Carotenoids xanthophylls

Chemical properties of carotenoids play an important role in carotenoid micellarization and, therefore, bioavailability. Apolar carotenoids (carotenes) are generally incorporated in the central region, which is highly hydrophobic, of the oil droplets, whereas polar carotenoids (xanthophylls) are localized on the surface, and therefore xanthophylls are more easily micellarized and absorbed than carotenes (Borel and others 1996). van het Hof and others (2000) found in humans that lutein is five times more bioavailable than (3-carotene. 

The carotenes and carotenoids are very important accessory pigments (Fig. 23-22). The major component in most green plants is (3-carotene. Green sulfur bacteria contain y-carotene in which one end of the molecule has not undergone cyclization and resembles lycopene (Fig. 22-5). Chloroplasts also contain a large variety of oxygenated carotenoids (xanthophylls). Of these, neoxanthin, violaxanthin... 

There are an abundance of colorful and multifunctional phy to chemicals or nutraceuticals such as carotenoids, xanthophylls, flavonoids, and anthocyanins in nature. These colorful phytochemicals are present in our daily intake of fruits and vegetables, and sometimes from shrimp and sea fish. Additionally, the colorful phytochemicals are also distributed in processed foods such as juices, jams, teas, wines, infusions and decoctions, extracts, and other... 

FIGURE 3.10 Examples of oxygenated carotenoids (xanthophylls) (a) zeaxanthin (P,P-car-otene-3,3 -diol) (b) eschscholtzxanthin (4, 5 -didehydro-4,5 -refro-P,P-carotene-3,3 -diol) (c) 5,6-seco-P-carotene-5,6-dione and (d) 3 -hydroxy-8-apo-P-carotene-8-al. 

Isopentenyl pyrophosphate Hemiterpenes (isoprene). Monoterpenes (iridoid components of volatile oils). Sesquiterpenes (bitter principles, components of volatile oils). Diterpenes (components of resins, gibberellins, phytol). THterpenes (squalene, sterols, etc.). Tetraterpenes (carotenoids, xanthophylls). Polyterpenes (caoutchouc, gutta percha). 

Kirchner (1978) has discussed the utility of thin-layer chromatography for the following natural pigments chlorophylls, carotenoids, xanthophylls, flavonoids, anthocyanins, porphyrins, and bile. From the standpoint of practical TLC, the most important of these pigments are the chlorophylls, carotenoids, xanthophylls, and anthocyanins, and it is these pigments that are considered further in this chapter. For practical TLC of the flavonoids, consult Harbome (1984, 1992). For information on the TLC of porphyrins, see Doss (1972), Dolphin (1983), and Jacob (1992). Jain (1996) has provided useful information on the examination of porphyrins (in studies on clinical porphyrias) by TLC in clinical chemistry. 

Food additive/ supplement Carotenoids (xanthophylls, carotenes) Colourants, antioxidants, provitamin A (carotenes)... 

Table 1. Redetermined specific absorption coefficients (SAC) for chlorophyll a and b at the peak maxima of each (underlined) and at 47Qnm plus the eJIui values at 470 nm for total leaf carotenoids (xanthophylls = x plus carotenes = c) in different solvents.

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