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Vitamin B
Editor’s Note
There are eight separate chemical compounds in the family of B vitamins, but all were once thought to be a single substance, deemed essential for the growth of organisms. This anonymous report describes how that former picture began to change. Following work that suggested vitamin B had two forms that relieve pain and a concatenation of ailments called pellagra, it seemed by this stage that there were at least four B vitamins. Vitamin B 1 (thiamine), the focus here, was the best characterised, its chemical composition and properties being already sketchily known. Vitamin chemistry became an important strand of biochemistry in the prewar era, although it was some time before their molecular structures and physiological roles were understood. 中文
THE separation of vitamin B into two factors, antineuritic and antipellagrous, a few years ago, led to considerable attention being devoted to the properties of this vitamin, with the result that it is now possible to distinguish at least four B factors, quite apart from any grouped under the name “Bios”, which may be necessary for the growth of lower organisms. The factors are distinguished by differences in their chemical properties and physiological effects: their differentiation has necessitated a revision of the methods of assay, since it is possible that a failure to respond to an addition to the diet is an indication of the absence of a factor other than that for which the test was designed. In this type of research a preventive test is less delicate than a curative, whilst the growth test may be considered still cruder: a single factor should cure the specific symptoms due to its absence, preventive tests may test for more than one, whilst it is clear that a positive growth response can only be obtained when every factor is adequately supplied; and our knowledge of all the factors required for growth is still incomplete, as the recent work on vitamin B has shown. 中文
H. W. Kinnersley, R. A. Peters, and V. Reader 1 have analysed the pigeon curative test for vitamin B 1 , or the antineuritic factor. By adherence to certain principles, the test can be made reasonably accurate and has been successfully used in following the vitamin in its concentration from a yeast extract. The birds should be in the laboratory for a month on a mixed grain diet before being placed on the diet of polished rice, and only those developing symptoms within 30 days should be used. As soon as signs of head retraction appear, the bird should be transferred to a warm room for 2 hours and given 50 mgm. glucose in water by stomach tube: this procedure eliminates birds showing false cures. The dose of extract must be given within 6-12 hours of the onset of symptoms and, provided the cure lasts more than 1 and less than 10 days, the amount of active principle present can be considered as directly proportional to the length of the cure. After the test is over, the bird is given marmite and kept warm for a few days. It is then placed on the stock diet again for about a month, when it is ready for another period of polished rice feeding. Individual birds show a remarkable constancy in the time symptoms appear after commencement of the experimental diet, but there is no correlation between this interval and the duration of the subsequent cure, or between it and the colour or weight of the bird. 中文
H. Chick and M. H. Roscoe 2 have used the growth of young rats as a criterion for the presence of vitamin B 1 . It is difficult to carry out a curative test with this animal, since there is only a very short interval between the onset of acute symptoms and death: Reader has, however, been successful and has found that the adult rat requires about one pigeon day dose each day (quoted by Peters, the Harben Lectures, 1929). Chick and Roscoe used synthetic diets free from vitamin B 1 : vitamin B 2 was supplied as autoclaved yeast or as fresh egg-white. After 2-3 weeks the animals began to lose weight: growth was resumed if Peters’ antineuritic concentrate was then administered. The egg-white diet, however, did not maintain growth to maturity. B. C. Guha and J. C. Drummond 3 have used both the pigeon curative and the rat growth tests: in the latter, vitamin B 2 was supplied as marmite autoclaved at an alkaline reaction. 中文
Chick and Roscoe 4 have used a similar method for the assay of vitamin B 2 , young rats being placed on a diet complete except for this vitamin, and the B 1 factor being supplied as Peters’ concentrate. It was found that the caseinogen used contained traces of vitamin B 2 unless it was reprecipitated with acetic acid and thoroughly extracted with alcohol before being heated at 120°. Animals on this diet fail to grow but respond to a supplement containing vitamin B 2 . If the supplement is not given, after about six weeks a generalised dermatitis appears, which can be cured by administration of the vitamin. 中文
B. C. P. Jansen and W. F. Donath 5 obtained highly active preparations of vitamin B 1 from rice polishings by a process involving extraction with acid water, adsorption on fuller's earth, eleution with baryta, and fractionation of the extract with silver sulphate and baryta. The activity was precipitated with phosphotungstic acid, the precipitate decomposed with baryta, and after removal of barium the concentrated solution was treated with platinic chloride, which precipitated the vitamin. Further purification was effected by acetone precipitation from alcoholic solution and by treatment with picrolonic acid or gold chloride. 0.012 mgm. of the final fraction a day was sufficient to maintain pigeons in health over six weeks: C. Eykman 6 confirmed the activity with both pigeons and cocks. The final product was obtained in crystalline form, as a hydrochloride, a picrolonate, or a double salt with gold chloride. 中文
Kinnersley and Peters 7 have continued their work on antineuritic yeast concentrates 8 . It is not yet certain whether the curative substance is the same as that obtained from rice polishings by Jansen and Donath: the activity of the final product does not appear to be quite so great and its properties are not quite the same. In all work on the concentration of vitamin B 1 , it has been found that the properties of the active fractions vary according to the nature of the accompanying impurities, so that methods developed for use with an extract of rice polishings may not be applicable without modification to an extract of yeast. The extract from the charcoal adsorption, after removal of metals, can be fractionated by successive additions of alcohol, the vitamin passing into the portion soluble in 99 percent ethyl alcohol. The authors failed to get consistently successful results with a silver fractionation, but were more successful with the use of phosphotungstic acid and platinic chloride. The most active preparations contained a day dose in 0.027 mgm., but more lately some have been obtained with a curative activity of 0.01 mgm. a day dose. 中文
Guha and Drummond ( loc. cit .) prepared active concentrates from wheat embryo. After extraction by means of acid alcohol, two different methods of concentration were employed: in the first, impurities were precipitated by lead acetate, and the activity adsorbed on norite charcoal at p H 4.5 and eleuted with acid alcohol: it was then precipitated by phosphotungstic acid, adsorbed on silver oxide, and the product fractionated with alcohol. Picrolonic acid then precipitated impurities from the material, which was soluble in alcohol. The first product had a pigeon day dose of 0.043 mgm. In the second method, Jansen and Donath's process was followed, namely, adsorption on fuller's earth at p H 4.5 and eleution with baryta, and fractionation with silver nitrate and baryta followed by precipitation with phosphotungstic acid. The product was then submitted to precipitation with platinic chloride, followed by gold chloride; at the last stage most of the activity passed into the precipitate, but it was observed that smaller doses of both precipitate and filtrate together restored growth in the rat or cured the pigeon than of either when given separately, suggesting that vitamin B 1 may itself be composed of more than one factor. The smallest pigeon day dose was 0.0025 mgm., and 0.015 mgm. promoted good growth in rats. These figures indicate that the preparations were more active than the crystals obtained by Jansen and Donath. 中文
Although formulae have been assigned to vitamin B 1 preparations, it does not appear that a pure substance has yet been isolated. A certain amount is, however, known about its properties. It appears to be a tertiary base: it is soluble in water and alcohol, but is unstable in the latter solvent when highly purified: it is insoluble in the other common organic solvents. It is destroyed by alkali, but is stable to oxidising and reducing reagents and to nitrous acid. Cruder preparations give a definite Pauly reaction, but as purification proceeds the reaction becomes very weak. Sulphur is absent, and the purer preparations do not give the xanthoproteic, purine, or Millon's reactions. In extracts from rice polishings, after treatment with lead acetate and concentration of the filtrate, vitamin B 1 is destroyed by fermentation and by heating to 95°, and is removed by filtration through a Berkefeld filter 9 , although it will dialyse through cellophane. 中文
The isolation from concentrates of supposedly pure substances and the fact that false positives may be given by the pigeon test have led to claims that different pure compounds are the vitamin. J. M. Gulland and Peters 10 have examined the claims that certain quinoline and glyoxaline derivatives have curative properties. Without exception all those examined, including 4 (or 5) glyoxaline methylethyl carbinol hydrochloride and 2:6-dihydroxyquinoline, were quite inactive when tested on pigeons by Peters’ technique. 中文
( 127 , 95-96; 1931)
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