Brief Introduction and Preparation of Ascorbic Acid

Ascorbic acid picture Image: Ascorbic acid structural formula Brief Introduction and Preparation of Ascorbic Acid Ascorbic acid, also known as vitamin C, is a water-soluble vitamin, generally white flake crystalline or crystalline powder, with a sour taste, according to the chemical source network information, ascorbic acid chemical structure formula is C6H8O6, CAS number 50-81-7, melting point 190~ 194 degrees Celsius, relative molecular weight 176.124, soluble in water, slightly soluble in ethanol, but insoluble in benzene, ether, petroleum ether, chloroform, oils and fats. The solubility of vitamins varies greatly with temperature, 35 at 5 degrees Celsius and 40 at 45 degrees Celsius, but when it reaches 100 degrees Celsius, the solubility is as high as 80. Ascorbic acid molecules generally appear as monogenic acids, and the pH value of the aqueous solution decreases with the increase of concentration. When the concentration is 0.5%, the pH value is 3, and when the concentration is increased to 5%, the pH value is correspondingly reduced to 2. Ascorbic acid is relatively stable in the dry state, and it will undergo oxidation reaction when exposed to light or air, and the color will become darker. Its aqueous solution is also easily oxidized and decomposed into dehydroascorbic acid. Since ascorbic acid itself is acidic, it will also rapidly oxidize in alkaline or neutral solutions, generating dehydroascorbic acid. In acidic solutions, it is relatively stable. Ascorbic acid got its name because its appearance eliminated a long-standing human nightmare, scurvy. It was long discovered that fruits and fresh vegetables were effective in treating scurvy, but the cause was not known until Zelji discovered the existence of ascorbic acid in 1927 and determined its structure around 1930. Ascorbic acid is widely found in fresh fruits and vegetables, citrus, lemon (ascorbic acid crystals were extracted from lemon juice in 1932), dates, peppers, tomatoes, bitter gourd and other foods. General mammals can synthesize vitamins through the liver, but as primates, humans cannot synthesize themselves and can only be supplemented by food or drugs. Ascorbic acid participates in a variety of metabolic reactions in the body: 1. Promote collagen synthesis. Ascorbic acid must be present in the synthesis process of collagen, otherwise the reaction cannot proceed. Collagen is an important component of human connective tissue, accounting for one-third of human fat and is an important guarantee for human health 2. Participates in cholesterol conversion. As a coenzyme, ascorbic acid (vitamin C) can assist 7-alpha-hydroxylase in promoting cholesterol conversion to bile acids. At the same time, ascorbic acid itself can also inhibit low-density lipoprotein and increase high-density lipoprotein, thereby reducing the total cholesterol content. During the synthesis of adrenal cortical hormones, ascorbic acid is also a necessary substance for part of the hydroxylation step. 3. Participates in the metabolism of aromatic amino acids. Ascorbic acid, as a key substance in many hydroxylation steps, participates in the hydroxylation process of phenylalanine (Phe) to tyrosine (Tyr), the hydroxylation process of tyrosine to catecholamine (catecholamine), and the decomposition of tyrosine into partial hydroxylation in urinary melanic acid. Ascorbic acid is also involved in the conversion of tryptophan (Trp) to serotonin (5-HT) 4. Participate in redox reactions in the body, playing an important role in biological oxidation and reduction and cellular respiration. Ascorbic acid can reduce erythrocyte methemoglobin to hemoglobin, restore oxygen delivery function, and make trivalent iron into divalent iron through reduction reaction, which greatly improves the absorption rate of iron, thereby improving the efficiency of iron use by the liver, and treating various iron deficiency anemia. The role of ascorbic acid is so extensive that it is also often used as an antioxidant in foods, such as beverages, confectionery, dairy products, meat products, and flour improvers, and is often added to foods. Vitamin C (ascorbic acid) can improve human immunity, but it should not be used in excess, which can lead to vitamin C poisoning, often manifested as polyuria, diarrhea, skin rash in the short term, and oxalic acid or uric acid stones in the long term. In scientific research, ascorbic acid is often studied in depth. In order to meet the needs of daily scientific research, you can purchase the corresponding brand reagents in Huayuan Mall, but you can also extract them from fruits, vegetables, and green tea rich in vitamin C, or use the Leichstein method to prepare them yourself. 1. Under the action of Nguanlai nickel catalyst, pressure is applied to hydrogenate glucose to form sorbitol. 2. Carry out aerobic fermentation of sorbitol with Acetobacter suboxydans to generate L-sorbitol 3. Using sulfuric acid as a catalyst, L-sorbose and acetone are condensed to obtain diacetone-L-sorbitol 4. Oxidation of diacetone-L-sorbitol with potassium permanganate to obtain diacetone-L-gluconic acid under alkaline conditions 5. Using sulfuric acid as catalyst, diacetone-L-gluconic acid and methanol are esterified to obtain methyl 2-keto-L-gluconate 6.Methyl 2-keto-L-gluconate interacts with sodium methoxide to form sodium L-ascorbate 7. Finally, it is heated with hydrochloric acid to generate ascorbic acid (vitamin C). Ascorbic acid preparation References: 1. Wang Fang. Principles and Technologies of Food Nutrition and Health Care: China Light Industry Press, 1996 2. Physiological function and application of vitamin C. Food bioengineering, graduation thesis. 3. Song Lihua, Editor-in-Chief of Ren Xiaoyan. Analytical Chemistry Technology: Chongqing University Press, 2016.01: 107-108 4. Hu Qiuhong, editor-in-chief of Xu Liya. Food Nutrition and Hygiene: Beijing Institute of Technology Press, 2011.02: 54-55 5. Zhao Anda, Liu Xipeng, Wang Xin, Sun Juan, Wu Qiaomin, Zhang Meifang. Research progress on the association between vitamins and urinary calculi [J]. Shanghai Medicine, 2019,40 (17): 19-24.. CNKI [citation date 2020-03-23] 6. Editor-in-chief Miao Qing. Scientific vitamin supplementation: Jilin Science and Technology Press, 2003.08: 121-122 7. An Jiaju, editor-in-chief; Bao Wenchu, Wang Boying, Li Shunping, co-editors. Dictionary of Practical Fine Chemicals. Beijing: China Light Industry Press. 8. Kong Baohua et al. Application of ascorbic acid in food. Food Industry. 1995, 2:51-52. 9. Zhang Shouwen, Editor-in-Chief. Chinese Bakery Dictionary • Raw and Auxiliary Ingredients and Food Additives Volume. Beijing: China Light Industry Press. 10. High margins, etc. New applications of ascorbic acid. Advances in pharmacy. 2000, 1:24-27.