This is interesting if you're any good at french. https://archive.org/stream/bulletindelasoc181frangoog#page/n...
My french is mediocre at best and needs supplementation with google translate, but here's my stab at the relevant parts in english with some
adjustment so it reads more smoothly.
II. The authors mentioned the possibility of obtaining juglone by sublimation of the ethereal extract of the fruit.
III. The third method which is the one currently used to prepare juglone, was described in 1885 by Bernthsen and A. Semper. Ripe walnuts in September,
coarsely ground, are soaked for several days in ether, in proportions of 4kg nuts to 3kg ether.
The resulting greenish-brown solution is then oxidized using the following chromic mixture:
10g Potassium Dichromate, 13g sulfuric acid monohydrate (?. That would be about 84% acid), 500ml distilled water.
After the oxidation, the solution becomes reddish yellow, the hydrojuglone having turned into juglone. The ether is distilled and the residue taken up
in a small quantity of boiling ether, filtered hot, and evaporated. The residue is taken up in chloroform and mixed with an equal amount of petroleum
ether, which eliminates a mucilagenous material which appears to influence the crystallization. After filtering, the solution is evaporated under
vaccuum to give juglone.
The procedure of Vogel and Reischauer has the advantage that it gives a very pure product, but the yield is small.
Juglone is an extremely alterable material. It is reduced with great ease and is transformed into hydrojuglone. It also decays very quickly
when in contact with water or alcohol. In several day old fruit, the decomposition is already very appreciable. When we express these fruits, the
juglone, being found not only in contact with water, but also with the abundant organic matter which constitutes a strongly reductive medium is
transformed almost completely into hydrojuglone after a few minutes of rest.
The extraction of the juice by means of ether then provides a liquid very rich in hydrojuglone that contain only traces of juglone.
The procedure of Bernthsen and Demper furnishes a much higher yield. By oxidizing the ethereal extract of the pericarps, we obtain the totality of the
juglon contained in these organs, either in the state of juglone, or in the state of hydrojuglone. However, the product thus prepared is very impure.
The juglone obtained by this process in commerce is yellow green and can be prepared in a greater state of purity, through many crystallizations in
various solvents. It is very yellow red at the time of its preparation but it does not take long to decompose and within a few days of preparation, it
is partly converted into hydrojuglone and has the greenish color that compound.
New process - first method.
The nuts should be harvested with care, avoiding as much as possible, too many crushed pericarps. They should be detached at the time of extraction
and immediately immersed in the ether.
These precautions are intended to prevent the decomposition of juglone and transformation into hydrojuglone. The ethereal solution thus obtained is
very strongly yellow in color. The ether is distilled off and the residue is immediately taken up in benzene. This step leaves many impurities
insoluble, among which is most of the chlorophyll. The benzene extraction should happen immediately after the evaporation of the last traces of ether,
since juglone, which is impregnated with water and various organic matter at a fairly high temperature, would decompose rapidly.
[Edited on 9-9-2018 by UC235] |
