Vitamin chemical structure

L-Ascorbic acid, better known as vitamin C, has the simplest chemical structure of all the vitamins (Figure 18.30). It is widely distributed in the animal and plant kingdoms, and only a few vertebrates—humans and other primates, guinea pigs, fruit-eating bats, certain birds, and some fish (rainbow trout, carp, and Coho salmon, for example)—are unable to synthesize it. In all these organisms, the inability to synthesize ascorbic acid stems from a lack of a liver enzyme, L-gulono-y-lactone oxidase. 

Vitamin A (retinol) and its naturally occurring and synthetic derivatives, collectively referred to as retinoids (chemical structure), exert a wide variety of profound effects in apoptosis, embryogenesis, reproduction, vision, and regulation of inflammation, growth, and differentiation of normal and neoplastic cells in vertebrates. 

Since many essential nutrients (e.g., monosaccharides, amino acids, and vitamins) are water-soluble, they have low oil/water partition coefficients, which would suggest poor absorption from the GIT. However, to ensure adequate uptake of these materials from food, the intestine has developed specialized absorption mechanisms that depend on membrane participation and require the compound to have a specific chemical structure. Since these processes are discussed in Chapter 4, we will not dwell on them here. This carrier transport mechanism is illustrated in Fig. 9C. Absorption by a specialized carrier mechanism (from the rat intestine) has been shown to exist for several agents used in cancer chemotherapy (5-fluorouracil and 5-bromouracil) [37,38], which may be considered false nutrients in that their chemical structures are very similar to essential nutrients for which the intestine has a specialized transport mechanism. It would be instructive to examine some studies concerned with riboflavin and ascorbic acid absorption in humans, as these illustrate how one may treat urine data to explore the mechanism of absorption. If a compound is... 

Snell, E. E., Chemical structure in relation to biological activities of vitamin B8. Vitamins and Hormones 16, 77-125 (1958). 

The primary chemicals of interest in chilies are capsaicinoids, namely capsaicin (0.02%) and dihydrocapsaicin (figure 8.11). Also found are flavonoids, carotenoids (capsanthin), steroid saponins (capsicidin), and ascorbic acid or vitamin C (0.2%). Capsaicin has a vanilloid chemical structure. Mechanisms of Action... 

Compared with other vitamins, the chemical structures of both folic acid and B12 are complex. They are prosthetic groups for the enzymes that catalyse the transfer of the methyl group (-CH3) between compounds (one-carbon metabolism). The -CH3 group is chemically unreactive, so that the chemistry for the transfers is difficult, requiring complex structures for catalysis. 

Vitamins are vital for normal metabolism in body. They vary in their chemical structure and are supplied in very small quantity in diet, because they are not synthesized in body or their rate of production is not sufficient for maintenance of health. Vitamin deficiency leads to development of deficiency symptoms. Different vitamin preparations are available for treatment and prophylaxis. Most of the vitamins are nontoxic but on chronic administration can cause toxicity especially vitamin A and D. 

Little data is available on the interaction of protein modification for improved functionality and vitamin bioavailability from modified food-stuffs. Some water-soluble and fat-soluble vitamins are protein-bound in their transport, storage and/or active forms. Therefore, methods used to cause dramatic alteration of protein conformation or chemical structure can be assumed to alter some vitamins as well. 

Mammals have several classes of hormones, distinguishable by their chemical structures and their modes of action (Table 23-1). Peptide, amine, and eicosanoid hormones act from outside the target cell via surface receptors. Steroid, vitamin D, retinoid, and thyroid hormones enter the cell and act through nuclear receptors. Nitric oxide also enters the cell, but activates a cytosolic enzyme, guanylyl cyclase (see Fig. 12-10). 

Ascorbic acid ( Vitamin C ). The crystal structure of this substance cannot be said to be established with the certainty and precision we associate with those already described nevertheless, there is no reason to doubt that the structure suggested by Cox and Goodwin (1936) on the basis of p, limited study of the X-ray reflections is essentially correct. The work is described here because this crystal structure presents some very interesting and instructive features. It is also historically interesting because a preliminary study by optical and X-ray methods played a part in the elucidation of the chemical structure of this biologically important substance. (Cox, 1932 a Cox, Hirst, and Reynolds, 1932 Cox and Hirst, 1933.)... 

Knowledge of the chemical structures of the major vitamins was acquired during the 30 years after 1920, and some were identified as known compounds. They were classified as fat-soluble and water-soluble vitamins. The only heterocyclic compounds in the former class are the tocopherols (vitamin E). They were discovered through their action in preventing sterility in rats, but they appear to play an important part in the metabolism of skeletal muscle. Vitamin E deficiency appears to occur rarely in man, but vitamin E therapy is tried in a number of clinical disorders. The tocopherols may be isolated from vegetable oils, and synthetic a-tocopherol (61) is made by condensing trimethylhydroquinone with phytol or phytyl halides (Scheme 2). For medicinal use they may be converted into their acetates or succinates. 

Figure 5.23 Chemical structures of 7-dehydrocholesterol and vitamin D. The photochemical reaction is an electrocyclic ring opening...

Many of these so-called natural products were first used without any knowledge of their chemical composition. As organic chemistry developed, though, chemists learned how to work out the structures of the compounds in natural products. The disease-curing properties of limes and other citrus fruits, for example, were known for centuries but the chemical structure of vitamin C, the active ingredient, was not determined until 1933. Today there is a revival of interest in folk remedies, and a large effort is being made to identify medicinally important chemical compounds found in plants. 

Fig. 15.7. a Chemical structures of vitamin E (a-TH) and vitamin E acetate (a-TAc) as indicated, b Confocal Raman spectra of skin after topical application of 60% a-TAc in octanol were acquired every 2 pm to an overall depth of 60 pm. The first 15 spectra of skin in the 450-1050 cm-1 range are shown, c Raman spectra of the 400-700 cm-1 region for pure vitamin E (a-TH) and pure vitamin E acetate (a-TAc) as marked... 

Fig. 9.4 Chemical structures of cellular lipids that act as endogenous antioxidants. Choline plasmalogens (a) ethanolamine plasmalogens (b) ganglioside (c) and vitamin E (a-tocopherol) (d)...

Fig. 9.5 Chemical structures of low molecular weight antioxidants Melatonin (a) ascorbic acid (Vitamin C) (b) glutathione (c) lipoic acid (d) a-tocopherol (Vitamin E) (e) and a-tocotrienol (f)...

Vitamins comprise a diverse group of organic chemicals that the body needs to facilitate specific metabolic and biosynthetic processes.4 In many cases, vitamins act as enzymatic cofactors that is, the vitamin works directly with the enzyme to catalyze a specific chemical reaction. In other situations, the vitamin forms an essential component of a chemical structure or species that is needed for a specific chemical reaction. The body typically needs small amounts of vitamins to promote normal growth and development, and to maintain optimal health throughout adulthood.32... 

Blueberries contain condensed tannins that help prevent urinary tract infections. Blueberries contain Anthocyanin (which is responsible for its deep blue color), which is a flavonoid, a plant antioxidant (see Chapter 8 and Chapter 31). Flavonoids such as anthocyanin found in blueberries have a different chemical structure compared to other common antioxidants such as vitamin C, which makes them three to four times more potent. Antioxidants neutralize the effects of free radicals, which are unstable molecules that can attack human cells and damage their DNA. 

Although the Catha edulis plant contains a number of chemicals, vitamins, and minerals, its main active ingredient is cathinone, an alkaloid with a chemical structure similar to ephedrine and d-amphetamine. Like amphetamine, it increases the levels of dopamine in the brain and acts as a mild stimulant. For this reason, khat is sometimes referred to as a natural amphetamine. 

The chemical structure of vitamin D3 is closely related to its precursor, 7-dehydrocholesterol, from which it is produced by a photochemical reaction. Therefore, vitamin Do is closely related structurally to the four-ring nucleus of steroids derived from the cyclopentanoperhydro-phenanthrene ring system. No vitamin D activity is noticed until the B ring of 7-dehydrocholesterol is opened between C-9 and C-10. Thus, vitamin D3 is a 9,10-seco steroid and its carbon skeleton is numbered accordingly (Scheme I). The important aspects of its chemistry center about the 5,6,7-cis-triene structure. The formula for vitamin D3 is C27H44O and its formula weight is 384.64. 

Therapeutic Function Calcium regulator. Vitamin Chemical Name 9,10-Secocholesta-5,7,10(19)-triene-l,3-diol Common Name la-Hydroxycholecalciferol la-Hydroxyvitamin D3 Structural Formula ... 

Chemical Name 5,6-Dimethylbenzimidazocyl cyanocobamide Common Name Vitamin B12 Structural Formula ... 

FIGURE 29.2 Chemical structure of vitamin C (ascorbic acid, (f )-5-[(5)-l,2-dihydroxyethyl]-3,4-dihydroxy-5 -furan-2-on). 

FIGURE 29.4 Chemical structure of vitamin A (all-trans retinol, (a//- )-3,7-dimethyl-9-(2,6,6-trimethyl-l-cyclohexenyl)-2,4,6,8-nonatetraen-l-ol). 

FIGURE 29.5 Chemical structure of vitamin D (calciferol, term for a collection of fat-soluble steroid-like substances that are regulating the calcium and phosphate metabolism). Cholecalciferol (R =R2=R3=H), Calcitriol (R1=R2=OH, R3=H). 

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