Vitamin ergocalciferol

Fat-Soluble Retinol (vitamin A) Ergocalciferol (vitamin Dg) Cholecalciferol (vitamin Dg) n-Tocopherol (vitamin E) Vitamin K ... 

Vitamin D is often combined in varying amounts with calcium salts. A multiple vitamin is another good source of vitamin D. Most multivitamins contain 400 IU per tablet. Vitamin D is also available as a single entity. Doses above 2000 IU/day should be avoided owing to the risk of hypercalciuria and hypercalcemia. Ergocalciferol (vitamin D2) and... 

The active vitamins are produced by conversion of provitamins by ultraviolet light. Ergosterol, a yeast sterol, is converted to its active form, ergocalciferol (vitamin D2), and 7-dehydrocholesterol, which is found in many natural foods and is also synthesized in man, is converted to cholecalciferol (vitamin D3). Fish liver oils are virtually the only source of vitamin D3 in nature. The most active form of vitamin D3 is 1,25-dihydroxycholecalciferol and this is produced by the hydroxylation of cholecalciferol at position 25 in the liver and then at position 1 in the kidney. 

Vitamin D is commonly found in two forms, both derivatives of steroids. These are known as cholecalciferol (vitamin D3) and ergocalciferol (vitamin D2). Cholecalciferol is formed directly from the steroid known as 7-dehydrocholesterol by the action of sunlight, or other source of ultraviolet (UV) light, in the skin of humans and other animals. When parents encourage their children to go out and play in the sun, there is good reason for doing so (but avoid sunburn). ... 

In addition to the endogenous metabolites, some exogenous sterols possess biological activity similar to that of D3. Ergocalciferol (vitamin D2) is derived from the plant sterol ergosterol and may act as a substrate for both the 25-hydroxylase and the 1-hydroxylase enzyme systems of the liver and kidney to form 25-(OH)D2 and 1,25-(0H)2 D2, respectively. Ergocalciferol (vitamin D2) is the form used in commercial vitamins and supplemented dairy products. Dihydrotachysterol, another sterol that is used as a therapeutic agent, also functions as a substrate for the hydroxylase enzymes in the liver and kidney. 

Cholecalciferol is pure vitamin D3 derived from the ultraviolet conversion of 7-dehydrocholesterol to cholecalciferol. Ergocalciferol vitamin D2) is a sterol derived from yeast and fungal ergosterol. Calcitriol [Rocaltrol, 1,25-(0H)2D3] is the metabolically active vitamin D3 compound. Dihydrotachysterol is a synthetic compound that may act somewhat more quickly than either vitamin D2 or D3. 

Using the Woodward-Fieser rules, we can predict the absorption maximum of an unsaturated compound with pleasing accuracy, generally to within 5 nm of the observed value. For example, the calculated absorbance maximum of ergocalciferol (vitamin D2) of 265 nm (Figure 2.8) is only 1 nm different from the observed value at 266 nm (Figure 2.9). 

Figure 2.8 Ergocalciferol (vitamin D2) and the calculated absorption maximum...

Diet Ergocalciferol (vitamin D2), found in plants, and cholecalc-iferol (vitamin 03), found in animal tissues, are sources of preformed vitamin D activity (Figure 28.22). Ergocalciferol and cholecalciferol differ chemically only in the presence of an additional double bond and methyl group in the plant sterol. 

However, it was not until 1924, when Steenbock and Hess showed that irradiation of certain foods generated protective activity against the disease, that vitamin D (calciferol) was recognized as a second lipid-soluble vitamin. Vitamin D is a family of compounds formed by the irradiation of A5/7-unsaturated sterols such as ergosterol and 7-dehydrocholesterol. The former yields ergocalciferol (vitamin D2) and the latter cholecalciferol (vitamin D3). 

Vitamin D is represented by cholecalciferol (vitamin D3) and ergocalciferol (vitamin D2), which are structurally similar secosteroids derived from the UV irradiation of provitamin D sterols. In vertebrates, vitamin D3 is produced in vivo by the action of sunlight on 7-dehydrocholesterol in the skin. Vitamin D2 is produced in plants, fungi, and yeasts by the irradiation of ergosterol. On irradiation, the provitamins are converted to previtamin D, which undergoes thermal transformation to vitamin D. 

Vitamin B. (.W pyridoxine) Vitamin B See cyanocobalamin) Vitamin C (See ascorbic acid) Vitamin D (Ergocalciferol) Vitamin D5 (Chlolcalciferol)... 

H N.m.r. spectra, with use of the shift reagent [Eu(dpm)3], indicate that ring A of ergocalciferol (vitamin D2) exists as a 1 1 mixture of chair conformers in solution, with the OH conformation equatorial and axial, respectively.8 la-Hydroxy-3-epi-vitamin D3 (la,3a-diol) exists in CDC13 solution as a 4 1 mixture of the 1,3-diaxial and 1,3-diequatorial conformers.9... 

Plants contain the steroid ergosterol. Ergosterol is a provitamin of vitamin D. Exposure of ergosterol to ultraviolet light results in its conversion to ergocalciferol (vitamin D2). Farmers, for example, leave their hay out in the sun to dry. This process results in the conversion of ergosterol to vitamin D2- Cows benefit from the increased levels of vitamin Dj produced in their feed. 

Ergocalciferol (vitamin D2) is produced in plants from ergosterol on UV irradiation. Vitamin D2 is the form most often used in commercial products and to fortify foods. Although different in structure, its biological activity is comparable to that of vitamin and mu.st be bioactivated in a similar fa.shion. 

Ergocalciferol (vitamin D2) is formed by irradiation of ergosterol, a plant sterol common in the diet. It differs from cholecalciferol in the side chain attached to the D ring (Figure 37-1). Irradiation of ergosterol is an important commercial method for the synthesis of vitamin D2, which is used for enriching cow s milk. The practice... 

L. T. Grady and K. D. Thakker, Stability of solid drugs Degradation of ergocalciferol (vitamin D2) and cholecalciferol (vitamin D3) at high humidities and elevated temperatures, J. Pharm. Sci. 69, 1099-1102 (1980). 

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