Chromatographic Separation of Five Vitamin A1 Isomers from the Eyes of Deep‐Water Prawns (Pandalus Borealis).

Summary. In fractional chromatography of the unsaponifiable fraction from the eyes of deep water prawns the vitamin A1 present was found to separate into five components: a, b, c, d, and e. In two instances the relative proportions of the different isomers present, expressed by E325 measured on the collected fractions were found by chromatography to be as follows: 1. a:b:c:e = 0.8:52:9:38 (d was incompletely separated from c and e, the quantity of d may be estimated to be about 0.5—1 %). 2. a:b:c:d:e = 1.5:49:17:1.5:31. The results obtained suggest that substances a, b, c, and e are identical with 11.13‐di‐cis, 11‐mono‐cis, 13‐mono‐cis and all‐trans vitamin A1. respectively, while the small quantities of substance d available have rendered the identification of this substance less certain. The possibility that substance d is 9,13‐di‐cis vitamin A1 is discussed. In a preparation marketed by Messrs. Hoffmann‐La Roche & Co., Basle, under the name of “Vitamin A, Feed Grade”, the presence has been ascertained of an isomer the properties of which agree with those of substance a and 11,13‐di‐cis vitamin A1. The substances obtained were subjected to a number of identification tests: isomerization with iodine as catalyst, formation of anhydro vitamin by means of hydrogen chloride, determination of E620.,mμ Carr‐Price/En. v. max. and the maleic anhydride reaction. The spectrophotometry properties of the substances have also been examined for the purpose of establishing their identity.