Vitamin B>

Although several of the B vitamins constitute components of important coeiizymes, few investigations have been reported on the tissue concentrations of these vitamins in relation to age. 

The thiamine and cocarboxylase contents of heart muscle tissue were studied by Fornaroli (1951) in samples of 5 calves and 5 adult cattle. An average value of 0.030 mg % of free thiamine was found for both age groups, but a tendency to higher concentrations of cocarboxylase was observed in the immature (0.304 mg %) than in the adult animals (0.179 mg %). 

The results of riboflavin assays of 20 liver biopsy specimens from patients without liver disease were reported by Imanaga et al. (1953). The observed tissue contents showed no definite variation with age, the calculated mean values, expressed as milligrams per cent, being 20-29 years, 2.49 (N = 5) 30-39 years, 2.53 (V = 2) 40 9 years, 2.70 N = II) and 50-59 yesirs, 2.57 (V = 2)..  

An investigation was made by Schaus and Kirk (1956) of the total rilio-flavin tissue concentrations in 89 samples of the cerebral cortex, 86 samples of the heart, and 88 samples of the pectoral muscle derived from individuals ranging in age from 7 days to 92 years. The mean riboflavin values observed in human subjects for the various decades ai e presented in Table VIII. It will be seen from the recorded data that no significant changes with age were found in the riboflavin levels of the brain tissue (r = -f 0.14 t = 1.32) or skeletal muscle (r = —0.20 I = 1.08). A tendency was noted for the riboflavin values of the myocardium to decrease after the age of 80 years, but the number of samples derived from individuals above 80 years was too. small to permit definite conclusions in this respect the calculated coefficient of correlation (r), age myocardial riboflavin concentnition for the 86 samples analyzed, was —0.18 ( = 1.67). 

A study conducted by the same authors (Scliaus el al., 1955) on 100 samples of the thoracic descending aorta obtained from subjects ranging in age between 1 month and 83 years showed a definite decrease (Fig. 3) in the total riboflavin concentration of this tissue with age (r = —0.39 t = 4.20). 

Historically, humans have always had deficiencies of B-vitamins, although cereal grains are considered as an adequate source of these micronutrients. All B-vitamins, except Bi2 or cyanocobalamin, are naturally present in whole cereal grains (Chapter 3). The most common deficiencies are due to the lack of thiamin (Bj), niacin (B3), folic acid, and cyanocobalamin (Bjj). 

Thiamin or Bj has been recognized historically as the main cause of beriberi. Thiamin exists in free and bound forms (thiamin diphosphate and the protein-phosphate-thiamin complex). The bound forms are split in the gastrointestinal tract. The absorbed thiamin acts as a coenzyme in energy metabolism, mainly in the conversion of glncose to fats. In addition, it has high implications in the functioning of peripheral nerves (nerve impulses), brain, and muscles. Thiamin deficiency causes 

Riboflavin or B2 functions as part of enzymes called flavoproteins (FMN and FAD) critically important in respiration and cell metabolism. It plays a major role with thiamin and niacin in oxidation-reduction reactions. The deficiency of this vitamin is characterized by photophobia, angular lip stomatitis, dermatitis, and swelling of the tongue. 

Cyanocobalamin (Bjj), which is not present in grains and vegetables, also acts as a coenzyme, especially in bone marrow, neurons, and gastrointestinal epithelial cells. It is involved in hemoglobin formation, and plays a major role in the prevention of pernicious or macrocytic anemia (fewer and larger red blood cells than normal) and the maintenance of nerve tissues. The acute deficiency can also cause mental disorders. It is important to point out that cyanocobalamin is the only vitamin that requires a specific factor for its absorption. This factor is called intrinsic castle and is a muco- or glycoprotein secreted by the stomach. 

Folic acid (pteroyhnonoglutamic acid or PGA) exists in different forms in nature. These forms are changed to at least five active coenzymes critically important for the formation of purines and pyrimidines needed for the synthesis of DNA and RNA, the formation of hanoglobin, the interconversion of amino acids such as homocysteine to methionine, and the synthesis of choline from ethanolamine. Vitamins B,2, Bg, and C are essential as coenzymes for the activity of folacin in many metabolic processes. In practical terms, folic acid is required for cell division and reproduction, and prevents neural tube defects in newborns and cardiovascular diseases in adults. The cardiovascular protective role is because folacin and vitamin Bjj lower levels of homocysteine. 

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Procedure. A vitamin B complex tablet Is crushed and placed In a beaker with 20.00 mL of a 50% v/v methanol solution that Is 20 mM In sodium tetraborate and contains 100.0 ppm of o-ethoxybenzamIde. After mixing for 2 min to ensure that the B vitamins are dissolved, a 5.00-mL portion Is passed through a 0.45- xm filter to remove Insoluble binders. An approximately 4-nL sample Is loaded Into a 50- xm Internal diameter capillary column. For CZE the capillary column contains a 20 mM pH 9 sodium tetraborate/sodlum dIhydrogen phosphate buffer. For MEKC the buffer Is also 150 mM In sodium dodecylsulfate. A 40-kV/m electric field Is used to effect both the CZE and MEKC separations. 

Methanol, which elutes at 4.69 min, is included as a neutral species to indicate the electroosmotic flow. When using standard solutions of each vitamin, CZE peaks are found at 3.41 min, 4.69 min, 6.31 min, and 8.31 min. Examine the structures and p/Ca information in Figure 12.47, and determine the order in which the four B vitamins elute. 

Vitamin Bi is a cation and must, therefore, elute before the neutral species methanol thus it elutes first at 3.41 min. Vitamin B3 is a neutral species and should elute with methanol at 4.69 min. The remaining two B vitamins are weak acids that partially ionize in the pH 9 buffer. Of the two, vitamin Be is the stronger acid and is ionized (as the anion) to a greater extent. Vitamin Be, therefore, is the last of the vitamins to elute. 

The order of elution when using MEKC is vitamin B3 (5.58 min), vitamin Be (6.59 min), vitamin 82 (8.81 min), and vitamin Bi (11.21 min). What conclusions can you make about the solubility of the B vitamins in the sodium dodecylsulfate micelles ... 

Uses. Although cyanoacetic acid can be used in appHcations requiring strong organic acids, its principal use is in the preparation of malonic esters and other reagents used in the manufacture of pharmaceuticals, eg, barbital, caffeine, and B vitamins (see Alkaloids Hypnotics Vitamins). Cyanoacetic acid can be used for the preparation of heterocycHc ketones. 

Vitamins. The B-vitamins and vitamin K [84-80-0] are synthesized by mminal microorganisms and their supplementation is usually... 

Littie research is available regarding the amounts of vitamins and minerals needed by young mminants. However, it is common to supply calcium, phosphoms, trace-mineralized salt, and vitamins A, D, and E (4). In the absence of a functional mmen, B-vitamins and vitamin K should be... 

Spices and herbs can play an important indirect role in good nutrition. They are not high in nutrient values, but they help to increase the appeal and satisfaction of foods that are highly nutritious. Spices do contain fat, protein and carbohydrates, electrolytic minerals, iron and B vitamins, and others, but even the highest calorie spice, poppy seeds, contains only two to three calories per serving in normal use (12). 

Homocysteine arises from dietary methionine. High levels of homocysteiae (hyperhomocysteinemia) are a risk factor for occlusive vascular diseases including atherosclerosis and thrombosis (81—84). In a controlled study, semm folate concentrations of <9.2 nmol/L were linked with elevated levels of plasma homocysteiae. Elevated homocysteine levels have beea associated also with ischemic stroke (9). The mechanism by which high levels of homocysteine produce vascular damage are, as of yet, aot completely uaderstood. lateractioa of homocysteiae with platelets or eadothehal cells has beea proposed as a possible mechanism. Clinically, homocysteine levels can be lowered by administration of vitamin B, vitamin B 2> foHc acid. 

Brewers and bakers dried yeasts are used as dietary supplements. They contribute some protein and trace minerals, and some B vitamins, but no vitamin C, vitamin B 2 or fat-soluble vitamins. The glucose tolerance factor (GTE) of yeast, chromium nicotinate, mediates the effect of insulin. It seems to be important for older persons who caimot synthesize GTE from inorganic dietary chromium. The ceU wall fraction of bakers yeast reduces cholesterol levels in rats fed a hypercholesteremic diet. 

Uses. Inactive dried yeasts are used as iagredients ia many formulated foods baby foods, soups, gravies, and meat extenders as carriers of spice and smoke flavors and ia baked goods. Yeasts used ia the health food iadustry are geaeraHy fortified with minerals and contain higher concentrations of the B vitamins, especially thiamin, riboflavin, and niacia (see Vitamins). 

Therapeutic Function Treatment of B vitamin (folacin) deficiency... 

Riboflavin is one of the B vitamins. It is also known as vitamin B6 and is made up of carbon, hydrogen, nitrogen, and oxygen atoms. When 10.00 g of vitamin B6 is burned in oxygen, 19.88 g of C02 and 4.79 g of H20 are obtained. Another experiment shows that vitamin B6 is made up of 14.89% N. What is foe simplest formula for vitamin Be ... 

Niacin is one of foe vitamin B vitamins (B3). Estimate foe approximate values of foe indicated bond angles. Its skeleton (not its Lewis structure) is given below. 

FIGURE 5-14 Structures of some chemical species useful for designing anion-selective electrodes (a) Mn(III) porphyrin (b) vitamin Bi2 derivative (c) tri-n-octyltin chloride (d) lipophilic polyamine macrocyclic compound. 

One excellent UV protector for foods is PABA, a B vitamin. Likewise, many of the same antioxidants we ingest as health supplements—such as vitamin C and a similar chemical, erythorbic acid vitamin E and lecithin, a source of the important nutrients choline and inositol—occur naturally in food. 

Lecithin is often taken as a dietary supplement, since it contains the B vitamin choline. 

The B vitamin niacin is also known as nicotinic acid. The body converts various forms of the vitamin into forms it can use. 

Some sprays include vitamins such as tocopherols (vitamin E) or panthenol, which is metabolized in the skin to become pantothenic acid, a B vitamin. Since hair does not metabolize ( It s dead, Jim ), these sprays perform the functions of antioxidants (tocopherols). In other words, they add shine and moisture (panthenol) rather than perform their normal vitamin roles. Moisture helps prevent damage during combing. 

Many Coenzymes, Cofactors, Prosthetic Groups Are Derivatives of B Vitamins... 

The water-soluble B vitamins supply important components of numerous coenzymes. Many coenzymes contain, in addition, the adenine, ribose, and phosphoryl moieties of AMP or ADP (Figure 7-2). Nicotinamide and riboflavin are components of the redox coenzymes... 

Organic and inorganic prosthetic groups, cofactors, and coenzymes play important roles in catalysis. Coenzymes, many of which are derivatives of B vitamins, serve as shutdes. ... 

Four of the B vitamins are essential in the citric acid cycle and therefore in energy-yielding metabolism (1) riboflavin, in the form of flavin adenine dinucleotide (FAD), a cofactor in the a-ketoglutarate dehydrogenase complex and in succinate dehydrogenase (2) niacin, in the form of nicotinamide adenine dinucleotide (NAD),... 

Blacher J, Safar ME Homocysteine, folic acid, B vitamins and cardiovascular risk. J Nutr Health Aging 2001 5 196. 

C03-0074. Determine the molecular formula and calculate the molar mass of each of the following B vitamins ... 

The remaining molecules, vitamin C, pantothenic acid, and pyridoxamine, have comparatively large numbers of O—H and N—H groups. These groups allow each of these vitamin molecules to form many hydrogen bonds, so they are all water-soluble (all the B vitamins are soluble in water). 

Commercial green tea leaves contain ascorbic acid (vitamin C) about 280 mg per 100 g dried leaves. Vitamin E in tea leaves is around 24-80 mg/lOOg dry weight but, because of its lipophilicity, solubility is low in tea infusions. The content of B vitamins in tea is around 8-15 mg/lOOg (Cheng and Chen 1994). 

Micronutrients (mg/100 g) Water-soluble vitamins B-vitamins Thiamin 2.65 3.64 2.00... 

Natural products have been noted for their potential health benefits from time immemorial and are the basis of Ayurveda, an ancient Indian medical practice (Bushkin and Bushkin, 2002). However, the potential benefits of several natural products reside in one or two active ingredients. For example green tea stands for polyphenols, soy for soy estrogens, broccoli for isothiocyanates and grape seed for polyphenols. The beauty of rice bran is that there are more than 100 antioxidants, several categories of bioactive phytonutrients, such as IP6, polyphenols, phytosterols, tocotrienols, y-oryzanol, B vitamins, minerals and trace minerals in addition to fat, protein, fiber, polysaccharides and other nutrients. These phytonutrients and antioxidants of rice bran are believed to act at the cellular level, and their synergestic function is responsible for the positive health benefits. 

No significant quantity of the macronutrients nor of the vitamins for which U.S. Recommended Dietary Allowance (RDA) have been established can be obtained from the consumption of a cup of tea.110 The water-soluble B vitamins present are easily extractable. Eight percent extractabil-ity for a representative black tea blend is assumed.110... 

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