High carotenoid concentration

How Carotenoids Affect Membrane Properties (High Carotenoid Concentration).201... 

HOW CAROTENOIDS AFFECT MEMBRANE PROPERTIES (HIGH CAROTENOID CONCENTRATION)... 

Another factor responsible for regulating the levels of p53 by (3-carotene could be the dose employed. At high carotenoid concentrations, an increase in p53 expression was observed in SCC cells (Schwartz, 1993) and in HL-60 cells (Palozza et al 2002b). In HL-60 cells, the treatment with the carotenoid induced a remarkable increase in ROS production, accompanied by an enhanced expression of p21WAFl and by a concomitant arrest of cell cycle at the G0/G1 phase (Palozza et al., 2002b). An arrest of cell cycle, accompanied by apoptosis induction, was also observed following dietary supplementation with lutein (Chew et al., 2003). The inhibition of mouse mammary tumor growth by lutein was also supported by the observed increase in the expression of p53 and Bax induced by the carotenoid (Chew et al., 2003). 

The carotenoid activity during oxidation is strongly influenced by the oxygen pressure (PO2) of the experimental conditions. Kiokias and Oreopoulou have shown that certain natural carotenoid mixtures (paprika, bixin and tomato, and palm-oil preparations) inhibited the azo-initiated oxidation of sunflower oil-in-water emulsions (operated rapidly under low pOj) in terms of both primary and secondary oxidation products. However, other studies " concluded that carotenoids not only did not inhibit aerial lipid autoxidation (high PO2) but even exerted a prooxidant character, a phenomenon also observed at high carotenoid concentrations that could be due mainly to a more increased formation of carotene-peroxyl radicals, promoting the propagation of autoxidation. 

It has been shown in many studies that protective effects of carotenoids can be observed only at small carotenoid concentrations, whereas at high concentrations carotenoids exert pro-oxidant effects via propagation of free radical damage (Chucair et al., 2007 Lowe et al., 1999 Palozza, 1998, 2001 Young and Lowe, 2001). For example, supplementation of rat retinal photoreceptors with small concentrations of lutein and zeaxanthin reduces apoptosis in photoreceptors, preserves mitochondrial potential, and prevents cytochrome c release from mitochondria subjected to oxidative stress induced by paraquat or hydrogen peroxide (Chucair et al., 2007). However, this protective effect has been observed only at low concentrations of xanthophylls, of 0.14 and 0.17 pM for lutein and zeaxanthin, respectively. Higher concentrations of carotenoids have led to deleterious effects (Chucair et al., 2007). 

Table IV. Differential inhibition of sterol accumulation and of the light-induced prenyllipid accumulation at high mevinolin concentration in excised 9-day-old etiolated primary wheat leaves during 18 h of continuous white light. Prenyllipids in U8 per 40 leaf segments. Mean of 2 runs with SD < 10%. X = Xanthopylls c = S-carotene x-i-c = sum of carotenoids. Chlorophylls and carotenoids were separated by TLC (1) and determined photometrically.

The concentrations of carotenoids and the level of oxygen they are exposed to can also influence their antioxidant activities. At low oxygen partial pressures, diverse carotenoids effectively inhibit in vitro oxidation reactions, and their antioxidative abilities increase with increasing carotenoid concentration." " As oxygen levels are increased, however, their antioxidant potential typically decreases." " Certain carotenoids, notably P-carotene but also lycopene, exhibit unusual behavior beyond a threshold carotenoid concentration, they actually decrease in antioxidant ability with increasing carotenoid concentration, and this effect is further exacerbated at high oxygen levels." This prooxidant... 

The stability of carotenoids in fish flesh during all phases of processing from harvest to consumption is critical to ensure optimal acceptance of aquaculture fish products (Chen et al, 1984a). Ostrander et al, (1976) reported on the importance of proper coloration of salmon flesh to consumers. Visual color scores become less sensitive at high tissue carotenoid concentrations (Foss et al, 1987) and there is a need to achieve the pigment level necessary for consumer satisfaction without incurring the expense of excess carotenoid feeding. 

The yellow coloration of egg yolks is important for consumer acceptance of this product. Moderately colored egg yolks are appropriate for table use, while highly colored yolks are desired as ingredients in processed foods (Klaui and Bauernfiend, 1981). The pigmentation of yolk is directly correlated to the amount and type of carotenoid supplementation (Marus-ich et al, 1960). The addition of antioxidants to carotenoid-supplemented diets resulted in increased pigmentation of egg yolks over those without added antioxidant (Madiedo and Sunde, 1964). It is likely that the antioxidant provided a protective effect for the carotenoid during feed storage and/or in the digestive tract of the bird. Williams etal. (1963) reported that 8-10 days are required to reach a steady-state carotenoid concentration in egg yolks of hens provided a carotenoid-rich diet. 

---