Article

Donator Acceptor Map for Carotenoids, Melatonin and Vitamins

Instituto de Investigaciones en Materiales, Universidad Nacional Autonoma de Mexico, Circuito Interior, S N, Ciudad Universitaria, P. O. Box 70-360, Coyoacan, 04510, Mexico.
The Journal of Physical Chemistry A (Impact Factor: 2.78). 09/2008; 112(38):9037-42. DOI: 10.1021/jp803218e
Source: PubMed

ABSTRACT Bright yellow and red colors in animals and plants are assumed to be caused by carotenoids (CAR). In animals, these pigments are deposited in scales, skin and feathers. Together with other naturally occurring and colorless substances such as melatonin and vitamins, they are considered antioxidants due to their free-radical-scavenging properties. However, it would be better to refer to them as "antiradicals", an action that can take place either donating or accepting electrons. In this work we present quantum chemical calculations for several CAR and some colorless antioxidants, such as melatonin and vitamins A, C and E. The antiradical capacity of these substances is determined using vertical ionization energy (I), electron affinity (A), the electrodonating power (omega(-)) and the electroaccepting power (omega(+)). Using fluor and sodium as references, electron acceptance (R(a)) and electron donation (R(d)) indexes are defined. A plot of R(d) vs R(a) provides a donator acceptor map (DAM) useful to classify any substance regarding its electron donating-accepting capability. Using this DAM, a qualitative comparison among all the studied compounds is presented. According to R(d) values, vitamin E is the most effective antiradical in terms of its electron donor capacity, while the most effective antiradical in terms of its electron acceptor capacity, R(a), is astaxanthin, the reddest CAR. These results may be helpful for understanding the role played by naturally occurring pigments, acting as radical scavengers either donating or accepting electrons.

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    • "Countering the trade-off hypothesis for the honesty of carotenoid signalling, Hartley and Kennedy (2004) suggested that carotenoids might not signal directly the carotenoid antioxidant capacity but, instead, signal the quality of other antioxidant resources of the animal. Antioxidants are molecules that scavenge free radicals, thus preventing oxidative stress to damage cells (Surai 2002; Martínez et al. 2008), and these antioxidant molecules include vitamins C, E and A, and antioxidant enzymes (Hartley and Kennedy 2004). Vitamin A has a variety of functions on basic life processes, such as vision, reproduction, growth and development, and also on redox homeostasis and is obtained from animal tissues or derived from β-carotene and other pro-vitamin A carotenoids (Biesalski et al. 2007). "
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    ABSTRACT: Sexual selection promotes the evolution of signals, many of which can reliably indicate condition, health or good genes of individuals. In order to be evolutionarily stable, indicator signals must be costly to produce. Carotenoid colouration evolved in many species by sexual selection. Carotenoids besides acting as pigments have been implicated in immune defence and antioxidation which makes them likely candidates for honest signalling. A trade-off for carotenoid availability was proposed as the basis for signal honesty. Alternatively, it was suggested that carotenoid colouration is not advertising the presence of the pigment per se, but the quality of antioxidant resources which then affect carotenoid concentration. One possibility is that carotenoid-based colouration could signal colourless antioxidant mechanisms, which are partially regulated by vitamins. β-Carotene is one of the most common precursors of vitamin A and, although present in bird diet, is not available for feather colouration. If an indirect association exists between carotenoid signal and condition, then manipulation of β-carotene concentration could reveal that this link is indirect. We tested this by conditioning the availability of β-carotene in the diet of a cardueline finch with yellow carotenoid colouration during moult. β-Carotene-supplemented males had higher plasma carotenoid concentration and higher response to a cellular immunity challenge (phytohaemagglutinin (PHA)) than control males. β-Carotene-supplemented males also had more saturated plumage colouration and were preferred by females in a mate choice test. Our results support the possibility of an indirect role for yellow carotenoid colouration.
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    • "From a chemical perspective, however , the three types of molecules differ in their pro-oxidant potential due to differences in their capacity to accept electrons (see Martínez et al. 2008). Xanthophylls would clearly be the most reactive compounds when cleaved, followed by retinoids, and finally, tocopherol (Martínez et al. 2008). In birds, in fact, two recent experimental studies support a pro-oxidative or toxic action of lutein and zeaxanthin at certain doses (Costantini et al. 2007; Huggins et al. 2010). "
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    ABSTRACT: Carotenoid-based ornaments may have evolved as a consequence of their costs of production, which would assure the reliability of the traits as signals of individual quality. Different costs due to carotenoid allocation to the signal have been proposed, considering the scarcity of these pigments at the environment (ecological cost) and their physiological properties that would trade against the maintenance of the organism. Carotenoids of many red ornaments (ketocarotenoids) are often the result of biotransformation of those pigments abundant in the diet (usually lutein and zeaxanthin). Some authors have suggested that such a conversion implies a cost relevant for signaling because it requires high levels of antioxidant vitamins in the tissues where biotransformation takes place. We explore this hypothesis in red-legged partridges (Alectoris rufa) by analyzing ketocarotenoids in the ornaments (bare parts) and carotenoids, vitamin A in different forms (free and esterified) and vitamin E in blood, liver and fat. Ketocarotenoids in ornaments (astaxanthin and papilioerythrinone) were not found in internal tissues, suggesting that they were directly transformed in the bare parts. However, ketocarotenoid levels where positively correlated with the levels of their precursors (zeaxanthin and lutein, respectively) in internal tissues. Interestingly, ketocarotenoid levels in bare parts negatively and positively correlated with vitamin A and E in the liver, respectively, the same links only being positive in blood. Moreover, retinyl and zeaxanthin levels in liver were negatively related. We hypothesize that storing substrate carotenoids in the main storage site (the liver) implies a cost in terms of regulating the level of vitamin A.
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    • "Carotenoids do not only release electrons they also capture electrons. Electron transfer from radicals to carotenoids has not yet been observed in nature but has recently been predicted (Martinez et al., 2008). Usually, electron transfer to carotenoids is enforced with electrochemical methods, with laser or nuclear radiation (Mairanovsky et al., 1975; Land et al., 1978; Naqvi et al., 2009). "
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