الوصف

Introduction: Although certain animals can synthesize certain vitamins and all animals needing vitamin D can manufacture it from ergosterol in the presence of u.v. light, the precise mechanism of action of many vitamins is still poorly understood. Small amounts of vitamins are essential for the regulation of all bodily processes. With the exception of vitamin D, the human body cannot make its own vitamins, and some cannot be stored. Vitamins must therefore be obtained from a food on a daily basis. A person's diet must provide all the necessary vitamins. Vitamin C or Ascorbic acid is the enolic form of *-oxo-L-gulofuranolactone. It can be prepared by synthesis from glucose, or extracted from plant sources such as rose hips, blackcurrants or citrus fruits. It is easily oxidized in air. It is essential for the formation of collagen and intercellular material, bone and teeth and for the healing of wounds. It helps maintain elasticity of the skin aids the absorption of iron and improves resistance to infection. It is used in the treatment of scurvy. May prevent the occurrence and development of cancer. Man is one of the few mammals unable to manufacture ascorbic acid in his liver. Good sources of Vitamin C are Broccoli, Brussels sprouts, cauliflower, cabbage, mangetout, green leafy vegetables, red peppers, chilies, watercress, parsley, blackcurrants, strawberries, kiwi fruit, guavas, and citrus fruit. Physical & Chemical Properties.: It is odorless or almost odorless. It has a pleasant, sharp acidic taste. It is freely soluble in water and sparingly soluble in ethanol. It is practically insoluble in ether and chloroform. Ascorbic acid has pKa values of 4.2 and *1.6. Ascorbic acid has a melting temperature of **0�C with decomposition. A 5% solution in water has a pH of 2.*- 2.5. In impure preparations and in many natural products the vitamin oxidizes on exposure to air and light.