XI] PLANT BASES 179 



The opium alkaloids again fall into two classes: (1) the papaverine 

 group which includes papaverine, laudanosine, narceine, narcotine 

 and others, and (2) the morphine group including morphine, apomor- 

 phine, codeine, thebaine and others. 



Opium is the dried latex obtained by making incisions in the cap- 

 sules of the Opium Poppy (Papaver somniferum). 



Allied to the papaverine group is hydrastine which occurs in the 

 root of Hydrastis canadensis (Ranunculaceae). 



The constitution of all these alkaloids is very complex. 



^^^^.163. Tests for morphine. 



(a) Add a little ferric chloride solution to a solution of a morphine salt. A deep 

 blue coloration is formed. 



(6) Dissolve some morphine in concentrated sulphuric acid and then after 

 standing about 15 hrs. add concentrated nitric acid. A deep blue-violet colour is 

 produced which afterwards changes to red. 



Berberine occurs in the root of the Barberry (Berberis vidgaris) and 

 is also found in isolated genera in Anonaceae, Menispermaceae, Papa- 

 veraceae, Ranunculaceae and Rutaceae. 



Corydaline occurs in Gorydalis cava (Fumariaceae). 



Many other alkaloid substances have been isolated from a large 

 number of different plants, but since the constitution of most of them 

 is unknown, they have not been classified. 



Purine and Pyrimidine Bases. 



These substances, as indicated (p. 3), have a hecterocyclic ring 

 structure and are derivatives of purine and pyrimidine: the atoms of the 

 ring are numbered in the order indicated below: 



N=:CH 



I I 

 HC C— NH IN— «C N==CH 



CH 2q 5Q_7f^ HQ Q„ 



^ i II V II II 



N— C— N 3N_4c_9N^ N — CH 



Purine Pyrimidine 



Purine itself is a crystalline basic compound (m. p. 211-212° C.) 

 which forms salts with acids. It is composed of two rings, the pyrimi- 

 dine and the iminazole: the latter grouping also occurs in histidine 

 (see p. 135). 



The chief purine bases which occur in plants are xanthine, guanine, 

 hypoxanthine, adenine, caffeine and theobromine. 



12—2 



