Founding member of the antioxidant carotenoid family
A carotenoid known as an anti-oxidant and as a provitamin A, because it is one of the most important precursors of vitamin A in the body. Beta-carotene converts to vitamin A in the body and is needed for healthy sight, skin and hair. A pro-vitamin to Vitamin A, thought to have anti-cancer effects that could boost immunity, improve vision, support holistic healing and help prevent heart disease. Beta-carotene is believed to contain no toxic side-effects like Vitamin A. Beta-carotene is known for its yellow-orange pigment.
There are 2 ways in which Beta-carotene can be converted to vitamin A: either by cleavage at the centre or by breaking the molecule down from one end. The later is thought to be most important biologically. The breakdown of beta-carotene occurs in the walls of the small intestine (intestinal mucosa) and is catalysed by the enzyme beta-carotene dioxygenase. The retinol formed is stored in the liver as retinyl esters. The vitamin A conversion factor for beta-carotene in carrots is 15 units to one and for spinach it is 22 units to one.
History: First isolated by Wackenroder in 1831, and many other carotenoids were discovered and named during the 1800s, although their structures were still unknown.They have been synthesised for use as food colorings since the 1950s. In 1907 the empirical formula of beta-carotene, C40H56, established by Willstatter and Mieg.
Paul Karrer was responsible for elucidating the chemical structure of carotenoids and he showed that some of these substances are transformed in the animal body into vitamin A. In 1930, it led to the establishment of the constitutional formula for b-carotene, the chief precursor of vitamin A; this was the first time that the structure of any vitamin or provitamin had been established. It led to the clarification of the structure of vitamin A itself.
Technicals: A member of a family of molecules known as the carotenoids with a basic structure comprised of isoprene units. These units are joined end-to-end to give a conjugated chain, common to all carotenoids. The two centre isoprene units are joined differently to the others ("head-to-head" rather than "head-to-tail") so that the chain has a centre of symmetry. It is made up of 8 isoprene units, which are cyclised at each end.
Sources: Found in vegetables and fruits and most abundant in carrots, pumpkins, apricots and nectarines. Dark green vegetables, spinach and broccoli (the orange colour is masked by the green color of chlorophyll).
Synergist: Other Antioxidants such as Vitamin C and Selenium
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