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DISACCHAKIDES. 223
with yeast. With the phcnylhydrazine test it gives crystalline emu-
pounds which are not sufficiently characteristic (Thierfelder, P.
Mayer l
). By the action of 3 mol. phenylhydrazine and the necessary
amount of acetic acid upon 1 mol. glucuronic acid at 40° for a few days,
Neuber<; and Neimann obtained the glucuronic-acid osazone, which
was very similar to glucosazone and melted at 200-205°. With p-brom-
phenylhydrazine hydrochloride and sodium acetate, glucuronic acid gives
p-bromphenylhydrazine glucuronate, which is characterized by its insolu-
bility in absolute alcohol and by a very prominent levorotatory action.
This compound is very well suited for the detection of glucuronic acid.2
Dissolved in a mixture of alcohol and pyridine (0.2 gram substance in 4 cc.
pyridine and 6 cc. alcohol) the rotation is 7° 25’, which corresponds to
(a)o=— 309°. On distillation with hydrochloric acid, glucuronic acid
yields furfurol and also carbon dioxide, and on this behavior Tollens
and Lefevre 3
have based their quantitative method for the estimation
of glucuronic acid.
They give the pentose reactions with phloroglucin or orcin and hydrochloric
acid, and also a good reaction with naphthoresorcinol and hydrochloric acid
(see page 218). The product produced herewith is soluble in ether with a blue,
bluish-violet or reddish-violet color, and the solution shows an absorption band
somewhat to the right and on the D-line. According to Maxdel and Xeuberg 4
this reaction is not characteristic of glucuronic acid, as many aldehyde and ketone
acids give the same reaction; still, it is important in the differentiation of the
pentoses.
Glucuronic acid is best prepared from euxanthic acid, which decom-
poses on heating it with water to 120° C. for several hours. The nitrate
from the euxanthon is concentrated at 40° C, when the anhydride
gradually crystallizes out. On boiling the mother-liquor for some time
and evaporating further, the crystals of the lactone are obtained. In
regard to the quantitative estimation of glucuronic acid we must refer
the reader to the works of Tollens and his collaborators and of Neuberg
and Neimann.5
2. Disaccharides.
Some of the varieties of sugar belonging to this group occur ready
formed in nature. Thus we have saccharose and lactose. Some, on the
contrary, such as maltose and isomaltose, are produced by the partial
1
Thierfelder, Zeitschr. f. physiol. Chem., 11, 13, 15; P. Mayer, ibid., 29.
2
See Neuberg, Ber d. d. chem. Gesellsch., 32; and Mayer and Neuberg, Zeitschr.
f. physiol. Chem., 29.
3
Ber. d. d. chem. Gesellsch., 40.
4
Bioch. Zeitschr. 13.
6
Tollens, Zeitschr. f. physiol. Chem., 41, which cites also the older work; Neuberg
and Neimann, ibid., 44; Neuberg, ibid., 45.
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