Vitamin water-insoluble

The solubility (or insolubility) of different vitamins is of concern in nutrition. Molecules of vitamins B and C contain several —OH groups that can form hydrogen bonds with water (Figure 10.3). As a result, they are water-soluble, readily excreted by the body, and must be consumed daily. In contrast, vitamins A, D, E, and K, whose molecules are relatively nonpolar, are water-insoluble. These vitamins are not so readily excreted they tend to stay behind in fatty tissues. This means that the body can draw on its reservoir of vitamins A, D, E, and K to deal with sporadic deficiencies. Conversely, megadoses of these vitamins can lead to very high, possibly toxic, concentrations in the body. 

Molecular structures of vitamin 02 and vitamin B(. Polar groups are shown in color. Vitamin D2 is water-insoluble and vitemin Be is water-soluble. 

Nutrient analysis of stabilized rice bran and its derivatives indicates that it is a good source of protein, dietary fiber and carbohydrates, in addition to several valuable phytonutrients, antioxidants, vitamins and minerals (Table 17.1). SRB and its water-soluble and water-insoluble derivatives contain all the nutrients at different levels. They are gluten and lactose free and do not give rise to any food allergy. 

A surfactant is a surface-active agent that is used to disperse a water-insoluble drug as a colloidal dispersion. Surfactants are used for wetting and to prevent crystal growth in a suspension. Surfactants are used quite extensively in parenteral suspensions for wetting powders and to provide acceptable syringability. They are also used in emulsions and for solubilizing steroids and fat-soluble vitamins. 

Another application is the esterification of menahydroquinone-4, a water-insoluble vitamin K, with V,A-dimethylglycine [144], The 1-mono, 4-mono, and 1,4-bis esters were found to be water-soluble and rapidly hydrolyzable by liver and plasma esterases. A rapid pharmacodynamic response was seen after intravenous administration of the prodrugs. 

Both water-soluble and water-insoluble vitamins can be toxic in large quantities. Our bodies are much more tolerant of the water-soluble ones, however. Why ... 

In pinocytosis, the transport of water-insoluble substances such as vitamins A, D, E, and K is accomplished in the following manner. First, they are engulfed by the membranes, after which they are dissolved in the membranes and released unchanged in the inside compartment. 

FIGURE 1.4 A mechanism for transport of water-insoluble vitamins. 

Of these possibilities only a few can be used where CD is the detector. Sterols, sterones and water insoluble vitamins e.g. vitamin D2 and D3 have been investigated by colour induction [28]. Purdie et al. have successfully applied these selective CD methods in the chemical analysis e.g. by the determination of serum... 

The major benefit of the solubilization principle is the increased water solubility of water-insoluble drugs such as phenolic compounds, iodine, steroids, and vitamins. The solubilization of water-insoluble materials in micelles may have some effects on drug activity and absorption. In addition, drugs in the micelles may prefer to stay... 

Vitamin A contains 20 carbons and a single OH group, making it water insoluble. Because it is organic, it is soluble in any organic medium. To understand the consequences of these solubility characteristics, we must learn about the chemical environment of the body. 

Sesame oil, cottonseed oil, and other vegetable oils are used as vehicles for water-insoluble drugs such as corticosteroids and oil-soluble vitamins. Oily solutions can be administered only by intramuscular injection. 

The micelle-forming molecule TPGS is an effective vehicle for lipid-based drug delivery, and is also a water-soluble source of the water-insoluble oil Vitamin [16] jjjY protease inhibitor, amprenavir,... 

The water-insoluble solvents used in commercially available solubilized oral formulations include oleic acid, DL-a-tocopherol (Vitamin E), the long-chain triglycerides peanut oil, corn oil, soybean oil, sesame oil, olive oil, peppermint oil, and castor oil, the medium-chain triglycerides derived from coconut oil and palm seed oil, and the short-chain triglyceride triacetin. 

Propylene glycol esters of fatty acids such as propylene glycol laurate and propylene glycol monolaurate can be used alone or as a cosurfactant. Menatetrenone (also known as vitamin K2) is used in the treatment of osteoporosis and is practically water insoluble and formulated as a solution in propylene glycol esters of fatty acids and glyceryl monooleate as 15 mg Glakay soft gelatin capsules. 

Ritonavir, an HIV protease inhibitor with peptidelike structure, has an intrinsic water solubility of l.Opg/ml. Norvir is a thermodynamically stable solution formulation containing 100 mg of ritonavir dissolved in a mixture of oleic acid, Cremophor EL, ethanol, and the antioxidant butylated hydroxytoluene (BHT), and filled into soft gelatin capsules. However, Norvir is being replaced by Kaletra oral solution and soft gelatin capsule, which is a combination of 133.3 mg of lopinavir and 33.3 mg ritonavir dissolved in a mixture of oleic acid, polyoxyl 35 castor oil (Cremophor EL), and propylene glycol. The water-insoluble HIV protease inhibitor, saquinavir, is solubilized by a mixture of Vitamin E and medium-chain mono- and diglycerides in 200 mg Fortovase soft gelatin capsules. 

Macrogol 15 hydroxystearate is used in parenteral pharmaceutical preparations in concentrations up to 50% to solubilize diclofenac, propanidid, and vitamin Kl. It has also been used in preclinical formulations in preparing supersaturated injectable formulations of water-insoluble molecules. It is generally regarded as a relatively nontoxic and nonirritant excipient. 

The polysorbate nonionics have also been employed in the preparation of aqueous injections of the water-insoluble vitamins A, D, E and K. Table 6.14 shows the solubility of these vitamins in 10% polysorbate solutions, polysorbate 20 and 80 being the best two solubilisers. 

Liquid-liquid extraction is generally reserved for more complex samples because it offers poorer precision than other techniques. It is most commonly used for the preparation of biological samples in which less precise methods can be tolerated. Occasionally, however, an extraction is necessary for the determination of a water-insoluble compound in a water-soluble matrix, such as the analysis of fat-soluble vitamins in tablets or menthol in pharmaceutical lozenges. In these cases, the water-soluble matrix must be treated with water to gain access to the analytes, but the solvent cannot be made sufficiently nonpolar to dissolve the analytes by adding a water-miscible solvent. 

The bile-salt-dependent lipase of pancreatic juice has many names such as cholesterol esterase, nonspecific lipase, the most rational being carboxyl ester lipase [27], In the case of water-insoluble substrates this enzyme has an absolute requirement for bile salts specifically having hydroxyl groups in the 3a and la positions [28.29]. The best documented role for this enzyme is to allow the absorption of dietary cholesterol, through hydrolysis of cholesterol esters in the lumen. The enzyme also catalyzes the esterification of cholesterol and a role for it has been proposed in cholesterol absorption [30]. In addition, a wide range of primary and secondary fatty acyl esters including glycerides, vitamin A and E esters are hydrolyzed by this enzyme. 

Two examples of radical inhibitors that are present in biological systems are vitamin C and vitamin E. Like hydroquinone, they form relatively stable radicals. Vitamin C (also called ascorbic acid) is a water-soluble compound that traps radicals formed in the aqueous environment of the cell and in blood plasma. Vitamin E (also called a-tocopherol) is a water-insoluble (hence fat-soluble) compound that traps radicals formed in nonpolar membranes. Why one vitamin functions in aqueous environments and the other in nonaqueous environments should be apparent from their structures and electrostatic potential maps, which show that vitamin C is a relatively polar compound, whereas vitamin E is nonpolar. 

Early nutritional studies divided vitamins into two classes water-soluble vitamins and water-insoluble vitamins (Table 25.1). Vitamins A, D, E, and K are water insoluble. Vitamin K is the only water-insoluble vitamin currently known to function as a coenzyme. Vitamin A is required for proper vision, vitamin D regulates calcium and phosphate metabolism, and vitamin E is an antioxidant. Because they do not function as coenzymes, vitamins A, D, and E are not discussed in this chapter. Vitamins A and E are discussed in Sections 9.8 and 26.7, and vitamin D is discussed in Section 29.6. 

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