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These compounds are water-soluble and, thus, cannot protect fats from oxidation: For this purpose, the fat-soluble esters of ascorbic acid with long-chain fatty acids (ascorbyl palmitate or ascorbyl stearate) can be used as antioxidant food additives. Sodium-dependent active transport process enables absorption of Ascorbic acid from the intestine.
At room temperature, α-tocopheryl acetate is a fat-soluble liquid. It has 3 chiral centers and thus 8 stereoisomers. It is made by esterifying α-tocopherol with acetic acid. 2R,4R,8R-isomer, also known as RRR-α-tocopheryl acetate, is the most common isomer used for various purposes. This is because α-tocopherol occurs in nature primarily as ...
A combination of water-soluble and fat-soluble antioxidants is ideal, usually in the ratio of fat to water. In addition, rancidification can be decreased by storing fats and oils in a cool, dark place with little exposure to oxygen or free radicals, since heat and light accelerate the rate of reaction of fats with oxygen.
Dehydroascorbic acid has been used as a vitamin C dietary supplement. [9] As a cosmetic ingredient, dehydroascorbic acid is used to enhance the appearance of the skin. [10] It may be used in a process for permanent waving of hair [11] and in a process for sunless tanning of skin. [12]
Some dietary fat is necessary to facilitate absorption of fat-soluble vitamins (A, D, E, and K) and carotenoids. [ 91 ] : 903 Humans and other mammals have a dietary requirement for certain essential fatty acids, such as linoleic acid (an omega-6 fatty acid ) and alpha-linolenic acid (an omega-3 fatty acid) because they cannot be synthesized ...
The digestion products consisting of a mixture of tri-, di- and monoglycerides and free fatty acids, which, together with the other fat soluble contents of the diet (e.g. the fat soluble vitamins and cholesterol) and bile salts form mixed micelles, in the watery duodenal contents (see diagrams on the right). [27] [29]
A C5-carboxylic acid side chain is appended to the former ring. The ureido ring, containing the −N−CO−N− group, serves as the carbon dioxide carrier in carboxylation reactions. [ 7 ] Biotin is a coenzyme for five carboxylase enzymes, which are involved in the catabolism of amino acids and fatty acids , synthesis of fatty acids , and ...
Mechanism for acid-catalyzed hydrolysis of an amide. Upon hydrolysis, an amide converts into a carboxylic acid and an amine or ammonia (which in the presence of acid are immediately converted to ammonium salts). One of the two oxygen groups on the carboxylic acid are derived from a water molecule and the amine (or ammonia) gains the hydrogen ion.