Water-soluble vitamins ascorbic acid

Ascorbic acid commonly known as vitamin C, is one of the most important water soluble vitamins. Ascorbic acid is involved in many biological processes and it is an essential compound in the human diet [1]. The determination of ascorbic acid has gained increase significance in pharmaceutic, clinical, and food applications. So far, different methods have been developed for determination of ascorbic acid [2, 3]. 

Table 8.9 lists the water-soluble vitamins —ascorbic acid (vitamin C) and a series known as the vitamin B complex (Figure 8.32). Ascorbate, the ionized form of ascorbic acid, serves as a reducing agent (an antioxidant), as will be discussed shortly. The vitamin B series comprises components of coenzymes. Note that, in all cases except vitamin C, the vitamin must be modified before it can serve its function. 

In a wonderfully short and effective separation, seven water-soluble vitamins (ascorbic acid, niacin, niacinamide, pyridoxine, folic acid, thiamine, riboflavin) were baseline resolved on a Cg column using an isocratic 7/93 acetonitrile/water (1% acetic acid and 5mM sodium heptanesulfonate) mobile phase [1114]. Elution was complete in 6 min. 

The antiscurvy (antiscorbutic) activity was called vitamin C, and when its structure became known it was called ascorbic acid. The fat-soluble factor preventing rickets was designated vitamin D. By 1922, it was recognized that another fat-soluble factor, vitamin E, is essential for full-term pregnancy in the rat. In the early 1930s vitamin K and the essential fatty acids were added to the list of fat-soluble vitamins. Study of the human blood disorders "tropical macrocytic anemia" and "pernicious anemia" led to recognition of two more water-soluble vitamins, folic acid and vitamin B12. The latter is required in minute amounts and was not isolated until 1948. Have all the vitamins been discovered Rats can be reared on an almost completely synthetic diet. However, there is the possibility that for good health humans require some as yet undiscovered compounds in our diet. Furthermore, it is quite likely that we receive some essential nutrients that we cannot synthesize from bacteria in our intestinal tracts. An example may be the pyrroloquinoline quinone (PQQ).e... 

The antioxidants studied can be classified into two broad types phenolic antioxidants and non-phenolic antioxidants. Phenolic antioxidants have been found to be more promising as they are obtained from dietary sources.Vitamin E (a-tocopherol), the first known chainbreaking antioxidant, is also an o-methoxy phenol. Pulse radiolysis studies of vitamin E and its water-soluble analogue, trolox C, have been reported several years ago. a-tocopherol reacts with almost all the oxidizing free radicals, and the phenoxyl radicals produced during oxidation reactions absorb at -460 nm (Fig. 1). The regeneration reaction of a-tocopherol phenoxyl radicals back to a-tocopherol by water-soluble antioxidant ascorbic acid was also first reported by pulse radiolysis method. The one-electron reduction potential of vitamin E is -0.48 V vs. NHE. Both a-tocopherol and trolox C are used as standards for evaluating the antioxidant ability of new compounds. 

Of the water-soluble vitamins, intakes of nicotinic acid [59-67-6] on the order of 10 to 30 times the recommended daily allowance (RE)A) have been shown to cause flushing, headache, nausea, and moderate lowering of semm cholesterol with concurrent increases in semm glucose. Toxic levels of foHc acid [59-30-3] are ca 20 mg/d in infants, and probably approach 400 mg/d in adults. The body seems able to tolerate very large intakes of ascorbic acid [50-81-7] (vitamin C) without iH effect, but levels in excess of 9 g/d have been reported to cause increases in urinary oxaHc acid excretion. Urinary and blood uric acid also rise as a result of high intakes of ascorbic acid, and these factors may increase the tendency for formation of kidney or bladder stones. AH other water-soluble vitamins possess an even wider margin of safety and present no practical problem (82). 

Water-soluble vitamins removed by hemodialysis (HD) contribute to malnutrition and vitamin deficiency syndromes. Patients receiving HD often require replacement of water-soluble vitamins to prevent adverse effects. The vitamins that may require replacement are ascorbic acid, thiamine, biotin, folic acid, riboflavin, and pyridoxine. Patients receiving HD should receive a multivitamin B complex with vitamin C supplement, but should not take supplements that include fat-soluble vitamins, such as vitamins A, E, or K, which can accumulate in patients with renal failure. 

In an investigation of the water-soluble vitamins in human skin,71 it was found that 15 individuals showed relatively small ranges (less than 2-fold) for vitamin B12, folic acid, and biotin about 2-fold ranges in the cases of riboflavin, niacin, and thiamine about a 4-fold range in the case of ascorbic acid, and more than a 5-fold range in the case of pantothenic acid. In another study72 it was found that the total choline content of normal skin varied in four individuals over approximately a 10-fold range 127 to 1200 ig. per gm. The variation in the free choline in the same individuals was relatively small. 

The SP procedure of water-soluble vitamins from multivitamin tablets is particularly challenging due to the diverse analytes of varied hydrophobicities and pfC. Water-soluble vitamins (WSVs) include ascorbic acid (vitamin C), niacin, niacinamide, pyridoxine (vitamin B ), thiamine (vitamin Bj), folic acid, riboflavin (vitamin B2) and others. While most WSVs are highly water soluble, riboflavin is quite hydrophobic and insoluble in water. Folic acid is acidic while pyridoxine and thiamine are basic. In addition, ascorbic acid is light sensitive and easily oxidized. The extraction strategy employed was a two-step approach using mixed solvents of different polarity and acidity as follows ... 

Water-soluble vitamins in formulations have been determined by use of ion-pair chromatography. The vitamins include several B vitamins as well as niacin, folic acid, and ascorbic acid (565). Vitamins D and Da were rapidly separated on reverse phase columns (247) as are vitamins A, D, and E in multivitamin tablets (564). Addition of silver ions to the mobile phase has been shown to increase the flexibility inherent in RPC by complexing with the unsaturated bonds and thereby decreasing the retention factor. This effect is also observed with other unsaturated drug molecules including steroids (247). Vitamin A and related compounds have... 

Fig. 3 Electropherogram of five water-soluble vitamines thiamine (cationic), nicotinamide (nonionic), biotin (anionic), ascorbic acid (anionic), and nicotinic acid (anionic) in 20 mM phosphate run buffer at pH 8.0.

At low and medium doses, it is well established that the nutritional value of proteins, carbohydrates, and fats as macronutrients are not significantly impaired by irradiation, and neither the mineral bioavailability is impacted. Like all other energy depositing process, the application of ionizing radiation treatment can reduce the levels of certain sensitive vitamins. Nutrient loss can be minimized by irradiating food in a cold or frozen state and under reduced levels of oxygen. Thiamin and ascorbic acid are the most radiation sensitive, water-soluble vitamins, whereas the most sensitive, fat-soluble vitamin is vitamin E. In chilled pork cuts at the 3 kGy maximum at 0-10°C, one may expect about 35 0% loss of thiamin in frozen, uncooked pork meat irradiated at a 7 kGy maximum at —20°C approx., 35 % loss of it can be expected [122]. 

Vitamins are chemically unrelated organic compounds that cannot be synthesized by humans and, therefore, must must be supplied by the diet. Nine vitamins (folic acid, cobalamin, ascorbic acid, pyridoxine, thiamine, niacin, riboflavin, biotin, and pantothenic acid) are classified as water-soluble, whereas four vitamins (vitamins A, D, K, and E) are termed fat-soluble (Figure 28.1). Vitamins are required to perform specific cellular functions, for example, many of the water-soluble vitamins are precursors of coenzymes for the enzymes of intermediary metabolism. In contrast to the water-soluble vitamins, only one fat soluble vitamin (vitamin K) has a coenzyme function. These vitamins are released, absorbed, and transported with the fat of the diet. They are not readily excreted in the urine, and significant quantities are stored in Die liver and adipose tissue. In fact, consumption of vitamins A and D in exoess of the recommended dietary allowances can lead to accumulation of toxic quantities of these compounds. 

Nutritionally, the most important water-soluble vitamins in citrus fruits are ascorbic acid, folic acid and pyridoxine. Clinical studies on the bioavailability of these vitamins, as well as basic research on the absorption and chemistry of these vitamins, have yielded valuable information adding to our overall understanding of the nutritional quality and bioavailability of these vitamins found in citrus fruits. 

Ascorbic acid as a water-soluble vitamin (vitamin C) is an essential component in the human diet. As one of many anti-oxidants (vitamin E and 3-carotene are examples of fat-soluble anti-oxidants), ascorbic acid is required for the growth and repair of tissues in all parts of the body. It is necessary to form collagen, an important protein used to make skin, scar tissue, tendons, ligaments, and blood vessels. 

The fat-soluble vitamins are A, D, E, and K. The water-soluble vitamins are thiamine (vitamin Bj), riboflavin, nicotinic acid (niacin) and nicotinamide, pyridoxine (vitamin B6), pantothenic acid, biotin, para-aminobenzoic acid, choline, inositol, and other lipotropic agents, ascorbic acid (vitamin C), the riboflavonoids, folate, and vitamin B12 (see Figure 66.1 and Figure 66.2, and Table 66.1). 

Ascorbic acid (vitamin C) is a water-soluble vitamin but is not part of the B group. It is a metabolic requirement for all species but is a dietary requirement only for those that lack the enzyme for its synthesis (primates, guinea pigs, certain birds, fish). Therefore, it is not required in poultry diets. It is involved in the formation and maintenance of intercellular tissues having collagen or related substances as basal constituents. 

Water-soluble vitamins and co-factors also appear to elicit an effect on xenobiotic metabolism. Ascorbic acid has been shown to inhibit chemically induced chemical carcinogenesis in test systems (Shamberger, ( ). When diets are deficient in choline, the animals appear to become much more susceptible to chemically-... 

Many cells require media supplemented with complex B vitamins, while other vitamins are presumably supplied by the addition of serum to culture media. Nevertheless, when serum-free media are employed, not only the water-soluble vitamins should be provided, but also the lipid-soluble ones, such as biotin, folic acid, niacin, panthotenic acid, thiamine, and ascorbic acid, as well as the vitamins B12, A, D, E, and K. 

The water soluble vitamins, B2(riboflavin), Biascorbic acid) provided a very interesting study. The spectra for B12 and some of its analogs were first reported by Williams et al., [58] and consist of very strong Cotton bands across almost the entire visible spectral range, Figure 3. 

Vitamin C (or ascorbic acid) is a water-soluble vitamin containing a five-membered lactone that we first discussed in Section 3.5B. Although vitamin C is synthesized in plants, humans do not have the necessaiy enzymes to make it, and so they must obtain it from then-diet. 

Among the water-soluble vitamins subject to photodegradation during administration, thiamine, ascorbic acid, and riboflavine must be considered. A multivitamin product containing all of these vitamins was added to both 0.9% NaCl and 5% dextrose infusion solutions packaged in PVC and Clearflex containers. These admixtures were then exposed to photonic energy (2000 lux) for 24 hours and showed a rapid degradation of both riboflavine and ascorbic acid (95). 

Ascorbic acid. Vitamin C, is a water-soluble vitamin of great im-portance. A deficiency of vitamin C in the diet leads to scurvy, a disease characterized by loss of weight, general weakness, hemorrhagic condition of the gums and skin, loosening of the teeth, and other symp-toms. Sound tooth development seems to depend upon a satisfactory supply of this vitamin, and a deficiency is thought to cause a tendency to incidence of a number of diseases. 

Vitamins are classified into two categories Fat-soluble Vitamins (A, D, E, K) and Water-soluble Vitamins (All B, Biotin, Folic acid and Ascorbic acid). 

Some itamirLS are water soluble, while others are fat soluble. This classification is valuable as it indicates whether the vitamin is likely to be absorbed similarly to lipids or like other water-soluble nutrients. The fat-soluble vitamins are A, D, E, and K. The water-soluble vitamins arc ascorbic acid, biotin, folate, niacin, pantothenic acid, riboflavin, thiamin, vitamin B i, and vitamin B 2. The classification is also valuable, as it helps chemists decide on the best way to extract and analyze a particular vitamin in foods and biological tissues. Aside from having some bearing on the path ways of absorption and distribution throughout the body, the question of whether a particular vitamin is fat soluble or water soluble has little or no relevance to its function in the body. 

Ascorbic acid, also known as vitamin C, is a water-soluble vitamin. The KDA for the adult is 60 mg. Good sources of ascorbic acid are bell peppers, broccoli, citrus fruit, spinach, tomatoes, and potatoes. Animal products contain some vitamin C while grains contain essentially none. 

The potential of PBI LC-MS in the analysis of various vitamins was explored by Careri et al. [99-100]. The fat-soluble vitamins A, D, and E were analysed in food and multivitamin preparations [99]. Absolute detection limits in SIM mode were 0.6-25 ng after fast leversed-phase separation using a 97% aqueous methanol as mobile phase. Mass spectra in El, positive-ion and negative-ion Cl were obtained and discussed. The mass-spectral and quantitative performance of PBI LC-MS in the analysis of eleven water-soluble vitamins was also explored [100]. Detection limits were determined in SIM mode under positive-ion Cl, and were below 15 ng for ascorbic acid, nicotinamide, nicotinic acid, and pyridoxal, around 100 ng for dehydroascorbic acid, panthothenic acid, and thiamine, and above 200 ng for biotin, pyridoxamime, and pyridoxine. Riboflavine was not detected. 

Although the water-soluble vitamins are structurally diverse, they are put in a general class to distinguish them from the lipid-soluble vitamins. This cla.ss includes the B-complex vitamins and ascorbic acid (vitamin C). The term B-complex vitamins usually refers to thiamine, riboflavin, pyridoxine. nicotinic acid, pantothenic acid, hiotin. cyanocobalamin. and folic acid. Dietary deficiencies of any of the B vitamins commonly are complicated by deftciencies of another mem-ber(s) of the group,. so treatment with B-complex preparations is usually indicated. 

Disposable transport-facilitating moieties are also used to enhance the absorption of the water-soluble vitamins used as food additives, such as thiamine, ascorbic acid, and riboflavine. The vitamin derivatives obtained are poorly water-soluble and therefore are less extracted during the preparation of the food, which also gives some protection against oxidative decomposition. The increased lipophilicity enhances absorption from the intestinal tract (Fig. 32)151 155>. 

Fig. 8-87. Analysis of water-soluble vitamins. - Separator column Spherisorb ODS 2 (5 pm) eluent (A) 0.1 mol/L KOAc (pH 4.2 with HOAc), (B) water/methanol/acetonitrile (50 10 40 v/v/v) gradient linear, 6% B in 30 min to 100% B flow rate 2 mL/min detection UV (254 nm) injection volume 50 pL solute concentrations 5 nmol each of ascorbic acid (1), nicotinic acid (2), thiamine (3), pyridoxine (4), nicotinic add amide (5), p-aminobenzoic add (6), cyanocobala-mine (7), and riboflavine (8).

The answer is e. (Murray, pp 627-661. Sciiver, pp 3897-3964. Sack, pp 121-138. Wilson, pp 287-320.) Ascorbic acid (vitamin C) is found in fresh fruits and vegetables. Deficiency of ascorbic acid produces scurvy, the sailor s disease. Ascorbic acid is necessary for the hydroxylation of proline to hydroxyproline in collagen, a process required in the formation and maintenance of connective tissue. The failure of mesenchymal cells to form collagen causes the skeletal, dental, and connective tissue deterioration seen in scurvy. Thiamine, niacin, cobalamin, and pantothenic acid can all be obtained from fish or meat products. The nomenclature of vitamins began by classifying fat-soluble vitamins as A (followed by subsequent letters of the alphabet such as D, E, and K) and water-soluble vitamins as B. Components of the B vitamin fraction were then given subscripts, e.g., thiamine (Bi), riboflavin (B2), niacin [nicotinic acid (B3)], panthothenic acid (B5), pyridoxine (Bg), and cobalamin (B ). The water-soluble vitamins C, biotin, and folic acid do not follow the B nomenclature. 

Vitamin C (ascorbic acid, Fig. 2) is a water-soluble vitamin that dissociates at physiological pH. It is essential as a cofactor of several enzymes, including proline hydroxylase and lysine hydroxylase. Scurvy is known as the result of malnutrition with ascorbic acid. This vitamin deficiency is characterized by instable collagen. This results from insufficient hydroxylation of collagen molecules. Besides this, ascorbic acid has a function as an antioxidant. 

---