244 



NATURE 



[October 20, 192 1 



The Vegetable Alkaloids. 



It should not be impossible to bring the skeleton 

 of these transformations within the mental horizon 

 of those who take pleasure in study and reflection ; 

 and to those also the distinction between plants 

 and animals should be at least intelligible. The 

 wonderful power which plants exercise in building 

 up their tissues from carbonic acid, water, and 

 nitrogen, contrasted with the powerlessness of 

 animals to utilise these building materials until 

 they have been already assembled by plants, is a 

 phenomenon too fundamental and illuminating to 

 be w^ithheld, as it now is, from all but the few. 

 For by its operation the delicate green carpet, 

 which we all delight in following through the 

 annual process of covering the fields with golden 

 corn, is accomplishing throughout the summer 

 months a vast chemical synthesis of starch for 

 our benefit. .Through the tiny pores in those 

 tender blades are circulating freely the gases of 

 the atmosphere, and from those gases — ^light, in- 

 tangible nothingness, as we are prone to regard 

 them — this very tangible and important white 

 solid compound is being elaborated. The chemist 

 cannot do this. Plants accomplish it by their most 

 conspicuous feature, greenness, which enables 

 them to put solar energy into cold storage ; they 

 are accumulating fuel for subsequent development 

 of bodily heat energy. Side by side with starch, 

 however, these unadvertised silent chemical 

 agencies elaborate molecules even more imposing, 

 in which nitrogen is interwoven with the elements 

 of starch, and thus are produced the vegetable 

 alkaloids. 



In this province the chemist has been more for- 

 tunate, and successive generations of students 

 have been instructed in the synthesis of piperine, 

 coniine, trigonelline, nicotine, and extensions from 

 the artificial production of tropine ; but until quite 

 recently his methods have been hopelessly diver- 

 gent from those of the plant. Enlightening in- 

 sight into these, however, was given just four 

 years ago by R. Robinson, who effected a remark- 

 ably simple synthesis of tropinone by the mere 

 association of succindialdehyde, methylamine, and 

 acetone in water, unassisted by a condensing 

 agent or an increase of temperature. Based upon 

 this experiment, R. Robinson (1917) has developed 

 an attractive explanation of the phytochemical 

 synthesis of alkaloids, in which the genesis of a 

 pyrrolidine, piperidine, quinunuclidine, or iso- 

 quinoline group is shown to be capable of pro- 

 ceeding from the association and interaction of an 

 amino-acid, formaldehyde, acetonedicarboxylic 

 acid and the intermediate products of these, taking 

 place under the influence of oxidation, reduction, 

 and condensation such as the plant is known to 

 effect. Thus it may be claimed that Robinson's 

 theory represents a notable advance in our con- 

 ception of these vital changes, and that by 

 means of the carbinolamine and aldol con- 

 densations involved fruitful inquiries into con- 

 stitution and the mechanism of synthesis will 

 follow. 



NO. 2712, VOL. 108] 



The Nucleic Acids. 



Owing to the venerable position occupied by 

 alkaloids in the systematic development of chem- 

 ical science, and to the success which has attended 

 elucidation of their structure, many of us have 

 become callous to the perpetual mystery of their 

 elaboration. Those who seek fresh wonders, how- 

 ever, need only turn to the nucleic acids in order 

 to satisfy their curiosity. For in the nucleic acid 

 of yeast the chemist finds a definite entity form- 

 ing a landmark in the path of metabolic pro- 

 cedure, a connecting link between the undefined 

 molecules of living protein and the crystallisable 

 products of katabolic disintegration. In the lan- 

 guage of chemistry it is a combination of four 

 nucleotides, linked with one another through the 

 pentose molecule, d-ribose, which is common to 

 each, and owing its acid character to phosphoric 

 acid, also common to the component nucleotides. 

 The latter differ from one another in respect of 

 their nitrogenous factors, which are guanine 

 (2-amino-6-oxypurine), adenine (6-aminopurine), 

 uracil (2 : 6-dioxypyrimidine), and cytosine (2-oxy- 

 6-aminopyrimidine), giving their names to the 

 four nucleotides. The transformations undergone 

 by nucleic acid in contact with tissue extracts have 

 provided the subjects of numerous investigations 

 extending over thirty years. In fact, the experi- 

 mental material is of such voluminous complexity 

 as to be unintelligible without the guidance of an 

 expert, and in this capacity W. Jones has rendered 

 valuable service by his recent lucid arrangement 

 of the subject (192 1). From this it is compara- 

 tively easy to follow the conversion of nucleic acid 

 into uric acid through the agency of enzymes, and 

 a review of these processes can serve only to 

 increase our admiration for the precision and 

 facility with which the chemical operations of the 

 living body are conducted. 



Considerable progress has been made also in 

 localising the various enzymes among the organs 

 of the body, particularly those of animals. Into 

 the results of these inquiries it is not the purpose 

 of this address to enter further than to indicate 

 that they reveal a marvellous distribution, 

 throughout the organism, of materials able to 

 exert at the proper moment those chemical activi- 

 ties appropriate to the changes which they are 

 required to effect. The contemplation of such a 

 system continuously, and in health unerringly, 

 completing a series of chemical changes so 

 numerous and so diverse must produce in every 

 thoughtful mind a sensation of humble amaze- 

 ment. The aspect of this miraculous organisation 

 which requires most to be emphasised, however, 

 is that an appreciation of its complex beauty can 

 be gained only by those to whom at least the 

 elements of a training in chemistry have been 

 vouchsafed. Such training has potential .value^ 

 from an ethical standpoint, for chemistry is sl 

 drastic leveller; in the nucleic acids man discovers' 

 a kinship with yeast-cells, and in their common 

 failure to transform uric acid into allantoin he 

 finds a fresh bond of sympathy with apes. The 



