Carotenoid pigments, molecular

ARMSTRONG G A and HEARS j E (1996) Genetics and molecular biology of carotenoid pigment biosynthesis , 7,10, 228-37. 

Polar carotenoids present in membranes have been shown to limit molecular oxygen penetration into lipid bilayer as demonstrated by the pigment-related decrease of the oxygen diffusion-concentration product (Subczynski et al., 1991). This effect, being most probably a direct consequence of the influence ofthe carotenoids on molecular dynamics and structure of lipid membranes, appears particularly important taking into consideration the deleterious role of active oxygen species with respect to biomembranes. 

A close relationship exists between physicochemical properties of pigment molecules and their ability to be absorbed and thus to exhibit biological functions. Carotenoids are hydrophobic molecules that require a lipophilic environment. In vivo, they are found in precise locations and orientations within biological membranes. For example, the dihydroxycarotenoids such as lutein and zeaxanthin orient themselves perpendicularly to the membrane surface as molecular rivets in order to expose their hydroxyl groups to a more polar environment. 

The bioaccessibility of a compound can be defined as the result of complex processes occurring in the lumen of the gut to transfer the compound from a non-digested form into a potentially absorbable form. For carotenoids, these different processes include the disruption of the food matrix, the disruption of molecular linkage, the uptake in lipid droplets, and finally the formation and uptake in micelles. Thus, the bioaccessibility of carotenoids and other lipophilic pigments from foods can be characterized by the efficiency of their incorporation into the micellar fraction in the gut. The fate of a compound from its presence in food to its absorbable form is affected by many factors that must be known in order to understand and predict the efficiency of a compound s bioaccessibility and bioavailability from a certain meal. ... 

Among all food pigments, we have the most knowledge about the carotenoids related to their absorption and metabolism on a molecular basis. 

Carotenoids are one of the most abundant groups of pigments found in nature. Every year more than 100 million tonnes of them are being synthesized in the biosphere. Nearly 600 molecular species of carotenoids are currently identified (Del Campo et al., 2007). As powerful antioxidants, vitamin precursors, natural colorants, and odorants they became a serious global market commodity accounting for almost 1 billion dollars of the yearly trade (BCC research, 2007). 

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