Absorption spectra of substances derived from vitamin A

Abstract

IN continuation of earlier work on vitamin A we have investigated the ultraviolet absorption of certain products obtained after the vitamin has been decomposed. At the same time, we have tried to elucidate the mechanism of the antimony trichloride colour test.As is well known, the blue colour is transient, and for purposes of assay it is necessary to determine the intensity of colour during the first minute, as otherwise the rapid fading tends to vitiate the results. Little is known concerning the secondary reactions which occur, and even the primary process is not fully understood. For the full development of the blue colour, the reagent must be nearly saturated and, it would appear, the SbCl3/vitamin A ratio must be very high (order 20,000: 1). This fact suggests that the blue substance (or substances) is an addition compound; the hypothesis of more than one coloured addition complex has already been advanced to account for the two apparently independent absorption bands seen in the blue solutions [Gillam and Morton, 1931;Heilbron, Gillam and Morton, 1931]. It is possible that the primary process, resulting in the blue colour, leaves the vitamin A molecule intact, whilst the secondary reactions associated with the fading of the colour bring about decomposition. To test this view, the blue solutions have been poured into large volumes of water so that the antimony is precipitated as oxychloride. The organic matter is then recovered and its properties studied.The general method adopted is as follows. A known weight of liver oil or concentrate dissolved in chloroform is treated with a saturated solution of antimony trichloride in chloroform and the mixture shaken for one minute to allow the blue colour to develop fully. The solution is then poured into water in a separating funnel and shaken vigorously to complete the decomposition of the antimony trichloride. As it is impossible to separate the chloroform layer owing to the precipitated antimony oxychloride, the latter is brought into solution by careful addition of concentrated hydrochloric acid, when separation into two layers readily occurs. The chloroform extract is washed successively with sodium carbonate and water and dried over sodium sulphate. After removal of solvent, the residual oil (or concentrate) is very similar in appearance to the original material and in all cases gives a blue or

Anhydroretinol: a naturally occurring inhibitor of lymphocyte physiology.

“…Thus, AR does not appear to arise from spontaneous dehydration but is enzymatically derived. In the test tube, however, AR is easily synthesized from retinol by acid-catalyzed dehydration (18).…”

“…AR was in fact the first retro-retinoid discovered in nature. AR was produced from all-trans retinol by hydrochloric acid catalyzed dehydration as described (18), and the all.trans isomer was purified to homogeneity by reversed-phase high pressure liquid chromatography. Human B ]ymphoblastoid cells (e.g., cell line 5/2) were cuhured in medium RPM1 1640 with 7% FCS.…”

“…A second run on an analytical Cls column fielded pure AR. Its UV spectrum showed a characteristic vibronic fine structure with maxima at 351, asoo0-368, and 390 nm (17,18). Mass spectroscopy and proton nuclear magnetic resonance confirmed the structure (Derguini, F., manuscript in preparation).…”

Kinetics of formation of anhydrovitamin A from vitamin A alcohol and its acetate**School of Pharmacy, University of Wisconsin, Madison

“…Effect of Hydrogen Chloride on the Formation of Anhydrovitamin A.-The qualitative effect of hydrogen chloride on the dehydration of vitamin A alcohol in ethanol was reported in the original work on anhydrovitamin A formation (1,4). Hydrogen chloride also catalyzes the formation of the anhydro compound from vitamin A acetate, although the rate of the reaction with the alcohol is about 30 times faster than that with the ester.…”

Adsorption experiments with vitamin A concentrates

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THE unsaponifiable matter of halibut-liver oil, after removal of the major part of the sterols, is a viscid orange-brown oil containing 60-70 % vitamin A, which on fractional distillation yields a pale yellow oil [Heilbron et al, 1932]. If the vitamin concentrate, whether purified by distillation or not, be dissolved in light petroleum and passed through a column packed with adsorbent (A1203 or Ca(OH)2) a red zone appears.

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