). As the prosthetic group associated with the light-harvesting pigment rhodopsin, retinol is critically involved in visual processes. It is also a participant in growth and development processes, so vitamin A deficiency, which is estimated to inflict 124 million children worldwide, can have serious consequences for long-term health (Beyer et al. 2002). The antioxidant properties of carotenoids have also been implicated in the protection against heart disease and cancer (Fraser and Bramley 2004). 

As has already been stated, the carotenoids are lipophilic and are therefore absorbed and transported in association with the lipoprotein particles. In theory, this fortuitous juxtaposition of lipid and carotenoid should confer protection on the lipid through the antioxidant properties of the carotenoid. No doubt some antioxidant protection is afforded by the presence of the carotenoids derived from the diet. However, with one or two exceptions, human supplementation studies have not supported a role for higher dose carotenoid supplements in reducing the susceptibility of the low-density lipoproteins to oxidation, either ex vivo or in vivo (Wright et al, 2002 Hininger et al, 2001 Iwamoto et al, 2000). 

Young, A.J. and Lowe, G.M., Antioxidant and prooxidant properties of carotenoids. Arch. Biochem. Biophys., 385, 20, 2001. 

Many reviews have been written about the antioxidant activities of carotenoids. Some also describe prooxidant activities. - In consequence, only selected points about this very broad subject will be presented in the first part of this chapter. Linked to these properties and important for food nutritional value is the stability of caro-... 

This method is also used to measure ex vivo low-density lipoprotein (LDL) oxidation. LDL is isolated fresh from blood samples, oxidation is initiated by Cu(II) or AAPH, and peroxidation of the lipid components is followed at 234 nm for conjugated dienes (Prior and others 2005). In this specific case the procedure can be used to assess the interaction of certain antioxidant compounds, such as vitamin E, carotenoids, and retinyl stearate, exerting a protective effect on LDL (Esterbauer and others 1989). Hence, Viana and others (1996) studied the in vitro antioxidative effects of an extract rich in flavonoids. Similarly, Pearson and others (1999) assessed the ability of compounds in apple juices and extracts from fresh apple to protect LDL. Wang and Goodman (1999) examined the antioxidant properties of 26 common dietary phenolic agents in an ex vivo LDL oxidation model. Salleh and others (2002) screened 12 edible plant extracts rich in polyphenols for their potential to inhibit oxidation of LDL in vitro. Gongalves and others (2004) observed that phenolic extracts from cherry inhibited LDL oxidation in vitro in a dose-dependent manner. Yildirin and others (2007) demonstrated that grapes inhibited oxidation of human LDL at a level comparable to wine. Coinu and others (2007) studied the antioxidant properties of extracts obtained from artichoke leaves and outer bracts measured on human oxidized LDL. Milde and others (2007) showed that many phenolics, as well as carotenoids, enhance resistance to LDL oxidation. 

Lako J, Trenerry, VC, Wahlqvist M, Wattanapenpaiboon N, Sotheeswaran S and Premier R. 2007. Phytochemical flavonols, carotenoids and the antioxidant properties of a wide selection of Fijian fruit, vegetables and other readily available foods. Food Chem 101(4) 1727-1741. 

Abstract Low molecular weight antioxidants are an important part of the antioxidative defense mechanisms of cells and organisms. This chapter gives a short overview of the actions of the main antioxidants, including uric acid, ubichinones,lipoic acid, vitamins C and E, carotenoids, and phenolic compounds. The antioxidative properties of these endogeous and nutritional compounds are discussed in this chapter. However, it is critically discussed whether the antioxidative properties of some of these compounds are really important in vivo. 

Antioxidant and prooxidant properties of carotenoids have recently been reviewed [50,51]. Carotenoids serve as efficient quenchers of single oxygen. Their assumed function as antioxidants in vivo is largely based on model experiments. 

Beutner, S., Bloedom, B., Frixel, S., Blanco, L, Hoffmann, T., Martin, H., Mayer, B., Noack, P, Ruck, C., Schmidt, M., Schulke, L, Sell, S., Ernst, H., Haremza, S., Seybold, G., Sies, H., Stahl, W., and Walsh, R. 2001. Quantitative assessment of antioxidant properties of natural colorants and phytochemicals carotenoids, flavonoids, phenols and indigoids. The role of P- carotene in antioxidants functions, J. Sci. Food Agric., 81, 559. 

The position, concentration, and orientation of carotenoids within membranes may strongly influence both the structure and dynamics of the lipid bilayer and the antioxidant properties of the carotenoids in membrane systems." Polar carotenoids such as zeaxanthin and astaxanthin may span the bilayer, where they tend to stabilize and rigidify the hpid membrane, while nonpolar carotenoids such as P-carotene are more likely to remain completely within the bilayer. In the case of astaxanthin, intermolecular hydrogen bonds likely form with phospholipids in the membrane, anchoring the carotenoid molecule like a rivet. At the same time, intramolecular hydrogen bonding between the keto and hydroxyl groups of individual astaxanthin molecules can increase... 

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