1 6 PASTORAL AND AGRICULTURAL BOTANY 



CHEMICAL NATURE OF POISONING 



The modern chemical investigation of poisonous plants has resulted 

 in the isolation of the active principles of many plants which have been 

 determined to be nitrogenous substances of basic character, and to this 

 class of substance the name of alkaloid has been given. It has been found 

 also that all poisonous plants do not contain alkaloids, but in addition 

 there are non-alkaloidal active principles, which include a large number 

 of different types of chemical compounds, including the substances known 

 as glucosides, which are readily hydrolyzed by dilute acids, or by ferments 

 into a sugar and another constituent, which is generally physiologically 

 active. The isolation of the active compounds has been of importance in 

 determining the strength of the dosage of the drug, which could be safely 

 administered to animals. The study of these actively poisonous substances 

 led to various attempts at their production synthetically. Chemists 

 owing to the backward condition of their science were unable to produce 

 the complex active substances, but their study has led to the discovery 

 of the portion of the molecule which produces the physiological effect 

 and this has led to the discovery of simpler analogous compounds possessing 

 the action of the drug, or poison. 



The discovery was made that the physiological action of the drug, or 

 poison, was dependent in general on its chemical nature, although modified 

 naturally by differences in physical properties such as solubility, volatility 

 and the like. Thus, a very small change in the chemical constitution of a 

 poison, is often accompanied by a complete change in its physiological 

 action. There is often a great difference in the activity of stereo-isom- 

 erides. In the case of optically active stereo-isomerides, we find marked 

 differences in their physiological action. For example, atropin (racemic 

 hyoscyamin) differs in some respects from /<CT0-hyoscyamin, and l&vo- 

 nicotin is twice as actively poisonous as the dextro-v&nety. Adrenalin 

 is a striking example, the natural Icevo form being about eleven, or twelve 

 times as active as the dextro. J9e#/r0-asparagin is sweet. Zt>0-aspara- 

 gin is tasteless. Unsaturated compounds are usually far more toxic 

 than the corresponding saturated ones. Propyl alcohol, CH2 CH 2 

 CH 2 OH, is a narcotic, causing intoxication, although not really poison- 

 ous, whereas allyl alcohol, CH 2 = CH CH 2 OH, is a strong poison, 

 although not having narcotic action. The influence of increasing un- 

 saturation is displayed in the graphic formulae below: from May's 

 "The Chemistry of Synthetic Drugs," page 32. 



