The Alkaloidal Constituents of Gelsemium sempervirens With an Additional Paper: Fission and Molecular Rearrangement as Alternate Modes of Reaction

Marrian, Stanley Frederic (1942) The Alkaloidal Constituents of Gelsemium sempervirens With an Additional Paper: Fission and Molecular Rearrangement as Alternate Modes of Reaction. PhD thesis, University of Glasgow.

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The starting material for this investigation consisted of 22.5 kilograms of the dry powdered root of Gelsemium sempervirens, Aiton, and the object of the work was the isolation of the alkaloidal constituents of the root, followed by their chemical investigation. On account of the fact that sempervirine is unstable to heat, and is resinified to a large extent in boiling alcohol, it was decided, after some preliminary experiments, to carry out an extraction first of all with cold rectified spirit, followed by an extraction with boiling alcohol. It was decided also to use the method of separation (14) devised by Sayre for the isolation of gelsemine, sempervirine, and the amorphous alkaloids, and also to attempt the isolation of gelsemicine from the gelsemine mother liquors as described by Chou (15) , with certain small modifications in each case. This was done and the yields of gelsemine and sempervirine were found to be very much larger than those recorded by Sayre, particularly in the case of the latter. This was due, presumably, to the employment of a cold alcoholic extraction. The yield of gelsemine obtained was 0. 13% compared with 0.07% recorded by Sayre (14) and that of sempervirine (as nitrate) was 0.084% compared with 0.026% reported by Sayre. A small quantity of an amorphous alkaloid, not previously reported, was found in the gelsemine fraction, but could not be obtained crystalline. This alkaloid was found to be very slightly soluble in water and alcohol on long heating. The melting point of this amorphous alkaloid is 324d. An amorphous piorate was formed from water but could not be crystallised. On evaporating this alkaloid to dryness with hydrochloric acid a crystalline hydrochloride was formed, melting above 340, but owing to the extreme solubility of this hydrochloride and the small amount available, it was not found possible to prepare a sufficient quantity of the pure material for analysis determinations. Prom the fraction of the amorphous alkaloids called gelsemoidine by Sayre, there has been isolated a crystalline methiodide not previously reported. Analysis figures for this methiodide indicate a formula of either C20H24O3N2. CH3I or C20H22O3N2. CH3I. The melting point of this methiodide suggests its identity with apogelsemine methiodide C20H24O3N2. CH3I (melting points 296-297d. and 295d. respectively), but the determination of its specific rotation would seem to discount this view. The value Moore (11) has found for the specific rotation of apogelsemine methiodide is [x]D+12.4. An attempt was made to repeat, as far as possible, the conditions employed by Moore for apogelsemine methiodide, for the determination of the specific rotation of "gelsemoidine" methiodide. This has, however, been found impossible, the new methiodide being less soluble in water than apogelsemine methiodide has been recorded to be. A saturated solution was used for the determination and a value of [a]20D +3.9 was found. For comparison purposes the specific rotation of gelsemine methiodide was determined, and found to differ slightly from Moore's value. The value found was [a]10D+6.0, compared with that of [a]D +8.9 recorded by Moore(10). These results for gelsemine methiodide are in much closer agreement than those for "gelsemoidine" methiodide and apogelsemine methiodide, and it seems possible that the methiodide isolated from the gelsemoidine fraction is not, in fact, identical with apogelsemine methiodide. This possibility is, to a certain extent, enhanced by the fact that neither Sayre nor the present author were able to obtain "gelsemoidine" hydrochloride in the crystalline state, whereas apogelsemine hydrochloride is a crystalline substance. No attempt was made to prepare apogelsemine methiodide for comparison purposes as, for the isolation of pure apogelsemine, a relatively large expenditure of gelsemine would have been involved. The attempted isolation of gelsemicine was not successful, this fraction consisting of a dark brown tarry material which contained some gelsemine.

Item Type: Thesis (PhD)
Qualification Level: Doctoral
Keywords: Plant sciences, Biochemistry
Date of Award: 1942
Depositing User: Enlighten Team
Unique ID: glathesis:1942-79547
Copyright: Copyright of this thesis is held by the author.
Date Deposited: 04 Mar 2020 17:02
Last Modified: 04 Mar 2020 17:02

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