Chemical investigations of the "Gifblaar" Dichapetalum cymosum (Hook) Engl. I

Abstract

Although the investigations recorded in this paper have not resulted in the isolation of the toxic principle of the Gifblaar, Dichapetalum cymosum in a state of chemical purity, it is felt that certain valuable information has been obtained relative to the nature of this toxin. In addition, some interesting substances have been isolated from the plant in the course of chemical manipulations. These include: (1) A catechol tannin. (2) A yellow colouring matter, shown to be a methylpentoside, yielding rhamnose on hydrolysis. (3) A histidine-like base. (4) A base probably identical with choline. (5) The alkaloid trigonelline, the methyl-betaine of nicotinic acid. Various specialised methods were tried for the purification of the toxin, including: (1) Dialysis. (2) Ultrafiltration under pressures up to 80 atmospheres of nitrogen. (3) High-vacuum distillation and sublimation. (4) Continuous extraction with butyl alcohol, etc. Certain other chemical operations led to the conclusion that the following groups are definitely absent from the toxin molecule: Carboxyl –COOH; Ketonic >CO; Aldehyde –CHO; Hydroxyl –OH; Amino –NH₂; Imino >NH. The active principle almost certainly contains nitrogen and it is suggested that this may be included in some cyclic structure. It may possibly occur as in tertiary bases but the molecule, as a whole, does not evince basic characters. Preparations, still highly toxic to rabbits, have been prepared containing no protein, amino-acid, or carbohydrate material, impurities which had not before been successfully removed. The chemical stability or inertness of the toxic substance is very remarkable in view of its pronounced physiological action. Thus, it resists boiling for one hour with 1 per cent. sulphuric acid or 1 per cent. sodium hydroxide solutions; it is not oxidised by potassium permanganate or by hydrogen peroxide in the cold and it is thermostable. In view of this stability and the absence of any substance known to combine with or precipitate the toxin, the hope of finding any specific prophylactic or curative substance for use in Gifblaar poisoning becomes very remote indeed.