Vitamins compounds

T During the first third of the twentieth century, a major focus of research in physiological chemistry was the identification of vitamins, compounds that are essential to the health of humans and other vertebrates but cannot be synthesized by these animals and must therefore be obtained in the diet. Early nutritional... 

Zitmane, I., [Data on biochemical investigation of protein-vitamin compound derived from topinambour II], Latvijas PSR Zinatnu Akademijas Vestis, 10, 83-87, 1958. 

Similarly, streptavidin from Streptomyces avidinii - and also its eukaryotic counterpart avidin, which occurs in chicken egg white - has evolved only in order to tightly complex biotin, a small vitamin compound [15]. In this case the complexation is kinetically almost irreversible, which makes sense for its role as a bacterial antibiotic protein and has led to its widespread use as a biochemical reagent (for references, see [16]). 

Model vitamin compounds (a) a Schiff base derivative, and (b) a cobal-oxime, in this case derived from dimethylglyoxime. 

Since trimethylbenzoquinone is not converted into 2 , it appears that the complete side chain of a-tocopherol is not removed before building up the Cso side chain. In this respect, the biosynthesis of 2 differs from that of vitamin K2 The possible biochemical significance of 2 , which we can also think of as deoxyubiquinone, in the mitochondrial respiratory chain remains to be investigated. It would obviously be of great interest if this new compound is found to be present in mitochondria. Ubiquinone and tocopherol are present, but tocopherylquinonc is not. If the new vitamin compound were found in mitochondria, it would clearly support those who would ascribe to vitamin some specific function in respiratory-enzyme systems. This possibility has existed ever since the... 

Different infant formula, rice flour and wheat powder conunercial samples were tested using the developed method. The results demonstrated that the proposed method is both sensitive and selective enough to be applied for the fast determination of these compounds at a wide range of concentration levels in real samples. Vitamin C was not detected from aU the samples. The values for riboflavin and nicotinamide were 10 times higher than the value for cyanocobalamin. The vitamin compounds were also found at different low concentration-level ng/mL. 

Table 53. h.Rf-values of vitamin compounds in various separation systems... 

Gregory III JF, Hiner ME. Thermal stability of vitamin compounds in liquid model food... 

The matrix is brought into an extraction chamber which, in this case, is filled with CO2 gas and pressurized to about 8000 psi with simultaneous heating at 65°C for a few minutes (98,115,116). At these conditions CO2 is working as an apolar solvent which is able to extract highly lipophilic compounds. After this SFE process the exit valve is opened to bleed out the extract-laden CO2, and the extract is collected on silica gel by simultaneous evaporation of the CO2 gas. Without any further purification the vitamin compounds can be quantitated, as usual, on HPLC. If samples are introduced into a heated and density-programmed analytical silica column (coated with, e.g., cyanopropyl-methyl-polysiloxane) of 10 m length (15), instead of an extraction chamber, the compounds can be ex-... 

Kawamoto and coworkers used HPLC and post-column derivatization with 2,6-dibromoquinone-4-chlorimide to quantify PN in pharmaceutical products (88). The condensation product shows strong absorption in the visible spectrum (650 nm) detection has been reported to be almost seven times more sensitive than UV (250 nm) detection of PN. The main advantage of this method is selectivity other B vitamins or caffeine (often present in vitamin preparations) were shown not to interfere in PN quantiflcation. The disadvantage of the method is that two postcolumn reaction pumps with reaction coils are required to deliver reagents to the column eluate. Furthermore, only PN can be analyzed by this method, while most modem quality control programs tend to optimize vitamin analyses by simultaneous analysis of several vitamin compounds. 

It may be regarded as the parent of a number of important classes of compounds derived from the y-pyrone skeleton (e.g. flavone, xan-thone) and the important chroman derivatives called the tocopherols (vitamin E). 

Molecular distillation is used in the separation and purification of vitamins and other natural products, and for the distillation of high-boiling synthetic organic compounds. 

The related compounds pyridoxamine and pyridoxal, in which the CH2OH group in the 4-position is replaced by CH2NH2 and CHO respectively, also possess vitamin activity and for certain bacteria are much more active than pyridoxine. 

The term vitamin K2 was applied to 2-methyl-3-difarnesyl-l,4-naphthoquinone, m.p. 54 C, isolated from putrefied fish meal. It now includes a group of related natural compounds ( menaquinones ), differing in the number of isoprene units in the side chain and in their degree of unsaturation. These quinones also appear to be involved in the electron transport chain and oxidative phosphorylation. 

Cobalt compounds have been in use for centuries, notably as pigments ( cobalt blue ) in glass and porcelain (a double silicate of cobalt and potassium) the metal itself has been produced on an industrial scale only during the twentieth century. Cobalt is relatively uncommon but widely distributed it occurs biologically in vitamin B12 (a complex of cobalt(III) in which the cobalt is bonded octahedrally to nitrogen atoms and the carbon atom of a CN group). In its ores, it is usually in combination with sulphur or arsenic, and other metals, notably copper and silver, are often present. Extraction is carried out by a process essentially similar to that used for iron, but is complicate because of the need to remove arsenic and other metals. 

Corrin is the porphyrinoid chromophore of the vitamin parent compound cobyrinic acid. Corrin itself has not yet been synthesized, but routes to cobyrinic acid and several other synthetic corrins have been described by A. Eschenmoser (1970, 1974) and R.B. Woodward (1967). 

The thiazole ring can be found in numerous molecules that possess biological activity the thiamine (vitamin B,), penicillins, antiinflamatory and bactericidals compounds, and so forth. 

As noted by Robinson and Strachan (1), after considerable activity in the period 1885 to 1895 thiazolecarboxylic acids received little attention until 1935. Isolation of 4-methyl-5-thiazolecarboxylic acid after degradation of vitamin Bj gave new interest to the chemistry of these compounds. 

Firefly lucifenn is an example of an azole that contains a benzene ring fused to the five membered ring Such structures are fairly common Another example is benzimidazole present as a structural unit m vitamin B12 Some compounds related to benzimidazole include purine and its ammo substituted derivative adenine one of the so called het erocychc bases found m DNA and RNA (Chapter 28)... 

Naturally occurring compounds with carbon-metal bonds are very rare The best example of such an organometallic compound is coenzyme Bi2 which has a carbon-cobalt ct bond (Figure 14 4) Pernicious anemia results from a coenzyme B12 deficiency and can be treated by adding sources of cobalt to the diet One source of cobalt IS vitamin B12 a compound structurally related to but not identical with coen zyme B12... 

Vitamin D3 is a key compound m the process by which Ca " is absorbed from the mtes tine Low levels of vitamin D3 lead to Ca " concentrations m the body that are msuffi cient to support proper bone growth resulting m the bone disease called rickets... 

Many pharmaceutical compounds contain chromophores that make them suitable for analysis by UV/Vis absorption. Products that have been analyzed in this fashion include antibiotics, hormones, vitamins, and analgesics. One example of the use of UV absorption is in determining the purity of aspirin tablets, for which the active ingredient is acetylsalicylic acid. Salicylic acid, which is produced by the hydrolysis of acetylsalicylic acid, is an undesirable impurity in aspirin tablets, and should not be present at more than 0.01% w/w. Samples can be screened for unacceptable levels of salicylic acid by monitoring the absorbance at a wavelength of... 

The elution order for neutral species in MEKC depends on the extent to which they partition into the micelles. Hydrophilic neutrals are insoluble in the micelle s hydrophobic inner environment and elute as a single band as they would in CZE. Neutral solutes that are extremely hydrophobic are completely soluble in the micelle, eluting with the micelles as a single band. Those neutral species that exist in a partition equilibrium between the buffer solution and the micelles elute between the completely hydrophilic and completely hydrophobic neutrals. Those neutral species favoring the buffer solution elute before those favoring the micelles. Micellar electrokinetic chromatography has been used to separate a wide variety of samples, including mixtures of pharmaceutical compounds, vitamins, and explosives. 

Chloroacetate esters are usually made by removing water from a mixture of chloroacetic acid and the corresponding alcohol. Reaction of alcohol with chloroacetyl chloride is an anhydrous process which Hberates HCl. Chloroacetic acid will react with olefins in the presence of a catalyst to yield chloroacetate esters. Dichloroacetic and trichloroacetic acid esters are also known. These esters are usehil in synthesis. They are more reactive than the parent acids. Ethyl chloroacetate can be converted to sodium fluoroacetate by reaction with potassium fluoride (see Fluorine compounds, organic). Both methyl and ethyl chloroacetate are used as agricultural and pharmaceutical intermediates, specialty solvents, flavors, and fragrances. Methyl chloroacetate and P ionone undergo a Dar2ens reaction to form an intermediate in the synthesis of Vitamin A. Reaction of methyl chloroacetate with ammonia produces chloroacetamide [79-07-2] C2H ClNO (53). 

Other Uses. More than 70 thousand metric tons of acetone is used in smaU volume appHcations some of which are to make functional compounds such as antioxidants, herbicides, higher ketones, condensates with formaldehyde or diphenylamine, and vitamin intermediates. 

The FCC is to food-additive chemicals what the USP—NF is to dmgs. In fact, many chemicals that are used in dmgs also are food additives (qv) and thus may have monographs in both the USP—NF and in the FCC. Examples of food-additive chemicals are ascorbic acid [50-81-7] (see Vitamins), butylated hydroxytoluene [128-37-0] (BHT) (see Antioxidants), calcium chloride [10043-52-4] (see Calcium compounds), ethyl vanillin [121-32-4] (see Vanillin), ferrous fumarate [7705-12-6] and ferrous sulfate [7720-78-7] (see Iron compounds), niacin [59-67-6] sodium chloride [7647-14-5] sodium hydroxide [1310-73-2] (see lkaliand cm ORiNE products), sodium phosphate dibasic [7558-79-4] (see Phosphoric acids and phosphates), spearmint oil [8008-79-5] (see Oils, essential), tartaric acid [133-37-9] (see Hydroxy dicarboxylic acids), tragacanth [9000-65-1] (see Gums), and vitamin A [11103-57-4]. 

Sulfur Dioxide and Sulfites. Sulfur dioxide [7446-09-5], SO2, sodium bisulfite [15181-46-1], NaHSO, and sodium metabisulfite [23134-05-6] ate effective against molds, bacteria, and certain strains of yeast. The wine industry represents the largest user of sulfites, because the compounds do not affect the yeast needed for fermentation. Other appHcations include dehydrated fmits and vegetables, fmit juices, symps and concentrates, and fresh shrimp (79). Sulfites ate destmctive to thiamin, and cannot be used in foods, such as certain baked goods, that ate important sources of this vitamin. 

Reported cases of vitamin toxicity owing to overdose are usually associated with increased over-the-counter availabiHty of supplemental vitamins and indiscriminate supplementation. The misconception that if a Httle is good a lot is better has compounded toxicological problems with the vitamins. Eat-soluble vitamins tend to accumulate in the body with relatively inactive mechanism for excretion and cause greater toxicological difficulties than do water-soluble vitamins. 

---