Saponarin : a new glucoside, coloured blue with iodine / by George Barger.

  • George Barger
Date:
[1906?]
Catalogue details

Licence: Public Domain Mark

Credit: Saponarin : a new glucoside, coloured blue with iodine / by George Barger. Source: Wellcome Collection.

    11/20 page 1218
    Theory for live acetyl groups requires acetic acid *58*1 and vitexin *59*3 per cent. The same acetyl derivative is obtained by the use of acetyl chloride in pyridine solution. Saponaretin. This substance is the chief product when saponarin is hydrolysed with dilute acids. Most of it separates from the acid solution on cool¬ ing in the form of a dark yellow syrup, and can be freed from accom¬ panying vitexin by alcohol as already described. If the alcoholic solution after separation of the vitexin is evaporated on the water- bath in a vacuum, a viscous syrup is left behind, but if this is re¬ dissolved in absolute alcohol and again evaporated, so as to remove all the water, the saponaretin can be obtained as a light yellow powder. After most of the saponaretin has been deposited as a thick syrup from the acid solution on cooling, further quantities separate out in the course of a few days as a pale yellow solid, which consists of minute, sphaero-crystals embedded in a gelatinous matrix. After filtering it can be purified by redissolving in boiling water and allow¬ ing to cool, when it separates again in the same form, without ever assuming a definitely crystalline form. When the moist substance is heated, it melts below 100° and forms a resin. If, however, it is first dried at the ordinary temperature in a vacuum, the jelly shrinks very much and darkens. It can then be heated without melting to above 200°, and it is gradually decomposed at a higher temperature without showing a true melting point. Saponaretin has not yet been obtained pure. From its hot aqueous solution it separates as a syrup, from a cold solution as a jelly. In alcohol it is extremely soluble, and, although crystals are formed when a concentrated solution is allowed to evaporate slowly, these crystals could not be freed from the mother liquor. Saponaretin is insoluble in most other organic solvents, and from mixtures of such solvents with alcohol it always separates as a jelly. On acetylation, a very soluble acetyl compound is obtained which melts at a low temperature and could not be cry>tallised, nor could other crystalline derivatives be isolated. In other respects the substance closely resembles vitexin, for instance, in its behaviour with alkalis and with ferric chloride. At first it was supposed that the two substances differed by a molecule of water, but saponaretin also seems to have the formula C15Hu07, although, as the substance was amorphous, conclusive proof is wanting. For analysis, the substance was twice allowed to separate in the gelatinous condition from water, and was then dried in air and finally in a vacuum over sulphuric acid, when it underwent a further
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