Pinckneya pubens, Michaux. (Georgia Bark.)
Natural order, Rubiaceae; sub-order, Cinchoneae.
By EDGAR HERMAN, NAUDAIN PH.G.
From an Inaugural Essay.
Michaux discovered this plant in 1791, along the banks of the St. Mary's River, Florida, and described it as follows: It grows in bogs along the banks of streams from Florida to South Carolina, near the coast, sometimes attains a height of twenty feet, though as it throws up many stems from the same root, it retains a shrub-like appearance. It has the general botanical characteristics of the Rubiaceae, the leaves are large, oval, and acute; downy on the under surface as are the flower-clusters which are borne at the end of the branches. These consist of several five-flowered fascicles of purplish spotted flowers. Calyx short, three-lobed, one of the lobes being expanded into a large ovate rose-colored leaf, which is more showy than the flower itself.
The plant is closely related to the cinchonae, and is one of the many that have been proposed as a substitute for Peruvian bark. From reports of physicians living in States where it grows, it appears to have decided anti-periodic properties, though slower in its action than cinchona bark. The genus was named in honor of Gen. Charles Pinckney, of South Carolina.
Considerable difficulty was experienced in securing a sample of the bark, but through the kindness of Mr. G. J. Luhn, of Charleston, South Carolina, a small quantity was obtained, together with several leaves and a cluster of fruit. The bark was in quills about two inches in length, from 1/16 to 1/8 inch in thickness; externally of an ash gray color, and somewhat warty; internally brownish white, of a distinctly bitter taste, and breaking with a short corky fracture.
A portion of the bark was exhausted by repeated digestion, with water acidulated with hydrochloric acid; but the acid infusion failed to give any reaction for alkaloids when tested with Mayer's test, picric acid, or phospho-molybdic acid. On concentrating a portion of this solution numerous crystals separated; they were boiled with a solution of sodium carbonate and filtered, the filtrate neutralized gave a precipitate with calcium chloride indicating oxalic acid. The insoluble residue was dissolved in acetic acid and tested with ammonium oxalate with which it gave a precipitate indicating- that the crystals were calcium oxalate.
Seventy-five grams of the bark in very fine powder were submitted to the action of petroleum benzin (which had previously been redistilled) until it was thoroughly exhausted. On distilling off the benzin a greenish, wax-like substance remained; this was treated with acidulated water (HCl), to which it yielded nothing, giving no reactions when tested for alkaloids. It was next treated with eighty per cent. alcohol, which extracted a small quantity of a yellow resinous body, soluble in ether. The residue consisted of a waxy substance associated with a small amount of chlorophyll. Fixed and volatile oils were found to be absent.
Alcoholic Extract.—The powdered bark from the benzin operation was kept at a temperature of 100° C. until all traces of benzin bad disappeared, was then thoroughly exhausted with eighty per cent. alcohol and the tincture distilled; the concentrated liquid was precipitated by an alcoholic solution of normal lead acetate, and the filtrate freed from lead by hydrogen sulphide concentrated and allowed to stand, nothing separating out; on dilution with water a slight precipitate was formed, which on agitating with ether was dissolved, and on evaporation yielded a dark brown resinous body of a slight taste, and soluble in chloroform and bisulphide of carbon.
The aqueous extract failed to give any reaction for alkaloids when tested with picric acid, phospho-molybdic acid and Mayer's test. The remaining aqueous liquid was precipitated by triplumbic, acetate, the filtrate was again freed from lead by hydrogen sulphide and concentrated; on allowing it to stand a light brown, distinctly crystalline substance was deposited, weighing about 0.15 grm., having a very bitter taste similar to that of the bark very much concentrated. It failed to reduce Fehling's solution until boiled with dilute sulphuric acid, and it was entirely dissipated by heat. The substance is a glucoside, I think, and I propose for it the name Pinckneyin. The precipitate by the triplumbic acetate was suspended in water and freed from lead; on evaporating, a brownish, somewhat bitter extractive was obtained.
The plumbic acetate precipitate was suspended in eighty per cent. alcohol, freed from lead by hydrogen sulphide, concentrated, treated with water, allowed to stand some time, and the resulting precipitate collected, well washed and dissolved in ether, which left on evaporation a light yellow mass, capable of being powdered; its alcoholic solution was very astringent, and was precipitated, giving a bluish green by ferric chloride. The aqueous solution gave, with ferric chloride, a beautiful emerald green color, changed to a wine red by sodium carbonate, was not precipitated by tartar emetic, not precipitated or colored by ferrous sulphate, reduced solution of argentic nitrate, was precipitated by gelatin, and crystallized from dilute alcohol, resembling caffeotannic acid.
Aqueous Extract.—The bark from the alcohol operation was macerated with water and expressed, the liquid gave a copious precipitate with alcohol, which consisted of gum combined with brown coloring matter. On boiling a portion of the exhausted bark with water, the solution gave a blue coloration after cooling with a solution of iodine. One grm. of the bark (air-dry?) on incineration yielded .09 grm. = 9 per cent. of ash, consisting of potassium, sodium, calcium and magnesium combined as chlorides, carbonates and phosphates.
In the "American Journal Pharmacy," February 1881, p. 98, it is stated that Dr. Farr claimed to have detected cinchonine in pinckneya, but from my analysis I am led to think this incorrect, as I failed to discover the slightest trace of alkaloid. Owing to the limited supply of bark at my disposal I was unable to make as complete an analysis as the subject deserves.