Leucomaines.[13]
The leucomaines are basic substances, nearly allied to the ptomaines, but still more closely related to the ureides. They are formed directly or indirectly by the breaking down of protoplasmal albuminoids. The agents that effect the breaking down are the hydrolyzing ferments of the economy. It is well to recall here that these phenomena of hydrolyzation occur within the cell itself and in a practically reducing medium, as we have already stated. The inmost mechanism of these phenomena cannot here be detailed; it will be found described by Armand Gautier in the Chimie Biologique, and in his work Chimie de la Cellule Vivante.[14]
The extraction of these bases is an extremely delicate operation. It is necessary to operate with a large quantity of substance, say 50 kilos. The substance is finely chopped, then exhausted with twice its weight of water acidulated with acetic acid (0.2 Cc. per liter) and containing a trace of oil of mustard, which is intended to act as an antiseptic. The albuminoids are precipitated by boiling, the solution then filtered, evaporated in a vacuum at 60° C., and the bases extracted with 95-per cent. alcohol.
The alkaloidal bases obtained in this manner are separated by crystallization from alcohol or by various other chemical methods, the description of which we will not enter upon here.
In order to facilitate the study of the leucomaines they are classed under three groups, according to their chemical affinities. These groups are as follows:
1. Xanthic Leucomaines.—The bases of this group appear to have a composition resembling that of uric acid. When hydrolyzed, they yield urea and guanidine. They are weak bases, and exhibit both basic and weakly acid properties. They all possess the common characteristic of being precipitated by copper acetate in acid solution with heat, and by ammoniacal silver nitrate in the cold.
According to Kossel, these bases are derived from the nucleo-albumins which are found in the cell nuclei, and which are, as we know, substances rich in nitrogen and phosphorus.
Among the bases of this group may be mentioned adenine, C5H5N5, which is obtained from infusions of tea.[15] This base is non-toxic; it was discovered by Kossel,[16] and it crystallizes easily.
Some others of this group are:
Guanine, C5H5N5O, non-toxic, discovered by Unger; pseudo-xanthine, obtained from muscular tissues; sarcine, C5H4N4O, also but slightly toxic, discovered by Scherer; xanthine, C5H4N4O2, which is found in many urines, and which acts as a stimulant on the cardiac muscles; paraxanthine, C7H8N4O2, a toxic base found in certain pathological urines; caffeine and theobromine, powerful diuretic bases; and carnine, C7H8N4O3, from meat, a muscular stimulant like caffeine.