Thiamine naturally occurring forms

Thiazole is known to occur naturally in various forms. The most widely recognized thiazole lies in the essential vitamin Bi or thiamin in the form of its thiazolium salt. It is a water-soluble vitamin of the B complex. Thiamin pyrophosphate is the essential coenzyme in the enzymatic decarboxylation of pyruvate to aldehyde. 

Thiamine is found in nature in several forms—as free thiamine, the monophosphate, TPP, and probably as thiamine bound by an —S—— linkage to protein, and as the disulfide of TPP. The recent report of Reed and DeBusk indicates still another naturally occurring bound form of thiamine, lipothiamine, the amide of thiamine and a-lipoic acid. Many unsolved problems still remain. In the animal, although TPP constitutes 90% of the total thiamine content in some tissues, in others only 80% occurs as this form muscle may contain more than 50% as free thiamine. The total thiamine content of tissues varies from 10 Mg- per gram wet weight for liver to less than 1 Mg- for muscle and brain. 

Vitamin Bj Vitamin Bj was discovered in 1926 by Jansen and Do-NATH, who synthesized it in its crystalline form from rice bran. It was initially called aneurine due to its antipolyneuropathic effect. Because it contains sulphur, Windaus correctly renamed it thiamine in 1932, a term by which it is still known today. The stixicture of this vitamin was described by Williams and Grewe in 1936. It is made up of pyrimidine and thiazole. Thiamine occurs in nature as free thiamine and in the form of thiamine monophosphate, diphosphate and triphosphate. A maximum amount of 8 — 15 mg is absorbed daily in the proximal portion of the small intestine. In the case of oversupply, thiamine is neither stored nor intestinally absorbed. A regular intake, with a daily requirement of about 1 mg, is necessary. The major coenzyme is thiamine pyrophosphate (TPP). Thiamine deficiency may be caused by malnutrition, impaired absorption, alcoholism, antithiamines or a lack of magnesium. Magnesium is an important cofactor for the coenzyme thiamine pyrophosphate. 

Thiamin (86, vitamin Bi) (O Scheme 35) occurs in nature free and in phosphorylated form Its glycosides have not been identified in natural material. The artificial glycosylation of... 

A rational total synthesis is used for some simple alkaloids (adrenaline, theophylline, papaverine), low molecnlar peptide hormones (oxytocin, vasopressin), vitamins (biotin, folk acid, thiamine, riboflavin), phenolic acids (sahcyhc acid). It should, however, be observed that the synthetic substances are all racemic forms, whereas many natural products occur in the 1-form. 

All living organisms are able to phosphorylate thiamine, with the aid of ATP, to form thiamine pyrophosphate (TPP). This form of the vitamin is ubiquitous in nature, and predominates in animals and many yeasts. In many plants, however, free thiamine is the prevailing form. Very small amounts of thiamine monophosphate and triphosphate have been reported to occur in animal tissues, but confirmation is required. Only in milk appreciable amounts of thiamine monophosphate have been found. Under certain conditions the pyrophosphate ester of thiamine disulfide has been encountered in yeast. Its presence has also been claimed in animal tissues, but this again requires confirmation. 

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