Abstract
As biosynthesis of thiamine in isolated roots or sprouting seeds of certain kinds of plants had been shown by several groups, the authors sought for plant materials which were capable to build up thiamine from the pyrimidine and thiazole moieties on the incubation with their homogenate. It was found that sprouting radish was always proved to promote the biosynthesis while many other plant materials were less or not effective for the biosynthesis. Then germination of radish-seeds in sand culture was carried out with or without addition of 2-methyl-4-amino-5-hydroxymethylpyrimidine (I) and 4-methyl-5-β-hydroxyethylthiazole (II) (each 10^<-4>moles to 1g of seeds) and thiamine contents of radish increased to the maximal values when sprouts reached to the length of 7-9 cm. Comparing to the control without addition of I and II, simultaneous addition of the both was most effective and addition of I only was more effective than that of II to increase thiamine contents. Similar pyrimidineco mpounds hauing 5-formyl or 5-aminomethyl instead of the 5-hydroxymethyl radical of I, were shown to be less effective than I for biosynthesis of thiamine. Such thiazole-precursor as cysteine or methionine failed to promote the biosynthesis during germination of radish-seeds, when it was added to the culture with I. Biosynthesis of thiamine by combining I and II in sprouts of radish was one of the probable ways.
