VitaminE family

Para-amino benzoic acid (PABA) is considered to be in the B-complex vitamin family. The human body can make it from folic acid, since PABA forms the middle part of that vitamin ... 

Vitamins are minor components of foods that play an essential role in human nutrition. Many vitamins are unstable under certain conditions of processing and storage (Table 9-1), and their levels in processed foods, therefore, may be considerably reduced. Synthetic vitamins are used extensively to compensate for these losses and to restore vitamin levels in foods. The vitamins are usually divided into two main groups, the water-soluble and the fat-soluble vitamins. The occurrence of the vitamins in the various food groups is related to their water-or fat-solubility. The relative importance of certain types of foods in supplying some of the important vitamins is shown in Table 9-2. Some vitamins function as part of a coenzyme, without which the enzyme would be ineffective as a biocatalyst. Frequently, such coenzymes are phosphorylated forms of vitamins and play a role in the metabolism of fats, proteins, and carbohydrates. Some vitamins occur in foods as provitamins—compounds that are not vitamins but can be changed by the body into vitamins. Vitamers are members of the same vitamin family. 

Vitamers are chemically similar substances that have a qualitatively similar vitamin activity. Thus, vitamin D refers to ergocalciferol (Da) and cholecalciferol (D3) and sometimes to their 25-hydroxy- and 1,25-dihydroxy derivatives (Chapter 37). Similarly, pyridoxine (pyri-doxol), pyridoxal, and pyridoxamine are vitamin Be vitamers, riboflavin is the active form of vitamin Ba and cobalamin is vitamin Bia- The members of a particular vitamin family are functionally interchangeable and protect against deficiency symptoms for that vitamin. A vitamin and its corresponding deficiency disease are related as follows ... 

Depeint, F., Bruce, W.R., Shangari, N., Mehta, R., and O Brien, P.J., 2006. Mitochondrial function and toxicity Role of the B vitamin family on mitochondrial energy metabolism. Chemico-Biological Interactions. 163 94— 112. 

This review attempts to collate clues to new relationships and functions of pterinoids its point of departure is the exhaustive treatment of PABA by Wright and Taormina (1954), and of the folic vitamin family by Stok-stad et al. (1954). Uses of microbial systems and the comparative biochemistry of pterinoids will be emphasized. The well-established folic-... 

Naphthalenediol. This diol can be prepared by the chemical or catalytic reduction of 1,4-naphthoquinone. Both the diol and quinone are of interest because of their relation to the vitamin K family. Carboxylation of 1,4-naphthalenediol with CO2—K2CO2 followed by neutralization gives... 

Biochemical Reactions. The quinones in biological systems play varied and important roles (21,22). In insects they are used for defense purposes, and the vitamin K family members, eg, vitamin [11104-38-4] (32) and vitamin [11032-49-8] (33), which are based on 2-meth5l-l,4-naphthoquiaone, are blood-clotting agents (see Vitamins, vitamin k). 

Vitamin E was first described ia 1922 and the name was originally applied to a material found ia vegetable oils. This material was found to be essential for fertility ia tats. It was not until the early 1980s that symptoms of vitamin E deficiency ia humans were recognized. Early work on the natural distribution, isolation, and identification can be attributed to Evans, Butt, and Emerson (University of California) and MattiU and Olcott (University of Iowa). Subsequentiy a group of substances (Eig. 1), which fall iato either the family of tocopherols or tocotrienols, were found to act like vitamin E (1 4). The stmcture of a-tocopherol was determined by degradation studies ia 1938 (5). 

Vitamin D is a family of closely related molecules that prevent rickets, a childhood disease characterized by inadequate intestinal absorption and kidney reabsorption of calcium and phosphate. These inadequacies eventually lead to the demineralization of bones. The symptoms of rickets include bowlegs,... 

Dam, along with Karrar of Zurich, isolated the pure vitamin from alfalfa as a yellow oil. Another form, which was crystalline at room temperature, was soon isolated from fish meal. These two compounds were named vitamins Kj and K2. Vitamin K9 can actually occur as a family of structures with different chain lengths at the C-3 position. 

Vitamin E actually consists of a family of compounds, the most active of which is a-tocopherol. The mechanism of the vitamin s action is not completely certain, but it seems likely that it might undergo hydrogen atom transfer reactions with free radicals to give a stable radical (see also Chapter 17, Problem 7). 

The juice of many fruits and particularly those of the citrus family contain appreciable quantities of ascorbic acid (vitamin C). It is not possible to examine... 

Epithelial calcium channel 1 (ECaCl), synonym TRJPV5, is a member ofthe TRP family of ion channels, implicated in vitamin D-dependent transcellular Ca2+ transport in epithelial cells ofthe kidney, placenta and the intestine. 

The term vitamin E describes a family of eight antioxidants, four tocopherols, alpha (a), beta ((3), gamma (y) and delta (8), and four tocotrienols (also a, (3, y, and 8). a-Tocopherol is present in nature in only one form, RRR a-tocopherol. The chemical synthesis of a-tocopherol results in eight different forms (SRR, SSR, SRS, SSS, RSR, RRS, RSS, RRR), only one of which is RRR a-tocopherol. These forms differ in that they can be right (R) or left (S) at three different places in the a-tocopherol molecule. RRR a-tocopherol is the only form of vitamin E that is actively maintained in the human body and is therefore the form of vitamin E found in the largest quantities in the blood and tissue. A protein synthesized in the liver (a-TTP alpha-tocopherol transfer protein) preferentially selects the natural form of vitamin E (RRR a-tocopherol) for distribution to the tissues. However, the mechanisms for the regulation of vitamin E in tissues are not known... 

A most important function of vitamin A is in the control of cell differentiation and mrnover. PsA-trans-retinoic acid and 9-cw-retinoic acid (Figure 45-1) regulate growth, development, and tissue differentiation they have different actions in different tissues. Like the steroid hormones and vitamin D, retinoic acid binds to nuclear receptors that bind to response elements of DNA and regulate the transcription of specific genes. There are two families of nuclear retinoid receptors the retinoic acid receptors (RARs) bind all-rrijw-retinoic acid or 9-c -retinoic acid, and the retinoid X receptors (RXRs) bind 9-cw-retinoic acid. 

Tocopherols and tocotrienols belong to the vitamin E family of compounds, which are potent antioxidants. The four isomers of tocotrienols (a-T3, P-T3, y-T3, 8-T3) are structurally related to their corresponding homologues of tocopherols (a-T, p-T, y-T, 8-T), but differ in their side-chain in that T3... 

Dedicated plants predominate in the bulk chemicals industry. They suit the manufacture of well-defined products using a determined technology. Any change of the product or the production process usually produces problems, which illustrates the inflexibility of a dedicated plant. A batch plant may also be operated as a dedicated plant to produce a single chemical. Some fermentation plants (with reactors of up to 200 m volume) are examples of dedicated batch plants for the production of a family of similar products. So-called bulk fine chemicals, i.e. compounds that are produced in larger quantities, are also manufactured in dedicated plants, e.g. vitamin C and aspirin (see Fig. 7.1-1). The va.st majority of batch plants, however, produce several chemicals. 

Vitamin E consists of a family of related compounds, the tocopherols. The most abundant in the American diet is 7-tocopherol and, although it is potentially superior in the detoxification of nitrogen dioxide, the biochemistry of a-tocopherol is considered more relevant to cardiovascular disease (Kayden and Traber, 1993). Vitamin E undoubtedly has several modes of action in vim. The most clearly understood of these, at the chemical level, is the role of a-tocopherol as an antioxidant. 

Some osteoporosis risk factors (see Table 53-1) are non-modifiable, including family history, age, ethnicity, sex, and concomitant disease states. However, certain risk factors for bone loss may be minimized or prevented by early intervention, including smoking, low calcium intake, poor nutrition, inactivity, heavy alcohol use, and vitamin D deficiency. 

---