Pro-vitamin A

Proved reserves Provesteen process Providencia stuarti Providencia stuartii Pro-vitamin A... 

Vitamins are classified by their solubiUty characteristics iato fat-soluble and water-soluble groups. The fat-soluble vitamins A, E, and K result from the isoprenoid biosynthetic pathway. Vitamin A is derived by enzymic cleavage of the symmetrical C q beta-carotene, also known as pro-vitamin A. Vitamins E and K result from condensations of phytyldiphosphate (C2q) with aromatic components derived from shikimic acid. Vitamin D results from photochemical ring opening of 7-dehydrocholesterol, itself derived from squalene (C q). 

Most carotenoids have no pro-vitamin A activity with the notable exceptions of P-carotene, and to a lesser extent a-carotene and P-cryptoxanthin. They act as macular pigments (lutein and zeaxanthin) and they have antioxidant and biochemical properties other than pro-vitamin A activity. 

Natural pigment production for food coloration includes the entire spectrum of biotechnologies. For example, biological production of carotenoid pigments has medical implications because carotenoids are nutritive (pro-vitamin A), antioxidant, and photoprotective. Carotenoids are produced alternately in agricultural systems (plants), industrial bioreactors (bacterial and fungi), and marine systems (cyanobacteria and algae). 

Paine, J.A. et al.. Improving the nutritional value of Golden Rice through increased pro-vitamin A content, Nat. Biotechnol. 23, 482, 2005. 

Wurtzel, E.T. et al.. Research towards improvement of the pro-vitamin A (carotenoid) content of rice endosperm, Int. Rice Res. Notes 21, 43, 1996. 

Almeida, L.B. and Penteado, M.V.C., Carotenoids with pro-vitamin A activity of carrots (Daucus carota L.) consumed in Sao Paulo, Brazil, Rev. Farm. Bioquim. Univ. S. Paulo, 23, 133, 1987. 

Pro-vitamin A cleavage and formation of retinoids via eccentric and central cleavage of p,p... 

Scott KJ and Rodriguez-Amaya D. 2000. Pro-vitamin A carotenoids conversion factors retinol equivalents-fact or fiction Food Chem 69 125-127. 

Potatoes are an excellent source of carbohydrates and contain significant amounts ofphosphorus, potassium, calcium, and vitamins, especially vitamin C. Potato protein content, at over 10%, is relatively close to that of wheat flour (11%) also, thanks to their lysine, methionine, cystine and cysteine contents, potatoes are a valuable supplement to cereal proteins. For instance, potatoes provide a significant source of proteins (10-15% of total requirements), a major source of vitamin C, an important source of energy, and also minerals like iron and other vitamins such as thiamin, nicotinic acid, riboflavin, and pro-vitamin A (p carotene) (Salunkhe and Kadam, 1991). 

In food, vitamin A exits in two forms preformed vitamin A (retinol and retinyl esters) in animal products and pro-vitamin A carotenoids... 

In addition to (3-carotene there are a variety of other C j pro-vitamin A carotenes that differ from (3-c.arotene in the nature of the terminal cyclic moieties. Thus, representing the right cyclic moiety as X, we can represent (3-carotene as X—(IP)2—(PI)2—X that yields two molecules of vitamin A or X—(IP)2—OH. Carotenes can have different cyclic moieties X (where X X) or no cyclic isoprene dimer moieties. Other C () pro-vitamin A carotenes that yield only one vitamin A molecule on oxidation include a-carotene, (3-cryptoxanthin, (3-c.arotene epoxide, echinenone and mutachrome (generalized structure X—(IP)2—(PI)2—X ) and y-carotene and torulene (X-(IP)2-(PI)4). 

Crocetin (C20) is a yellow (IP)2—(PI)2-derived dicarboxylic, acid (generalized structure -OOG-Gig-GOO-) from the styles of Crocus sativus (Iridaceae) (the saffron of Indian cooking and Buddhist robes). Grocin, the digentiobiose ester of crocetin, is water soluble, unlike other carotenoids which are lipophilic (fat soluble). Crocetin is a protein kinase inhibitor. Excess vitamin A (or excess pro-vitamin A) ingestion is toxic (dog liver consumption having caused the death of Sir Douglas Mawson s explorer companions in the Antarctic by this mechanism). 

Retinal] (carotene) Oxidation of Vitamin A (Retinol), in turn derived from pro-vitamin A carotenes PKC... 

Red palm oil is the richest source of readily available carotenoids and is, therefore, very useful as a pro-Vitamin A supplement. Crude palm oil contains 500-800 ppm of carotenoids, of which (3-carotene and a-carotene account for about 90% (approximately 2 1 w/w), and lycopene, phytoene, and zeacarotenes are inter alias the remaining carotenoids (60). Other vegetable oils contain much lower levels of carotenoids (<100 ppm), but these are removed during the bleaching step in... 

The mandatory fortification of margarine with Vitamin A is accomplished by the addition of p-carotene (pro-Vitamin A) and/or Vitamin A esters. The carotene level is adjusted for the desired color and the colorless esters (acetate, palmitate, etc.) are used to standardize the vitamin content. Addition of Vitamin D is optional. Fortification with Vitamin E is not permitted by the U.S. margarine standard, but recently some spreads fortified with Vitamin E have appeared in the marketplace in the United States, and fortification of both margarines and spreads has recently been done in Europe. The naturally occurring Vitamin E content of vegetable oil margarines available in the United States has been reported (227). 

Carotenoids are the major source of pro-vitamin A in our diet. Fortunately, they are relatively heat stable and do not suffer extensive loss during thermal processing. However, most carotenoids are sensitive to photoxidation and may lose their bright color under long exposure to light and oxygen. In intact fresh tomatoes, light can promote carotenoid biosynthesis (8). 

Palm carotenoids provide a source of pro-vitamin A and its orange-red colour is useful as a natural pigment for food preparations, margarines, biscuits and confectionery. Besides the role of providing a source of vitamin, carotenoids are considered to have anti-carcinogenic properties. 

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