Vitamin B - Thiamin

Determination of structural features. The ultraviolet spectrum has been of value in the determination of the structure of several vitamins. Thus the presence of an a-naphthoquinone system in vitamin K was first detected by this means. Also the 4-methylthiazole and the 2 5-dimethyl-6-aminop U idine system was first identified in vitamin B (thiamine). a- and /3-Ionones can be distinguished since the former contains two conjugated chromophores and the latta three conjugated chromophores. 

The SP procedure of water-soluble vitamins from multivitamin tablets is particularly challenging due to the diverse analytes of varied hydrophobicities and pfC. Water-soluble vitamins (WSVs) include ascorbic acid (vitamin C), niacin, niacinamide, pyridoxine (vitamin B ), thiamine (vitamin Bj), folic acid, riboflavin (vitamin B2) and others. While most WSVs are highly water soluble, riboflavin is quite hydrophobic and insoluble in water. Folic acid is acidic while pyridoxine and thiamine are basic. In addition, ascorbic acid is light sensitive and easily oxidized. The extraction strategy employed was a two-step approach using mixed solvents of different polarity and acidity as follows ... 

Vitamin B thiamine the precursor to the coenzyme thiamine pyrophosphate. 

K-Lor, Slow-K, Micro-K, Klorvess, others) (Table VI-5) Pyridoxine [Vitamin B ] Thiamine [Vitamin BJ... 

Health and Safety Factors. Malononiirilc is usually available as a solidified melt in plastic-lined drums. Remclting has to he done carefully because spontaneous decomposition can occur at elevated temperatures, particularly above lOO C. in the presence of impurities such as alkalies, ammonium, and zinc sails. Occupational exposure to malononitrile mainly occurs by inhalation of vapors and absorption through the skin. Malononitrile has a recommended workplace exposure limn of 8 mg/m Uses. Malononitrile is extensively used in the life sciences industry The most important products ate vitamin B (thiamine) and bensulfuron-melhyl. a sulfonyl urea herbicide. Most other product uses fall under the. V-containing heterocycles. 

T Kawasaki. Vitamin B, thiamine. In AP De Leenheer, WE Lambert, HJ Nelis, eds. Modem Chromatographic Analysis of Vitamins. 2nd ed. New York Marcel Dekker, 1992, pp 319-354. 

Jansen and Donath isolated vitamin B, (thiamine) from rice polishings. 

Vitamin B, [thiamin) Men 1.2 mg/d Women 1.1 mg/d Coenzyme in the metabolism of carbohydrates and certain amino acids prevents beriberi No adverse effects have been reported ... 

Some of the vitamins in the coeiizymc form associate tightly wdth specific enzymes, but not via a covalent linkage. Immediately after biosynthesis on the ribosome, enzymes do itot contain their cofactor, and these are called apoenzymes. An eitzyme containing its required cofactor is called a hoLoenzyme, With removal of the cofactor, the enzyme is also called an apoenzyme. The enzymes that exist in apoenzyme and holoenzyme forms include those that use vitamin Bx2, vitamin B, thiamin, and riboflavin-based cofactors. Enzymes that use niacin-based cofactors, folate, ascorbate, and vitamin K are not said to exist in apoenzyme and holocn-zyme forms. These enzymes bind their cofactors relatively weakly, and the cofactors behave in a manner similar to substrates. 

Vitamin B complex is the collective term for a number of water-soluble vitamins found particularly in dairy products, cereals and liver.Vitamin B (thiamine) is used by mouth for dietary supplement purposes and by injection in emergency treatment of Wernicke-Korsakoff syndrome. Vitamin B2 (riboflavin) is a constituent of the coenzyme FAD (flavine adenine dinucleotide) and FMN (flavine mononucleotide) and is therefore important in cellular respiration. Vitamin Be (pyridoxine) is a coenzyme for decarboxylases and transamination, and is concerned with many metabolic processes. Overdose causes peripheral neuropathy. It may be used medically for vomiting and radiation sickness and for premenstrual tension. Pyridoxine has a negative interaction with the therapeutic use of levodopa in parkinsonism by enhancing levodopa decarboxylation to dopamine in the periphery, which does not then reach the brain. The antitubercular drug isoniazid interferes with pyridoxine, and causes a deficiency leading to peripheral neuritis that may need to be corrected with dietary supplements. Vitamin B ... 

The ascorbic acid content in tamarind is very low and varies from 2-20 mg/lOOg (Lefevre, 1971 and Ishola et al, 1990, both cited in (5)). Tamarind frait pulp was reported to have a high content of vitamin B (thiamine, riboflavin and niacin) as well as a small amonnts of carotene and vitamin C (75). 

Long term usage of ethanol enhances the metabolic removal of vitamin B. (thiamin pyrophosphate). B deficiencies are known to result in polyneuritis, a neurological disorder, and beriberi, a cardiac problem. 

The direction of radical reactions that involve competitive, mixed-order kinetics could be changed as dose rate is increased. Bimolecular reactions would be favored in competition with unimolecular (or pseudo-unimolecular) reactions, because of the higher instantaneous radical concentrations. This effect could be encountered in lipids and in polymers. It is responsible for the greater retention of vitamin B] (thiamin) in pork when irradiated with electron beams than when irradiated with gamma rays (Figure 1) [6]. 

Hjorth N (1958) Contact dermatitis from vitamin B (thiamine). Relapse after ingestion of thiamine. Cross sensitization to cocarboxylase. J Invest Dermatol 30 261-264 Hjorth N (1961) Eczematous allergy to balsams. Acta Derm Venereol [Suppl] (Stockh) 41 46 Hjorth N (1967) Occupational dermatitis among veterinary surgeons caused by penetha-mate (benzyl-penicillin-B-diethyl-aminoethyl ester). Berufsdermatosen 15 163-175 Hjorth N (1972) Contact dermatitis from l,3-diiodo-2-hydroxypropane. Contact Dermatitis Newslett 12 322... 

A lack of thiamine in the diet causes the disease beri-beri, a nerve disease that in past years was common in the Orient. Just before 1900 it was found by Christiaan Eijkman (1858-1930) in Java that beri-beri occurred as a consequence of a diet consisting largely of polished rice, and that it could be cured by adding the rice polishings to the diet. In 1911 Casimir Funk assumed that beri-beri and similar diseases were due to lack of a substance present in a satisfactory diet and missing from a deficient diet, and he attempted to isolate the substance whose lack was responsible for beri-beri. He coined the name vitamin for substances of this sort (he spelled it vitamine because he thought that the substances were amines). The structure of vitamin B thiamine, was determined by R. R. Williams, E. R. Buchman, and their collaborators in 1936. 

Very different prosthetic groups that are involved in enzymatic catalysis and that are usually covalently linked or very tightly bound to the enzyme can be found. However, all of those carrying phosphorus are part of the class of the B vitamins (B, B2, B, and 6,2). For example, vitamin B (thiamin) is the precursor for synthesis of the prosthetic group thiamin pyrophosphate. It functions as a coenzyme, usually in conjunction with Mg2+, which is thought to complex to the pyrophosphate group (Chauvet-Monges et ai, 1981) in enzyme-catalyzed reactions of aldehyde removal or transfer. 

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