1. Fruits of Capsicum fastigiatum—These are ½ to ¾ of an inch in length, by about ²/₁₀ of an inch in diameter, of an elongated, subconical form, tapering to a blunt point, and slightly contracted towards the base. The calyx, which is not always present, is cup-shaped, 5-toothed, 5-sided, supported on a slender, straight pedicel, ¾ to 1 inch long. The fruits, which are somewhat compressed and shrivelled by drying, and also brittle when old, have a leathery, smooth, shining translucent, thin, dry pericarp, of a dull orange-red, enclosing about 18 seeds, attached in two cells to a thin central partition. The seeds have the form of roundish or ovate discs, about ⅛ of an inch in diameter, somewhat thickened at the edges; the embryo is curved, almost into a ring. The taste of the pericarp, and likewise of the seeds, is extremely pungent and fiery. The dried fruit has an odour by no means feeble, which we cannot compare to that of any other substance.
2. Fruits of Capsicum annuum of the commonest variety resemble those of C. fastigiatum, except that they are of longer size, being from 2 to 3 or more inches in length, often rather more tapering towards the extremity. The seeds scarcely surpass in size those of C. fastigiatum.
Microscopic Structure—The pericarp consists of two layers, the outer being composed of yellow thick-walled cells. The inner layer is twice as broad and exhibits a soft shrunken parenchyme, traversed by thin fibro-vascular bundles. The cells of the outer layer especially are the seat of the fine granular colouring matter. If it is removed by an alcoholic solution of potash, a cell-nucleus and drops of fat oil make their appearance. The structural details of this fruit afford interesting subjects for microscopical investigation.
Chemical Composition—Bucholz in 1816, and about the same time Braconnot, traced the acridity of capsicum to a substance called Capsicin. It is obtained by treating the alcoholic extract of ether, and is a thick yellowish-red liquid, but slightly soluble in water. When gently heated, it becomes very fluid, and at a higher temperature is dissipated in fumes which are extremely irritating to respiration. It is evidently a mixed substance, consisting of resinous and fatty matters.
Felletár in 1869 exhausted capsicum fruits with dilute sulphuric acid, and distilled the decoction with potash. The distillate, which was strongly alkaline and smelt like conine, was saturated with sulphuric acid, evaporated to dryness, and exhausted with absolute alcohol. The solution, after evaporation of the alcohol, was treated with potash, and yielded by distillation a volatile alkaloid having the odour of conine.
From experiments made by one of us (F.) we can fully confirm the observations of Felletár. We have obtained the volatile base in question, and find it to have the smell of conine. It occurs both in the pericarp and in the seeds, but in so small proportion that we were unsuccessful in isolating it in sufficient quantity to allow of accurate examination.
Dragendorff states (1871) that petroleum ether is the best solvent for the alkaloid of capsicum; he obtained crystals of its hydrochlorate, the aqueous solution of which was precipitated by most of the usual tests, but not by tannic acid.
The colouring matter of capsicum fruits is sparingly soluble in alcohol, but readily in chloroform. After evaporation, an intensely red soft mass is obtained, which is not much altered by potash; it turns first blue, then black with concentrated sulphuric acid, like many other yellow colouring substances. By alcohol chiefly palmitic acid is extracted from the fruit, as shown by Thresh in 1877.
The fruits of Capsicum fastigiatum have a somewhat strong odour; on distilling consecutively two quantities, each of 50 lb., we obtained a scanty amount of flocculent fatty matter, which possesses an odour suggestive of parsley. Both this matter, as well as the distilled water, were neutral to litmus paper, and the water tasteless. We separated the latter, and exposed the remaining greasy mass to a temperature of about 50° C., when it for the most part melted. The clear liquid on cooling solidified, and now consisted of tufted crystals, which we further purified by recrystallization from alcohol. Thus about 2 centigrammes were obtained of a neutral white stearoptene, having a decidedly aromatic, not very persistent taste, by no means acrid, but rather like that of the essential oil of parsley. The crystals melted at 38° C. On keeping them for some days at the temperature of the water-bath, covered with a watch-glass, some drops of essential oil were volatilized, which had the same taste and did not solidify; the crystals were consequently accompanied by a liquid oil. When kept for some days more in that condition, the crystals themselves began to be volatilized, and the part remaining behind acquired a brownish hue. This no doubt points out another impurity, as we ascertained by the following experiment. With boiling solution of potash, the stearoptene produces a kind of soap, which on cooling yields a transparent jelly. If this is dissolved and diluted, it becomes turbid by addition of an acid. This probably depends upon the presence of a little fatty matter, a suggestion which is confirmed by the somewhat offensive smell given off by our stearoptene if it is heated in a glass tube.
Buchheim’s “Capsicol”[1665] is in our opinion a doubtful substance.