The chemical nature of vitamin C

Abstract

THE object of this paper is to show that the antiscorbutic activity of our " hexuronic acid" preparations is due to the acid itself and not to a contamination by some more potent substance. The authors think that they have demonstrated this and that the experiments presented give definite evidence for the identity of the acid and vitamin C. In accordance with the latest results of chemical analysis [Karrer et al., 1933; Cox et al., 1932] "hexuronic acid" will henceforth be called ascorbic acid [Szent-Gyorgyi and Haworth, 1933]. PREPARATION OF ASCORBIC ACID FROM PAPRIEA. Progress in our work was dependent on the possibility of obtaining larger quantities of ascorbic acid. Unfortunately, adrenal glands, the only material heretofore suitable for large scale preparation, were not available in the necessary quantity. All our efforts to prepare ascorbic acid on the large scale from tomatoes, cabbages or oranges failed. In a quest for more suitable material, we have found that local varieties of paprika (Hungarian red pepper, Capsicum annuum) showed a strikingly high reducing power. 1 cc. of the juice of the fresh and ripe fruit reduces in acid solution on the average 2-4 cc. of 0.01 N iodine or the equivalent quantity of dibromophenolindophenol. This would correspond to about 2 mg. of ascorbic acid if this substance were solely responsible for the reduction. In animal experiments paprika juice shows a strong antiscorbutic activity. With 0-25 or 0 5 cc. of the juice, guinea-pigs were kept practically free from scurvy in a 53-day experiment (see Table II). Throughout this experiment the same juice was used, which was kept in vacuo at 00. This brings out the fact, that paprika juice not only contains relatively large amounts of the antiscorbutic factor, but also contains it in a relatively stable condition, suitable for chemical work. 50 kg. of paprika, freed from the core, were minced in a meat grinder and 1750 g. of barium acetate in the form of a hot saturated solution were added. After standing for an hour the pulp was pressed out in a fruit press, 40 litres of juice being obtained. In absence of air this juice is stable for a period of 2 to 3 weeks. In the decanted clear liquid, 5 % of normal lead acetate is dissolved and the solution made slightly alkaline to bromothymol blue with ammonia. The precipitate is sharply separated on the centrifuge, suspended in very little water and 25 % sulphuric acid added till the fluid colours thymol blue slightly red. The lead sulphate is removed by centrifuging and 10 % of barium acetate is dissolved in the liquid. The inactive precipitate is removed on the centrifuge.