The Ultraviolet Absorption of Vitamin K1 and the Effect of Light on the Vitamin

The relationship between chemical structure and ultraviolet absorption spectra is nowhere illustrated better than in the study of vitamin K and related compounds.One generalization which we presented in a previous publication (l), namely that the vitamin K absorption curve presents a summation of the benzenoid and the quinoid components of the disubstituted naphthoquinone molecule, recently has been extended by Morton and Earlam (2) to the anthraquinone series.We now have made a more complete study of the vitamin K1 absorption curve, using not only the vitamin isolated from natural sources, but also several specimens of the synthetic product.The main objects of the work were to check the identity of the natural and synthetic products and to determine whether the absorption curve, and especially the absorption coefficient at X 249 rnp, could be used as a measure of purity of the vitamin.It was hoped also that the results of this detailed study might clear up the controversy between Karrer (3,4) and Doisy (5,6) regarding the absorption coefficients of the pure vitamin.Obviously, in order to contribute to this question it was necessary to reinvestigate the complete structure of the absorption curve and to study the influence of light and other factors such as the presence of acetic acid which sometimes is added as a stabilizer. Apparatus and MaterialsThe samples of vitamin Kr, both natural and synthetic, used in this investigation were prepared by Doisy and his associates at the St. Louis University School of Medicine.They were examined with a Bausch and Lomb medium quartz spectrograph and ultraviolet sector photometer, with a Hilger No. H-698 hydrogen discharge tube as the source of continuous ultraviolet light.The hexane used as the solvent in this study was the Eastman Practical grade, which was purified and redistilled.The purification process consisted of five to ten shakings with 10 per cent fuming sulfuric acid, two washings with 10 per cent Na2C03 solution, prolonged shaking with 5 per cent KMnO*-10 per cent Na2C03 solution, fifteen to twenty washings with distilled water, drying for 24 hours over calcium oxide, and distillation 233