Ascorbic acid vitamin toxicity

As with all methods, this approach has some limitations it uses acetonitrile, which is toxic, and the separation of glucose from fructose can sometimes be problematic after extended use of the column. However, sample preparation is easy since it requires only dilution to the required level (often 1 10) and filtration prior to analysis to remove particulate materials, which protects and extends the useful life of the column. The degradation of the resolution between glucose and fructose is caused by the partial inactivation of the column by materials in the matrix, but this resolution can be recovered by reducing the acetonitrile concentration in the solvent. The same column can also be used to assay the level of ascorbic acid (vitamin C) in a soft drink or fruit juice, although different detection and solvent systems are used. 

The inhibition of the enzyme tyrosinase may very well be a key to the control of melanoma, and some of the known inhibitors include eommon substances. Thus, vitamin C, among other common and uncommon substances, has been listed as an enzyme inhibitor for tyrosinase in M.K. Jain s Handbook of Enzyme Inhibitors, 1965-1977 (1982). In addition to ascorbic acid (vitamin C), these other substances include the following halide ion (e.g., from the chloride of common salt, or from iodides and fluorides) butyric acid (from rancid butter) lactic acid (the end product of cancer cell metabolism, found naturally in sour milk products) oxalic acid (ordinarily considered toxic, although it occurs naturally in rhubarb and wood sorrel, etc.) formic acid (a component of ant stings) tyrosine itself and deadly cyanide (which is a chemically bound component of laetrile), as found in almonds (notably bitter almonds), in apricot seeds, and in certain legumes such as beans, etc., although the heat from cooking may drive off the cyanide content. 

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). 

The selection of an appropriate antioxidant depends on factors such as stability, toxicity, efficiency, odor, taste, compatibility with other ingredients, and distribution phenomena between the two phases. Antioxidants that give protection primarily in the aqueous phase include sodium metabisulfite, ascorbic acid, thioglycerol, and cysteine hydrochloride. Oil-soluble antioxidants include lecithin, propyl gal-late, ascorbyl palmitate, and butylated hydroxytoluene. Vitamin E has also been used, but its virtue as a natural antioxidant has been the subject of some controversy. 

Antioxidants Reducing agents, such as vitamins C (ascorbic acid) and E (a-tocopherol), which scavenge toxic free radicals generated by oxidative reactions in the cell. 

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. 

Vitamin C (ascorbic acid) functions as an antioxidant and as a cofactor for hydroxyla tion reactions in procollagen. A deficiency of vitamin C results in scurvy, a disease char acterized by sore, spongy gums, loose teeth, and poor wound healing. There is no known toxicity for this vitamin. 

Plants are significant to the diet of humans and animals since they provide most of the essential nutrients and vitamins. Vitamins C (ascorbic acid), E (a-tocopherol) and K (phylloquinone) are biosynthesized by plants, while (3-carotene, the precursor of vitamin A and ergosterol, the precursor of vitamin D, are also secondary plant metabolites. These metabolites are used in folk medicine and for industrial purposes, as raw materials for pharmaceutical and other products [3]. On the other hand, plants may produce substances, which are toxic and/or irritant to man. 

Vitamin C is also able to protect the hypothalamus from oxidative stress induced in rats by an environmental toxicant (Muthuvel et al., 2006). Ascorbic acid confers protection from increased free-radical activity in the brain of spontaneously hypertensive rats by improving total antioxidant and superoxide dismutase status, thus preventing high blood pressure and its complications (Newaz et al., 2005). Also, intravenous cerebroprotective doses of citrate/sorbitol-stabilized DHA are correlated with increased brain ascorbate levels and a suppression of excessive lipid peroxidation (Mack et al., 2006). 

Nothing is inherently wrong with what man manufactures its goodness or badness depends merely on what use we make of it. There is nothing bad about vitamin C just because it is manufactured it is still ascorbic acid (or one of its salts) and is just as effective as any other kind. So let us get rid of this myth about synthetic . At every opportunity, we should explain patiently why it is nonsensical to equate synthetic with toxic . 

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