Vitamin A precursors

K. Mbnzel, ia. C. Bauemfeiud, ed.. Carotenoids as Colorants and Vitamin A Precursors, Technological and Nutritional Applications, Academic Press, Inc., New York, 1981, pp. 781-813. 

Many carotenoids function in humans as vitamin A precursors however, not all carotenoids have provitamin A activity (Table 3). Of the biologically active carotenoids, -carotene has the greatest activity. Despite the fact that theoretically one molecule of -carotene is a biological source of two molecules of vitamin A, this relationship is not observed and 6 p.g -carotene is equivalent to 1 p. vitamin A. Although -carotene and vitamin A have complementary activities, they caimot totally replace each other. Because the conversion of -carotene to vitamin A is highly regulated, toxic quantities of vitamin A cannot accumulate and -carotene can be considered as a safe form of vitamin A (8). 

Therapeutic Function As a vitamin A precursor sunscreen agent Chemical Name f3-Carotene... 

Bauernfeind, J.C., Carotenoids as Colorants and Vitamin A Precursors, Academic Press, New York, 1981. 

In the Unites States, the daily intake of 3-carotene is around 2 mg/day Several epidemiological studies have reported that consumption of carotenoid-rich foods is associated with reduced risks of certain chronic diseases such as cancers, cardiovascular disease, and age-related macular degeneration. These preventive effects of carotenoids may be related to their major function as vitamin A precursors and/or their actions as antioxidants, modulators of the immune response, and inducers of gap-junction communications. Not all carotenoids exert similar protective effects against specific diseases. By reason of the potential use of carotenoids as natural food colorants and/or for their health-promoting effects, research has focused on better understanding how they are absorbed by and metabolized in the human body. 

Bauerfeind, J.C., Carotenoid vitamin A precursors and analogs in foods and feeds, J. Agric. Food Chem., 20, 456, 1972. 

Sometimes, natural supplies and synthetic production lines are in competition. An example is /1-carotene (1), traditionally used as food colorant, but nowadays increasingly applied as a health ingredient anti-oxidant and vitamin A precursor [6],... 

L B. Supplement with vitamin A. Vitamin A deficiency symptoms include night blindness that can lead to corneal ulceration. This deficiency can occur in patients with impaired liver storage or fat malabsorption. Dairy products, such as milk, are a good source of vitamin A. (3-Carotene, a vitamin A precursor, is found in pigmented vegetables, such as carrots. When a deficiency is diagnosed, it is appropriate to treat the patient with a supplement rather than to rely on increased consumption of vitamin A-rich foods. A patient with pancreatic disease and malabsorption syndrome will need parenteral supplementation. 

Orsat, B. Wirz, B. Bishof, S. (1999) A continuous lipase-catalyzed acylation process for the large-scale production of vitamin A precursors. Chimia, 53, 579-84. 

Vitamin A (retinol, 6.1) is the parent of a range of compounds known as retinoids, which possess the biological activity of vitamin A. In general, animal foods provide preformed vitamin A as retinyl esters (e.g. 6.5, which are easily hydrolysed in the gastrointestinal tract) while plant foods provide precursors of vitamin A, i.e. carotenoids. Only carotenoids with a /3-ionone ring (e.g. /1-carotene) can serve as vitamin A precursors. /3-Carotene (6.6)... 

Vitamin A Precursor to rhodopsin, a chemical used for vision assists in inhibiting bacterial and viral infections Night blindness (retinol)... 

The only vitamins likely to be found in unfortified soft drinks are vitamin C (either added as an antioxidant or deriving from fruit materials) and vitamin A precursor (beta-carotene, added as a colour). However, soft drinks provide a good medium for vitamin fortification, the limitations being solubility (for fat-soluble vitamins), flavour impairment (for example the meaty notes of thiamine) and stability. 

ACE drinks, containing beta-carotene (vitamin A precursor) and vitamins C and E. These materials are antioxidants and there is evidence that eliminating free radicals in the body will protect against cancer and cardiovascular diseases, particularly in older people. Suggested levels to... 

It is well-known that plants do not synthesize vitamin A. Also, animals can only synthesize vitamin A from p-carotene or carotenoids in which one-half of the molecule is like p-carotene. In nature, the vitamin A precursor comes either from plants or microorganisms. The most common sources of vitamin A in citrus are a- and p-carotenes and p-cryptoxanthin. In addition to the above name carotenoids, p-apo-8 -carotenal in citrus peel could be a source of provitamin A. However, the peel is not usually consumed. Provitamin A compounds are cleaved to form vitamin A aldehyde in the intestine by p-carotene 15,15 -oxygenase (Figure 4) (54). Aldehyde reductase reduces the aldehyde to the all trans-vitamin A. p-Carotene is cleaved between the 15,15 carbon... 

Carotenoids, a class of yellow to deep-red pigments present in many commonly eaten fruits and vegetables, have been hypothesized to play a role in the prevention of chronic diseases such as cancer and heart disease. Most research to date has focused on the relationship between P-carotene and lung cancer. Lung cancer is one of the most common cancers in the U.S., and P-carotene was initially the most thoroughly studied carotenoid because of its role as a vitamin A precursor (Cooper et al., 1999). 

Therapeutic Function Vitamin A precursor, Sunscreen agent Chemical Name p-Carotene Common Name -Structural Formula ... 

Several terpenoids have been evaluated for their inhibitory effects on EBV-EA activation induced by TPA. Table 6 shows the inhibitory effects of monoterpenoids [70,71], sesquiterpenoids [20,119-123], diterpenoids [21,123-131], and meroterpenoids [117] against TPA (32 pmol, 20 ng)-induced EBV-EA activation in Raji cells. The inhibitory effects were compared with that of [3-carotene, a vitamin A precursor that has been studied intensively in cancer chemoprevention using animal models [2,4]. All of the terpenoids tested caused higher viability (60-80%) of Raji cells even at mol ratio of compound to TPA = 1000 1 indicating their very low cytotoxicity at that high concentration (refer to Table 6). 

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