Lxxvii. Experiments on the Synthesis of Hyoscyamine in Atropa Belladonna by Benjamin

THE recent observations of Klein & Linser [1932; 1933, 1, 2] on the betaines stachydrine and trigonelline in Stachys palustris and Trigonella Foenum-graecum point to the fact that these substances are intimately connected with protein metabolism. These workers showed that proline and ornithine when injected into the plant caused increases in the concentrations of stachydrine and trigonelline. Other amino-acids were without effect. They also found that when stems of Nicotiana were placed in a solution of proline an increase in nicotine content took place. Furthermore, as the result of experiments on the trigonelline content of various plants throughout their life history, Klein & Linser conclude that the fluctuations which were recorded indicated utilization of the alkaloid as a nitrogenous reserve. In a previous publication by the present writer [Cromwell, 1933] an account was given of a series of experiments made on Berberis Darwinii with the object of investigating the problem of the synthesis and function of the alkaloid berberine. The results of this work appeared to show that in Berberis Darwinii the alkaloid does not function as a nitrogenous reserve and that synthesis is dependent on condensation of sugar residues with protein intermediates. Although Berberis Darwinii provides satisfactory material for stem and root experiments on alkaloid content it is not an ideal plant for experiments on leaves for two reasons. Firstly, the half-leaf method of sampling cannot be adopted on account of the smallness of the leaves, and secondly the leaves contain large amounts of colouring matter and resins which create difficulties in analysis. It was therefore considered desirable to carry out experiments on an alkaloid-producing plant the leaves of which did not possess the disadvantages of Berberis Darwinii. Accordingly Atropa Belladonna, which possesses large bilaterally symmetrical leaves, was chosen with a view to extending and testing the theory that the alkaloid molecule is synthesized partly from sugar residues and partly from protein residues. All parts of Atropa Belladonna contain hyoscyamine which in the process of extraction is largely converted into its racemic modification atropine. Experiments have been carried out to determine the effects on the hyoscyamine content of (a) withdrawal of certain essential elements from the culture medium, (b) presentation of specific organic sources of nitrogen, (c) presentation of certain inorganic sources of nitrogen, (d) feeding with a combined solution of glucose and potassium nitrate, (e) etiolation, involving both feeding and starvation experiments.