1. A method of quantitative estimation of TAD or TPD was described, and the effects of various conditions were reported.
2. TAD or TPD added to blood is easily converted into thiamine.
3. Before the TAD or TPD added to blood are reduced to thiamine, SSB₁ is formed as an intermediary product, which can be detected by paper chromatography.

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The amounts of riboflavin, both free and esterified, excreted in urine and feces of an individual, fed for one week each either an ordinary, or a vegetable or a meat diet, containing approximately neccessary amounts of nutrients and vitamins, were examined.
When the same ordinary diet is taken, the amounts of riboflavin excreted In urine and feces are relatively constant. It consists of about 70% of the free and 30% of the estersfied form both in urine and in feces. When vegetable diet is taken, the amount of urinary riboflavin does not change markedly, but that in the feces increases to about 5 times in a week, whereby the amount of feces increases to about 3 times. When the vegetable diet is changed into the ordinary one, a return to the initial state takes place within about 3 days. When the meat diet is taken, the urinary riboflavin rises remarkably, contrary to the vegetable one, but the fecal riboflavin decreases slightly. When the meat diet is changed into the ordinary one, the riboflavin content in the urine decreases rapidly.
From the above, it can be concluded that vegetable diets enhance markedly the riboflavin synthesis by intestinal bacteria.

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B₆-group vitamins have a strong atoxopyrimidine action, stronger in PIN than in PAM. TXP intoxication may fully be prevented by a simultaneous injection of PIN in amount of 1/20 of the dose of TXP.
The biological antagonism based upon the structural similarity was discussed.

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In order to study the conversion of tryptophan to niacin, the daily urinary excretions of niacin, N-MNA and 6-pyridone were determined of a subject ingesting the experimental diet and their changes were estimated after adding 2g of L-tryptophan, 2g of D-tryptophan and 50mg of niacinamide, respectively, in succession after 4-5 days'interval.
The following results were thus obtained:
(1) The administration of L-tryptophan raised the urinary excretion of niacin derivatives markedly during the first day, decreasing then gradually from the next day in the order of niacin, N-MNA and 6-pyridone.
(2) D-Tryptophan was also converted into niacin though somewhat slower in rate. Maximum excretion of niacin derivatives was observed on the second day after its administration.

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1. For extracting antithiamine factors from dried fern powder, phosphate buffer of pH 7 is satisfactory.
2. The optimum pH of fern extract is 7. If the pH is higher than 7, thiamine decomposition increases, but thiamine is decomposed by alkali alone without fern extract, so that the investigation of the thermostable factor can not be performed exactly at pH higher than 7.
3. The thiamine decomposition by fern extract increases progressively with rise in temperature. But between 50° and 60° the decomposition remains the same, the curve showing an inflexion.
4. When the fern extract is heated at 100° for 30 minutes, 80% of the activity remains, no further change taking place by heating for 2 hours. At 200°, 70% of the activity is preserved even when heating lasts for 1 or 16 hours. At 300°, the activity is retained to only 6%, while it is entirely lost after carbonization or incineration.
5. When fern extract is heated at 100° for 30 minutes, the thermolabile factor is inactivated. With rise in pH, thiamine decomposition increases progressively, and at pH 6 no decomposition can be detected. At pH 6, therefore, the extract shows the activity of the thermolabile factor alone.
6. The optimum temperature for the thermolabile factor is 50° in the experiments of one hour, but the activity of the thermostable factor increases with the rise of temperature up to 100°.
7. Thiochrome is found by paper chromatography to be one of the decomposition products of thiamine by thermostable factor. Thiazolone can not be an intermediate to thiochrome formation.
8. The thermostable factor is dialysable through cellophane, contrary to the thermolabile factor.
9. The activity of the thermolabile factor is not influenced by the presence of oxygen, while the thermolabile factor shows enhancement of activity in its presence.
10. The decomposed thiamine produced by the action of fern extract can not be turned to thiamine by the action of Takadiastase, indicating that the transformed product can not be an esterified thiamine.
11. The activities of both factors are interrupted instantly by 1N HCl or 25% KCl in 0.1N HCl.
12. The activity of the thermolabile factor is activated by various organic bases, while that of the thermostable factor is not influenced by them in most cases. The behaviors of the thermolabile factor resembles in some respects to shellfish and bacterial thiaminase, but there are also some differences. Complete agreement was not observed with any known thiaminase.
13. For the extraction of the thermolabile factor, phosphate buffer of pH 7, chloroform water (pH about 8) or 10% acetone water is suitable. For the extraction of the thermostable factor chloroform water is most satisfactory. Acetone water is of next choice, while buffer solution is not beneficial.
14. Like thiaminase, the thermolabile factor produces heteropyrithiamine by incubating with pyridine and thiamine, contrary to the thermostable factor.
15. When the thermolabile factor is incubated with pyrimidylmethyl base and the thiazole moiety of thiamine, thiamine synthesis takes place, but the amount synthesized is not always parallel with the degree of activation of the enzyme by bases.

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In order to clarify the photodecomposition mechanism of riboflavin, detection and determination of photolytic products were made.
(1) In neutral solution, the photolytic products, calculated on the basis of 1M of initial riboflavin, were as follows: 0.82M of lumichrome, 0.74M of formaldehyde, 0.09M of formic acid and about 1M of sugar, probably erythrose.
Lumiflavin, acetaldehyde, acetic acid and volatile alcohols could not be detected.
(2) From the solution irradiated in an alkaline medium, 0.65M of lumiflavin, 0.09M of lumichrome, 0.1M of formaldehyde and 0.06M formic acid were detected. Besides, four carbon compounds, probably mixtures of erythrose and erythronic acid, were produced. Acetaldehyde, acetic acid and volatile alcohols were absent.
From these results, it may be considered that formaldehyde is produced accompanying lumichrome. Accordingly, the following photodecomposition mechanism of riboflavin is conceived:
At first, hydroxylated carbon at position 2′ is oxidized to carbonyl group. Then, hydrolytic rupture of carbon-carbon bond occurs between 1′ and 2′. At that time, hydroxyl group is bound to flavin-methylene radical, forming 9-hydroxymethyl flavin which converts instantly to lumichrome by liberating formaldehyde in lumichromic cleavage. On the other hand, in lumiflavinic cleavage, flavin-methylene group combines with proton, forming flavin-methyl compound known as lumiflavin. Existence of formic acid may be resulted by a further oxidation of a part of formaldehyde once produced.

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We investigated allithiamine and thiamine propyl disulfide polarographically. Both represented the polarographic reduction wave at the whole pH range, having the properties of the general disulfide compound. The former showed a catalytic wave in cobalt salt solution, while the latter no catalytic wave at 20°.

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Bacillus thiaminolyticus was given daily to hens. Thiaminase appeared in their intestines and the symptoms of thiamine deficiency developed.

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It is confirmed by paper chromatography that the violet-fluorescent substance (V substance) produced by Eremothecium ashbyii is different from three 2-amino-4-hydroxy-pteridine derivatives, i.e. 6-methyl-, 7-methyl-, and 6-carboxylic acid. It is thermostable and photoresistant, especially on neutral to acid side. It is decomposed by oxidizing agents and becomes a non-fluorescent substance by reduction, which restores fluorescence by aeration, indicating it to be a reversible redox substance. The relationship between pH and fluorescence intensity, as well as absorption spectrum furnished an important basis for presuming its structure.

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The life cycle of the Bacillus aneurinolyticus Kimura et Aoyama was pursued from the vegetative cell to the free spore, using the electron microscope and the process of the sporulation has been described in detail.
At the final stage of sporulation, a phenomenon conventionally called the “burst” was demonstrated and its significant relationship to aneurinase production in the culture media was discussed.

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1. A synthetic medium for producing riboflavin without a fixing agent such as CaCO₃ was proposed.
2. The minimum concentration of iron salts revealing complete inhibition of riboflavin production was found to be the same (1.8×10^-5M) for ferrous and ferric ions, and 9.0×10^-5M for ferricyanide.
3. Various kinds of growth factors as biotin, folic acid, p-aminobenzoic acid, calcium pantothenate, thiamine, pyridoxine, vitamin B₁₂, nicotinic acid and phytic acid or a fixing agent such as CaCO₃ could not reveal any antagonistic effect on ferrous sulfate.
4. Iron reduces the ratio of butanol to acetone from 5.71 to 2.65, and the reduction was not attributable to the indirect action of riboflavin, but was probably due to the direct action of iron salt on bacterial metabolism.
5. Inhibition of iron salt would probably be due to poisonous effect on riboflavin producing enzyme, since such a small quantity of iron revealed a complete inhibition of riboflavin production immediately after adding the salt.

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1. After administering tryptophan to albino rats fed on a B₆ deficient diet containing casein, xanthurenic acid is excreted in the urine.
2. Feeding rats on a diet containing much fatty acid salt and tryptophan, they become deficient in vitamin B₆ and a remarkable amount of xanthurenic acid is excreted in the urine, which was isolated and identified. After the administration of pyridoxine, the urinary excretion of xanthurenic acid remarkably decreased but never completely disappeared.
3. After administering orally both sodium butyrate and tryptophan to albino rats, the blood sugar curve show primary hyperglycemia, followed by temporary hypoglycemia, and finally definite hyperglycemia, accompanied by glycosuria owing to the production of xanthurenic acid.
4. Administration of xanthurenic acid to albino rat leads also to the development of diabetic symptoms.
5. Xanthurenic acid, when given continuously, shows an accumulative effect on diabetic symptoms. In the urine of the rats in hyperglycemia and vitamin B₆ deficiency, a definite increase of acetone bodies is detected.
6. The pancreas of rat showing hyperglycemia after feeding for a long period on high fat and casein diet or vitamin B₆ deficient one, showed histologically degenerative changes of β-cells of Langerhans islets. It was especially conspicuous in vitamin B₆ deficiency.
7. In the urines of diabetic patients, the spot corresponding to free form of xanthurenic acid was detected by paper chromatography, contrary to the healthy subjects.
8 Insulin was found to prevent the urinary excretion of xanthurenic acid of experimental animals as detected by paper chromatography. The product excreted in the urine instead of xanthurenic acid was proved to be kynurenic acid.
9. Methionine inhibit the formation of xanthurenic acid. By simultaneous application of methionine and pyridoxine to rats, the urinary xanthurenic acid disappeared completely.
10. The xanthurenic acid injected to rat is readily excreted in the urine. An enzyme, xanthurenicase, was found in rabbit liver.
11. The injected xanthurenic acid is excreted in conjugated forms as non-toxic substances.

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