NOSCELLANEOUS NITROGEN AND SULFUR COMPOUNDS 



275 



densations occur both inter-and intra-molecularly. Thus, by decarboxylation methyla- 

 mine is derived from glycine, ethanolamine from serine, putrescine fronn ornithine, etc. 

 The methylamines may also be derived by an oxidative splitting of choline. The N-methyl 

 groups found in secondary and tertiary amines, or quaternary ammonium compounds like 

 choline, are derived from methionine and/ or formate. 



Of great pharmacological interest are the so-called pressor amines which show a 

 powerful effect on the blood pressure of animals. Many of these compounds are decar- 

 boxylation products of aromatic amino acids and histidine. They are found widely dis- 

 tributed in plants although usually in small amounts (2). In some cases, though, the 

 presence of pressor amines may account for the toxicity or pharmacodynamic effects of 

 certain plants. For example, tyramine is found in the poisonous berries of mistletoe 

 (Viscum album); histamine, serotonin, and acetylcholine in the hairs of stinging nettles 

 (Urtica spp. ); and ephedrine in the ancient Chinese drug plant ma-huang {Ephedra spp. ). 



Some amine structures are given in Table 1 which shows the amino acid from which 

 each is derived. The common names of corresponding N-methyl and quaternary ammoni- 

 um compounds (betaines) are given in the third column only If these are known as higher 

 plant constituents. Indole amines derived from tryptophan are discussed in a later sec- 

 tion. 



No generalization can be expected to describe the function of all amines in plants, 

 and for most of them even suggestions are lacking. Methylated compounds may serve as 

 reservoirs for methylation reactions. Choline has been the most widely investigated of 

 these compounds. It is a part of many phospholipids (q. v. ); its phosphoryl derivative 

 may function as an important phosphate carrier in plant sap (3): 



(CH3)3NCH2CH20P0 



OH 



After oxidation to glycinebetaine, choline can sometimes serve as a methyl donor (e. g. 

 in nicotine synthesis). Choline sulfate may function as a sulfur transporting agent and 

 reservoir (4). 



Isolation of the simple amines from plants takes advantages of their basic nature. 

 Thus, they may be separated on cation exchange resins. The more volatile ones may be 

 separated from plant materials by steam distillation from an alkaline mixture (after pre- 

 liminary removal of volatile neutral and acidic compounds). One danger to be recognized 

 is that many plants contain amine oxidases which must be promptly inactivated if amines 

 are to be preserved when cellular structure is broken down. Non-volatile amines can be 

 isolated by first removing proteins from the plant extract with heat, trichloracetic acid, 

 etc. and then precipitating the amines with various reagents. A reagent useful for pre- 

 cipitating amines from protein-free solutions is phosphotungstic acid in 5% H2SO4. Am- 

 monium and potassium ions should be removed since they are also precipitated by this 

 reagent. Several techniques are available for fractionating the phosphotungstate precipi- 

 tate and recovering free amines from it. Dragendorff's reagent (KBilj) and Reinecke's 

 salt (NH4Cr(NH3)2' SCN4- H2O) have been extensively used to precipitate the quaternary am- 

 monium bases (5, 6). 



Several simple tests are available for characterization of amines, in particular for 

 determining whether an unknown compound is a primary, secondary, or tertiary amine 

 or a quaternary ammonium base. Some of these tests may be effectively applied to paper 



