Riboflavin vitamin essentiality

Riboflavin (vitamin Bj) is chemically specified as a 7,8-dimethyl-10-(T-D-ribityl) isoalloxazine (Eignre 19.22). It is a precnrsor of certain essential coenzymes, such as flavin mononucleotide (FMN) and flavin-adenine dinucleotide (FAD) in these forms vitamin Bj is involved in redox reactions, such as hydroxylations, oxidative carboxylations, dioxygenations, and the reduction of oxygen to hydrogen peroxide. It is also involved in the biosynthesis of niacin-containing coenzymes from tryptophan. 

Several of the B vitamins function as coenzymes or as precursors of coenzymes some of these have been mentioned previously. Nicotinamide adenine dinucleotide (NAD) which, in conjunction with the enzyme alcohol dehydrogenase, oxidizes ethanol to ethanal (Section 15-6C), also is the oxidant in the citric acid cycle (Section 20-10B). The precursor to NAD is the B vitamin, niacin or nicotinic acid (Section 23-2). Riboflavin (vitamin B2) is a precursor of flavin adenine nucleotide FAD, a coenzyme in redox processes rather like NAD (Section 15-6C). Another example of a coenzyme is pyri-doxal (vitamin B6), mentioned in connection with the deamination and decarboxylation of amino acids (Section 25-5C). Yet another is coenzyme A (CoASH), which is essential for metabolism and biosynthesis (Sections 18-8F, 20-10B, and 30-5A). 

The many diverse components of milk have demonstrable effects on human health. Perhaps, the most commonly associated component of dairy food is that of dietary calcium. Dairy products provide the most significant contribution to dietary calcium intake in the modem Western diet. It has been estimated that dairy products contribute to >72% of dietary calcium in the United States (Huth et al., 2006). Calcium is an important mineral for maintenance of optimal bone health (Bonjour et al., 2009) and is an integral component of key metabolic pathways relating to, for example, muscle contraction both in skeletal and smooth muscle (Cheng and Lederer, 2008). Further, dairy products contribute other essential nutrients in the diet, such as proteins, phosphorus, potassium, zinc, magnesium, selenium, folate, riboflavin, vitamin B12, and vitamin A (Haug et al., 2007 Huth et al., 2006). Low-fat milk alternatives are fortified with vitamin A and vitamin D which is added to milk and fermented milk in many countries making it an important source for vitamin D (Huth et al., 2006). 

Riboflavin (vitamin B2) is an essential nutritional factor for humans (0.3-1.8 mg d-1) and animals (1-4 mg (kg diet)-1), who need it as a precursor for fla-voproteins [135]. It is produced at a volume of approx. 3 kt a-1, mainly as an animal feed additive. Approx. 300 t a-1 is used as a food additive and food colorant (E-101) and the remainder (500 t a-1) is used in pharmaceutical applications. Major producers are Roche (Switzerland), BASF (Germany), Archer-Daniels-Midland (USA) and Takeda (Japan). Microbial and chemical production have coexisted for many years but the latter has recently been phased out [136]. 

As a component of the coenz)une flavin adenine dinucleotide (FAD), riboflavin is essential for the energy-releasing reactions of the cell. The RDA for riboflavin is about 1.7 mg. Severe riboflavin deficiency is rare in most parts of the world, but a marginal deficiency of this vitamin is common even in the United States. Mild riboflavin deficiency leads to dry, cracked lips and other mild forms of dermatitis. In severe cases, however, riboflavin deficiency leads to extreme sensitivity to simlight and retarded growth in children. 

Vitamins are a well-known group of compounds that are essential for human health. Water-soluble vitamins include folate (vitamin B9) to create DNA. Folate also plays an important role in preventing birth defects during early pregnancy. Thiamine is the first vitamin of the B-complex (vitamin Bl) that researchers discovered. It allows the body to break down alcohol and metabolize carbohydrates and amino acids. Like many other B vitamins, riboflavin (vitamin B2) helps the body to metabolize carbohydrates, proteins, and fat. Niacin (vitamin B3) protects the health of skin cells and keeps the digestive system functioning properly. Pantothenic acid (vitamin B5) and biotin allow the body to obtain energy from macronutrients such as carbohydrates, proteins, and fats. Vitamin B6 (pyridoxine) acts as a coenzyme, which means it helps chemical reactions to take place. It also plays a vital role in the creation of nonessential amino acids. 

It should be noted in passing that higher animals have lost the ability to synthesize some of the coenzymes or parts of them. By definition, a vitamin is an essential substance that the body cannot make for itself and must acquire through its food. Humans cannot make pantothenic acid (vitamin B5) needed for coenz mie A, nicotinamide (vitamin B3) for NAD", riboflavin (vitamin B2) for FAD, thiamine (vitamin B,), folic acid (vitamin Be or M) or pyridoxal (vitamin Bg). We possess the ability to phosphorylate or otherwise convert the vitamins into active coenzymes. Some of these substances are also vitamins for insects, plus some others which higher animals can make themselves. 

Riboflavin (vitamin B ) plays an essential role in cellular metabolism, being the precursor of the co-enzymes flavin mononucleotide (FMN) and flavin adenine dinucleotide (FAD) that both act as hydrogen carriers in biological redox reactions involving enzymes such as NADH dehydrogenase. Once riboflavin is absorbed in the human body, the synthesis of these flavin co-enzymes is controlled by thyroid hormones that regulate the activities of the flavin biosynthetic enzymes (Rucker et al. 2001). 

In terms of amino acids bacterial protein is similar to fish protein. The yeast s protein is almost identical to soya protein fungal protein is lower than yeast protein. In addition, SCP is deficient in amino acids with a sulphur bridge, such as cystine, cysteine and methionine. SCP as a food may require supplements of cysteine and methionine whereas they have high levels of lysine vitamins and other amino acids. The vitamins of microorganisms are primarily of the B type. Vitamin B12 occurs mostly hi bacteria, whereas algae are usually rich in vitamin A. The most common vitamins in SCP are thiamine, riboflavin, niacin, pyridoxine, pantothenic acid, choline, folic acid, inositol, biotin, B12 and P-aminobenzoic acid. Table 14.4 shows the essential amino acid analysis of SCP compared with several sources of protein. 

Flavoprotein enzymes contain flavin mononucleotide (FMN) or flavin adenine dinucleotide (FAD) as prosthetic groups. FMN and FAD are formed in the body from the vitamin riboflavin (Chapter 45). FMN and FAD are usually tighdy—but not covalendy—bound to their respecdve apoenzyme proteins. Metalloflavopro-teins contain one or more metals as essential cofactors. 

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),... 

Flavins — Riboflavin is first of all essential as a vitamin for humans and animals. FAD and FMN are coenzymes for more than 150 enzymes. Most of them catalyze redox processes involving transfers of one or two electrons. In addition to these well known and documented functions, FAD is a co-factor of photolyases, enzymes that repair UV-induced lesions of DNA, acting as photoreactivating enzymes that use the blue light as an energy source to initiate the reaction. The active form of FAD in photolyases is their two-electron reduced form, and it is essential for binding to DNA and for catalysis. Photolyases contain a second co-factor, either 8-hydroxy-7,8-didemethyl-5-deazariboflavin or methenyltetrahydrofolate. ... 

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... 

Pantothenic acid and biotin were thus found to be growth factors for yeast. Like riboflavin these molecules are incorporated into larger molecules in order to exert their essential metabolic function. Unlike the other vitamins there has been no evidence of pathological signs in man which can be attributed to dietary deficiencies in biotin or pantothenic acid. 

Vitamin B2, or riboflavin, is the metabolic precursor to two flavin coenzymes essential for the integrity of a spectrum of redox reactions. 

A rich source of iron and vitamins C and A, parsley also yields fatty acids and an essential or volatile oil. The essential oil of the leaves is considered superior to that from the seeds and is used in condiments and seasonings. Parsley seed oil is used in fragrances for perfumes, soaps and creams. Parsley has a very high content of vitamins (/i-carotene, thiamin, riboflavin and vitamins C and E) and is a rich source of calcium, iron and folate (Athar et al., 1999). A high proportion of the carotene is 9-cis-P-carotene, which is considered effective against cancer and cardiovascular disease (Ben-Amotz and Fishier, 1998). 

On the other hand, milk is not only an essential food for infants, but for children and adults as well. Children need sufficient nutrients and energy to meet the demands of growth and development. Demands for nutrients such as protein, Ca, Fe, and Zn are relatively high, and teenagers require quite large amounts of B vitamins - thiamine, riboflavin and niacin. In addition, approximately 45 percent of the adult skeleton is laid down during adolescence. 

---