Lipophilic pigments carotenoids

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. ... 

CO2 extraction has been prevalent for the isolation of essential oils and other natural lipophilic pigments like carotenoids. Hot water and superheated water extraction methods are used for analytical preparation of polar pigments. The technique is commonly referred to as subcritical water extraction because the practitioners of this approach come from SEE backgrounds. 

Because most food matrices are water soluble, many efforts were directed to the formulation of lipophilic pigments (mainly carotenoids) into water-soluble formulations (powders or gels). For hydrophilic pigments like flavonoids, polar dried microcapsules are the most popular ways to stabilize their functionality. Extracts rich in P-carotene were encapsulated using three different encapsulation techniques (spray drying, drum drying, and freeze drying)." ... 

It makes possible a selective concentration of lipophiles in the membranes. Vesicles made of n-acyl lipids or of polyprenyl phosphates extract selectively into the membrane any lipophilic substance lipophilic pigments (Nile Red), cholesterol, polyprenols, carotenoids, etc. This is particularly important for those lipophilic substances that play a role in stabilizing the membrane cholesterol, hopanoids, polyprenols, and carotenoids (Bisseret et al., 1983 Milon et al., 1986 Lazrak et uZ.,1988 Krajewski-Bertrand et al., 1990). 

Carotenoids are widespread yellow and orange (rarely yellow-green and red) lipophilic pigments of plants, fungi, algae, microorganisms and some animals (crustaceans, fish, birds and mammals). Their annual production in nature is estimated at 1x10 tons. In plants,... 

The purpose of this chapter is to provide an overview of our present knowledge about the health benehts of pigments, particularly their effects on chronic diseases. We examine the effects of lipophilic (carotenoids, chlorophylls) and hydrophilic pigments (anthocyanins and flavones-flavonols), and curcumin. Descriptive and mechanistic studies are reviewed in regard to common chronic diseases. 

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 industrially produced carotenoids are obtained in high overall yield and excellent quality by the processes described in Sections B and C [91]. The crystalline products have an (all-i j-content > 96%. The total amount of (Z)-isomers and minor pigments is below 4 %. Polar triphenylphosphine oxide (56) may be separated virtually quantitatively from the desired lipophilic products. The amounts of residual solvent are at most 0.1 %. Such a high level of purity could only be achieved for such carotenoids from natural sources by a very costly isolation procedure. 

Carotenoids are commonly extracted from liquid samples (plasma/serum) into lipophilic solvents such as hexane, hexane-ethyl acetate, or diethyl ether, mostly after deproteinization with ethanol or methanol, which also helps to liberate the lipidic substances from protein binding. Extracts should be protected from light and acids and antioxidants may usefully be added. The extract is either used as such or is concentrated under oxygen-free nitrogen. Solid samples, e.g., foods, are either extracted with a solvent miscible with water (acetone, methanol) or, after dehydration of the sample, with a water immiscible solvent. Cleanup of the extract and fractionation of the pigments may involve saponification and/or open-column chromatography. 

Reversed-phase separation of carotenoids on octadecyl-bonded silica provides a mild and sensitive method for the TLC analysis of chloroplast pigments. The separation can be explained on the basis of partition between the mobile phase and the hydrophobic surface of the modified silica gel layer, but the separation mechanism is not fully understood. Less polar compounds such as the carotenes are strongly held according to their lipophilic nature. The retention of the xanthophylls is determined mainly by the nature and the number of the oxygenated substituents. Representative Ry values as found for some carotenoids with this system are shown in Table 7. Solvent systems 2 and 3 are most suitable for general separations, while system I gives a better separation of the more polar compounds. 

Terpenes are generally lipophilic compoimds based on a simple five-carbon building block (isoprene unit). Monoterpenes are composed of two isoprene units (CIO), sesquiterpenes possess three isoprene units (Cl5), whereas diterpenes have four (C20), etc. Some terpenes, mainly isoprenes, mono- and sesquiterpenes are volatile and are referred to as volatile organic compounds (VOC). The terpene family includes hormones, carotenoid pigments, latex and most essential oils [HOP 03]. Terpenes play different roles such as attracting pollinators and protecting against herbivores, toxic insecticides and insect repellents [HOP 03]. 

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