Irradiation vitamins

Ohmae and Katsui irradiated vitamin K-l (82) in alcoholic solution with UV light and obtained the hydroperoxide (85), its corresponding hydroxide and the ketone (89). Also isolated were phthiocol (90), the naphthofuran (91) and polymeric material [69], Similar irradiation in benzene gave (89) and (91) [70],... 

Vitamin D is a secosteroid produced in the skin from 7-dehydrocholesterol under the influence of ultraviolet irradiation. Vitamin D is also found in certain foods and is used to supplement dairy products. Both the natural form (vitamin D3, cholecalciferol) and the plant-derived form (vitamin D2, ergocalciferol) are present in the diet. These forms differ in that ergocalciferol contains a double bond (C22-23) and an additional methyl group in the side chain (Figure 42-2). In humans this difference apparently is of little physiologic consequence, and the following comments apply equally well to both forms of vitamin D. 

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. 

Potassium ascorbate vitamin D source, enriched farina Yeast, dried irradiated vitamin D, pharmaceuticals Cod liver oil vitamin deriv., hair care Panthenyl triacetate vitamin deriv., lip care Panthenyl triacetate vitamin deriv., massage oils Panthenyl triacetate vitamin deriv., skin care Panthenyl triacetate vitamin deriv., skin care oils Panthenyl triacetate vitamin E precursor synthesis N-Methyl-2-pyrrolidone vitamin E source Wheat (Triticum vulgare) germ oil vitamin E source, food... 

Needles. + HjO from AoOEt-MeOH. M.p. l52-3°. [a] ) — 109 in CHCI3. Absorption spectrum and colour reactions similar to ergo-sterol.. Irradiation —> vitamin EL. 

Two published studies (Pugliese et al, 1985, 1986) showed the protective effect of vitamin E acetate on lipid peroxidation, which occurs after UV irradiation. Vitamin E acetate also reduces premature skin ageing caused by UV irradiation and it has been proved that a sufficiently high dose of vitamin E acetate has a positive effect in reducing erythema production after sunburn. 

Infants maybe sensitive to doses of vitamin A [11103-57-4] in the range of 75,000—200,000 lU (22.5—60 mg), although the toxic dose in adults is probably 2—5 million lU (90.6—1.5 g). Intakes in this range from normal food suppHes without oral supplements are simply beyond imagination (79). Vitamin D [1406-16-2] toxicity is much more difficult to substantiate clinically. Humans can synthesize active forms of the vitamin in the skin upon irradiation of 7-dehydrocholesterol. Toxic symptoms are relatively nonspecific, and dangerous doses seem to He in the range of 1000—3000 lU/kg body wt (25—75 flg/kg body wt) (80). Cases of toxicity of both vitamins E and K have been reported, but under ordinary circumstances these vitamins are considered relatively innocuous (81). 

A number of studies have shown that vitamins moderate the induction of chromosomal aberrations by radiation. Vitamins C and E given orally to mice either 2 h before, immediately after, or 2 h after 1 Gy (100 rad) of y-ray TBI significantly reduce the frequencies of micronuclei and chromosomal aberrations in BM cells. Vitamin E is the more effective (95). Administration of vitamins C and E within 5 min of irradiation is as effective as pretreatment. Protection by vitamin C has also been shown in humans. Whereas chronic treatment of rats using vitamin C (100 or 300 mg/(kg/d)) for six months prior to TBI protects against chromosomal aberrations, vitamin E is not radioprotective in this setting (96). 

There are numerous reports of the effects of antioxidant vitamins on transformation. Vitamin C suppresses x-ray-induced transformation when CSHlOTy cells are treated daily for one week following irradiation (97), suppresses transformation by y-rays or neutrons, and prevents the promotion of radiation-induced transformation by 12-0-tetradecanoylphorbol 13-acetate (TPA), but has no effect on cell survival (98). In these studies, the continuous presence of vitamin C for a critical period appears to be necessary for suppression of transformation. Vitamin C may act on the promotion stage of... 

Irradiated ergosterol was found not to be as antirachitic in the chick as in the rat, whereas the chick could be protected by direct kradiation. The provitamin in cholesterol was shown not to be ergosterol. Rygh (14) in 1935 found that 1 rat unit of cod Hver oil was 100 times more potent in chicks than 1 rat unit of vitamin D2. Brockmann (15) in 1936, prepared the pure crystalline 3,5-dinitrobenzoate derivative of vitamin D obtained from tuna Hver oil... 

Provitamin. The chemistry of the D vitamins is intimately involved with that of their precursors, the provitamins. The manufacture of the vitamins and their derivatives usually involves the synthesis of the provitamins, from which the vitamin is then generated by uv irradiation. The chemical and physical properties of the provitamins are discussed below, followed by the properties of the vitamins. 

The irradiation of calciferol in the presence of iodine leads to the formation of 5,6-/n7 j -vitaniin D2 [14449-19-5] (31) or [22350 1-0] (32) (67,68). 5,6-/ra j -Vitainin D as well as vitamin D (2) or (4) can be converted to isovitamin D by treatment with mineral or Lewis acids. Isocalciferol (35) [469-05-6] or (36) [42607-12-5] also forms upon heating of 5,6-/ -vitamin D. Isotachysterol (33) [469-06-7] or (34) [22350-43-2] forms from isocalciferol or vitamin D upon treatment with acid, and its production appears to be the result of sequential formation of trans- and isocalciferol from calciferol. These reactions are the basis of the antimony trichloride test for vitamin D (69—72). 

Commercially, the irradiation of the 5,7-diene provitamin to make vitamin D must be performed under conditions that optimize the production of the previtamin while avoiding the development of the unwated isomers. The optimization is achieved by controlling the extent of irradiation, as well as the wavelength of the light source. The best frequency for the irradiation to form previtamin is 295 nm (64—66). The unwanted conversion of previtamin to tachysterol is favored when 254 nm light is used. Sensitized irradiation, eg, with fluorenone, has been used to favor the reverse, triplet-state conversion of tachysterol to previtamin D (73,74). 

The solvent is then evaporated, and the unconverted sterol is recovered by precipitation from an appropriate solvent, eg, alcohol. The recovered sterol is reused in subsequent irradiations. The solvent is then evaporated to yield vitamin D resin. The resin is a pale yeUow-to-amber oil that flows freely when hot and becomes a brittie glass when cold the activity of commercial resin is 20 30 x 10 lU/g. The resin is formulated without further purification for use in animal feeds. Vitamin D can be crystallized to give the USP product from a mixture of hydrocarbon solvent and ahphatic nitrile, eg, benzene and acetonitrile, or from methyl formate (100,101). Chemical complexation has also been used for purification. 

Allylic bromination of pregnenolone acetate with dibromodi-methylhydantoin affords the 7-bromo compound (155) of undefined stereochemistry. Dehydrobromination by means of collidine followed by saponification affords the 5,7 endocyclic cis,cis-diene, 156. This compound contains the same chromophore as ergosterol, a steroid used as a vitamin D precursor. The latter displays a complex series of photochemical reactions among the known products is lumisterol, in which the stereochemistry at both C9 and Cio is inverted. Indeed, irradiation of 156 proceeds to give just such a product (158). This reaction can be rationalized by... 

Ergosterol occurs in plants and yeast and is important as a precursor of vitamin D (Figure 14—18). When irradiated with ultraviolet Hght, it acquires antirachitic properties consequent to the opening of ring B. 

Opposition to irradiated foods arises from two main concerns. In the process of killing microorganisms, irradiation might also destroy important nutrients such as vitamins. Secondly, irradiation produces ions and free radicals such as OH that may react with foodstuffs to generate harmful compounds such as... 

Savoure, N. et al., Vitamin A status and metabobsm of cutaneous polyamines in the hairless mouse after UV irradiation action of P-carotene and astaxanthin, Int. J. Vitamin Nutr. Res., 65, 79, 1995. 

---