Sources of carotenoids

The total production of carotenoids in nature has been estimated at 10 tonnes/ 

In plants, carotenoids are held in the chloroplasts, where they are found as complexes formed through non-covalent binding with proteins. Within the chloroplasts, carotenoids have important functional roles as accessory lightharvesting pigments and as photo-protective agents. 

Lutein is the dihydroxy form of a-carotene, and is distributed among a variety of vegetables. Zeaxanthin is the dihydroxy form of P-carotene, and is present in com (maize) and various vegetables. The highest amounts of lutein and zeaxanthin are found in egg yolk and in com (Sommerburg et al, 1998). 

Lutein is also the major carotenoid in kiwi fruit, red seedless grapes, zucchini squash and pumpkin, while zeaxanthin is the major carotenoid in orange pepper. 3-Cryptoxanthin is also distributed in foodstuffs such as broccoli and green grapes, and is one of the major carotenoids detectable in human blood. 

Recently, Homero-M6ndez and Mmguez-Mosquera (2000) highlighted an alternative carotenoid source in Rosa mosqueta hips. Six major carotenoids were identified. The average composition was estimated as 497.6 mg/kg P-carotene, 391.9 mg/kg lycopene, 703.7 mg/kg rubixanthin, 289.2 mg/kg gazaniaxanthin, 183.5 mg/kg P-cryptoxanthin, 266.6 mg/kg zeaxanthin, and 67.1 mg/kg minor carotenoids (dry-weight basis). 

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Fertile sources of carotenoids include carrots and leafy green vegetables such as spinach. Tomatoes contain significant amounts of the red carotenoid, lycopene. Although lycopene has no vitamin A activity, it is a particularly efficient antioxidant (see Antioxidants). Oxidation of carotenoids to biologically inactive xanthophyUs represents an important degradation pathway for these compounds (56). 

Table 7.1 Common dietary sources of carotenoids in regular vegetable foods, xg/100 fresh weight. Data are means derived from literature sources. The normal range of values is the mean at least 85%, and depends upon variety, agronomic conditions, tissue sampled and maturity... 

Table 7.1 shows the common dietary sources of carotenoids in regular vegetable foods, p,g/100 fresh weight. Although the greatest amount of the hydrocarbon carotenoids is present as the all-trans isomer, there is always a proportion of cis isomers present. This table represents only a small number of the fruits and vegetables that contribute carotenoids in the European diet. For more comprehensive information readers are directed to A European Carotenoid Database O Neill et al, 2001, which lists the carotenoid composition of over 100 food items. 

Daily consumption of various fruits, vegetables, and derived juices contributes to human intake of carotenoids. The estimation of carotenoid intakes has been made possible throngh publication of the qnalitative and qnantitative carotenoid contents of commonly consnmed foods. Average intake estimates in the United States are around 6.5 mg/day. In seven conntries in Enrope, the average total carotenoid intake based on the snm of the five carotenoids was approximately 14 mg/day. When dietary source of carotenoids were analyzed, carrots appeared as the major sonrces of p-carotene in all conntries except Spain, where spinach was the main contribntor. 

Vegetables are the most important source of carotenoids for humans. Most vegetables contain a variety of carotenoids [30,31]. Only carrots O-carotene) and tomatoes (lycopene) [32] contain one major carotenoid. However, even in these vegetables, several minor components can be identified, most of them geometrical isomers - structurally similar, but nevertheless totally different. For nutritional aspects, the level of these stereoisomers in nature is significant, because their biomedical properties can differ enormously. 

Table 10.1 Relative distribution and source of carotenoids in multicarotenoid mixture (MCM).

The characteristic deep-red color of ripe tomato fruit and related products is mainly due to lycopene. This color serves as an important indicator of their quality. Tomatoes and tomato foods are an important source of carotenoids for humans and are a major source of lycopene in the Western diet. Other important sources of dietary lycopene include watermelon, guava, rose hip, papaya and pink grapefruit (Gross, 1987,1991 Beerh and Siddappa, 1959 Mangels et al., 1993) (Table 4.3). 

Babu, C. M., Chakrabarti, R., and Sambasivarao, K. R. S. (2008). Enzymatic isolation of carotenoid-protein complex from shrimp head waste and its use as a source of carotenoids. LWT 41, 227-235. 

Nelis, H.J. and De Leenheer, A.P. 1991. Microbial sources of carotenoid pigments used in foods and feeds. J. Appl. Bacteriol. 70, 181-191. 

Theaspiranes and Vitispiranes. The shrub Osmanthus fragrans is a member of the oleaceae family which grows in eastern Asia. It is a rich source of carotenoid degradation products, many of which have also been found in other plant sources. Some of these are shown in Figure 8.26 and it is evident in the figure how they are related to each other and to the ionones. 

IPP, a Cs-compound, is the source of carotenoids, isoprenoids, terpenes, quinones, and phytol of BChls and Chls. There are two known independent pathways of IPP synthesis the classical mevalonate (MVA) pathway and the alternative, non-mevalonate, l-deoxy-D-xylulose-5-phosphate (DOXP) pathway [19, 20]. In the MVA pathway, acetyl-coenzyme A is converted to IPP through mevalonate. The enzymes and genes involved in this pathway are well studied [21]. The DOXP pathway was found in the 1990s, and in this pathway, pyruvate and glyceraldehyde are converted to IPP. 

On the basis of structure alone, Simpson and Chichester (1981) estimate that 50-60 carotenoids and apocarotenoid compounds could have provitamin A activity. Only a few of the identified carotenoids, however, have both vitamin A activity and occur in significant amounts in natural foods as commonly eaten by vertebrate animals (Bauemfeind, 1972). Of these, p-carotene has by far the most provitamin A activity. The a- and y-carotenoids and cryptoxanthin (3-hy-droxy-P-carotene), also found in substantial amounts in commonly consumed foods, have about one-half the activity of the P form. Table I contains a list of the provitamin A activity found in the most important mammalian food sources of carotenoids. Table II lists vitamin A-inactive carotenoids commonly found in food. 

Red palm oil is also a convenient and rich source of natural carotenoids (Choo, 1996). It is obtained from the fruits of the palm tree, Elaeis guineensis, of which a large number of subspecies are known. Palm oil extracted from a commercially planted species E. guineensis var. Tenera) in Malaysia was reported to have a carotenoid content of about 500-700 ppm (Goh et al., 1985). Choo (1994) reported that palm oil is the richest natural plant source of carotenoids, with a-carotene and P-carotene being the major ones present. Tables 3 and 4 show the carotenoid contents of different oil palm species and palm oil fractions. 

Ong, ASH and Tee, ES (1992) Natural sources of carotenoids from plants and oils. Methods Enzymol, 213,142-167. 

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