Carotenoids leafy vegetables

Mercadante, A.Z. and Rodriguez-Amaya, D.B., Carotenoid composition and vitamin A value of some native Brazilian green leafy vegetables, Int. J. Food Sci. Technol, 25, 213, 1990. 

Although saponification was found to be unnecessary for the separation and quantification of carotenoids from leafy vegetables by high performance liquid chromatography (HPLC) or open column chromatography (OCC), saponification is usually employed to clean the extract when subsequent purification steps are required such as for nuclear magnetic resonance (NMR) spectroscopy and production of standards from natural sources. 

Mercadante A Z and Rodriguez-Amaya D B (1991), Carotenoid composition of a leafy vegetable in relation to some agricultural variables , J Agric Food Chem, 39, 1094— 1097. 

As in the case of polyphenols, some of the carotenoids contained in fruits and vegetables are bound to the DF matrix. For instance, between 20% and 70% of the (3-carotene and lutein in green leafy vegetables was found to be associated with the DF matrix. The bulk of the unreleased carotenoids was associated with the IDF, and a very small proportion was associated with the SDF (Serrano and others 2005 Goni and others 2006). 

Lutein [E161 (b)J. Lutein is one of the four most common carotenoids found in nature. The EU classifies it as E161(b). Chemically, lutein is a xanthophyll and is similar to P-carotene. Although lutein occurs in all green leafy vegetation, egg yolks and in some flowers the commercial sources are the petals of the Aztec marigold and, to a lesser extent, alfalfa. 

Another liquid chromatographic method has been developed for obtaining standards and RP-HPLC quantification of leafy vegetable carotenoids. Carotenoids were extracted... 

COMPARISON OF CAROTENOID COMPOSITION (juG/G) OF LEAFY VEGETABLES OBTAINED BY ONE-POINT CALIBRATION, STRAIGHT LINE EQUATION AND RESPONSE FACTORS... 

Vegetables are the major sources of provitamin A carotenoids, followed by fruits. Milk products, egg yolk, shellfish, and Crustacea also contain active carotenoids, which are derived from the animal s diet. The carotenoid distribution in green leafy vegetables is generally constant, whereas fruits contain a greater variety of carotenoids in varying concentrations. In ripening fruits, the decrease in chlorophylls is frequently accompanied by an increase in the concentration of carotenoids and an increase in the ratio of carotenes to xanthophylls. 

The methodology depends on the known carotenoid distribution in plant tissues, which can be classified into three main groups (1) those in which the vitamin A value is due almost exclusively to /3-carotene (e.g., green leafy vegetables, peas, broccoli, sweet potatoes, tomatoes, watermelon, mango) (2) those in which primarily a- and /3-carotene account for the vitamin A value (e.g., carrots, some varieties of squash) and (3) those in which /3-cryptoxanthin and /3-carotene are the major contributors (e.g., cashew, apple, peach, persimmon, loquat) (60). 

When green leafy vegetables are under analysis, the carotenoids are prone to photoisomerization by the sensitizing action of coextracted chlorophylls. 

In another study (38) on coronary primary prevention, the placebo-controlled trial of colestyramine resin in coronary heart disease (CHD), the serum carotenoids levels were found inversely related to CHD events. In the same study, there was no evidence of activity of Se and a-tocopherol, The authors concluded that there was no proof of a cause-and-effect relation and that it was possible that another constituent of the diet could be present together with /3-carotene in the same food products. Consequently, the final suggestion was to increase the consumption of yellow fruits and green leafy vegetables. 

One of the highest known concentrations of carotenoids occurs in crude palm oil. It contains about 15 to 300 times more retinol equivalent than carrots, green leafy vegetables, and tomatoes. All of the carotenoids in crude palm oil are destroyed by the normal processing and refining operations. Recently, improved gentler processes have been developed that result in a red palm oil that retains most of the carotenoids. The composition of the carotenes in crude palm oil with a total carotene concentration of 673 mg/kg is shown in Table 6-5. 

Lutein and zeaxanthin are the dominant carotenoids in the human retina (112). They represent about 36% and 18% of the total carotenoid content of the retina, respectively (101). M. oleifera contains high amounts of lutein, 24.8 mg/100 g edible fresh leaves (39). Carotenoid types - a-carotene and 3-carotene are up to 4.5 and 34 mg/100 g, respectively, while lycopene is not present inM. oleifera (44). In fresh leaves of M. oleifera of Tanzania, vitamin C (ascorbic acid) content can be as high as 204 mg/100 g fresh weight (113). On the other hand, in Pakistan vitamin C contents range between 36 and 43 mg/100 g (4). In terms of cooking stability, when 20 mg samples are cooked in 400 ml of water, the vitamin C content loss can be as high as 98.5%. However, smaller losses of vitamin C are observed when M. oleifera sample is cooked in less water. Since most leafy vegetables are cooked prior to consumption, it is recommended that M. oleifera leaves be cooked in small amounts of water for short periods to minimise loss of vitamin C (113). Essential Oils... 

Vitamin A and the associated carotenoids not only reduce the risk of cancer but also strongly inhibit tissue oxidation and free radical damage. Dietary sources of Vitamin A and carotenoids include fish liver oils, dark green leafy vegetables, yellow and red vegetables, beets, spirulina, and garlic. 

---