False and True Senega.
BY GEO. GOEBEL, JR.
From an Inaugural Essay.
A root designated as "Southern Senega" has been lately introduced and sold in place of true senega. (This has since be identified as Polygala alba...weaker than the official plant, but quite serviceable. I have been using it for years.—MM) As Polygala senega is one of the most valuable American drugs, it is of great importance that it should not be displaced by a new variety without a knowledge of its medicinal properties and constituents, as compared with the true senega; therefore the writer has undertaken a comparative microscopic and physical examination of the two varieties, with a chemical analysis of the medicinal constituent.
The false senega as met with in commerce is a root varying from a yellow to a lightish brown color, surmounted by a knotty head or crown of from a half to three-fourths of an inch in diameter, the knotty crown displaying numerous stem scars. Below this crown is found the root proper, which is from three to six inches in lengthy irregularly branched, cylindrical, tapering, longitudinally wrinkled, and breaks with a short fracture, displaying a brittle and readily removable bark, which constitutes about one-fifth of the bulk of the root. It is difficult to reduce to a fine powder on account of the hardness of the woody portion, the powder being sternutatory and of a very light straw color. The drug when masticated causes coughing; and a painful sensation in the fauces.
All efforts to trace its exact habitat, or procure a plant, so far, have-proven fruitless; the only information that could be elicited was that it came from the Southern States.
Greenish, in 1878, described a Polygala which corresponds with this false senega, and, after having made a histological examination, pronounced it true senega, but young and immature. This statement of Greenish is erroneous, as all true senega, whether young or old, has the characteristic keel-like projection and the irregularly formed woody tissue.
The true senega is of from a light to a dark brown color, surmounted by a very knotty head or crown of from a half to one and a quarter inch in diameter. The root proper is of from one-eighth to three-eighths inch in diameter at the upper part, is branched and tapering, of from two to five inches in length, and very much contorted, with a projecting, keel-like ridge, running the entire length of the root and rootlets in a spiral form. It is both longitudinally and transversely wrinkled, breaks with a short fracture, and exhibits a somewhat porous, rather firmly adhering bark, which varies in thickness of from one-third to one-fifth of the thickness of the root. The projecting keel disappears upon being boiled with water, and reappears when the root is dried. The woody portion is from a light yellow to almost a white color, and is in different places very irregular in shape, owing to a non-formation of portions of the woody tissue. The root is capable of being reduced to fine powder with greater ease than the false variety, the dust being very sternutatory; when chewed it produces a painful sensation in the throat and excites coughing.
The false senega, when cut transversely, exhibits an outer layer of cells, rather irregular, very compact, thin and corky; the inner bark is about five or six times as thick, its cells are very regular and appear in distinct circles, varying in size; the outer circle is formed of very small, flattened cells; the second, broader layer, consists of oval cells, and is followed by a zone of smaller slightly flattened cells, and by an inner circle of cells, nearly similar to the preceding. A very thin cambium layer separates the bark from the wood, which is rather compact, with slightly curved numerous medullary rays, composed of small flat parenchyma cells; the woody cells are small, somewhat oval shaped, intermixed with larger ducts, of the same shape, arranged in three distinct circles.
In longitudinal section, the corky layer of the bark is rather irregular; in the next layer the cells are long and flattened, followed by somewhat larger oval cells, and then by long, flattened, very compact liber cells, and finally by shred-like, very compact cells, and by the thin cambium. The wood is composed of prosenchyma tissue, with large ducts.
The true senega, when transversely cut, exhibits a bark with a very thin corky layer, and consists of hexagonal cells, forming three layers, the cells of the inner layer being much smaller in size. Inside of the thin cambium layer is the radiating woody portion, composed of wood cells and hexagonal ducts, arranged in straight lines, occasionally in pairs, and about four times as large as the adjoining cells.
In the longitudinal section are seen the thin corky layer, the somewhat loose-celled middle bark, the dense inner bark containing elongated cells, the thin cambium, and the compact wood with large ducts.
Polygalic acid, being the active constituent in senega, the writer's experiments have been chiefly directed to the elimination of that principle in the two drugs.
Ten troyounces of the false senega were treated as directed by Procter, in the "American Journal of Pharmacy," 1860, page 150. The powder was exhausted by percolation with a mixture of two parts of alcohol and one of water until the percolate was free from taste and ceased to give a precipitate with basic acetate of lead. This percolate was evaporated by a water-bath to three fluidounces. During the evaporation, when the liquid reached the temperature of 158°F., it became opaque, and at 167°F. a flocculent precipitate was produced, which was filtered off, and it appeared to be albuminoid. The evaporated liquid was repeatedly shaken with fresh portions of ether, until the latter ceased to acquire color. This required fourteen fluidounces. The syrupy liquid remaining was mixed with twelve fluidounces of alcohol, and four fluidounces of ether to precipitate the polygalic acid,. which is insoluble in this menstruum. The precipitate so formed was filtered off, and proven when treated with Fehling's solution to be glucose, the polygalic acid remaining in solution.
Another portion of the drug was treated by a modification of Quevenne's process; it was exhausted, first with stronger alcohol, the percolate evaporated to three fluidounces, and mixed with an equal bulk of distilled water; a light yellow precipitate of a resinous character was produced, which when filtered from the solution was found to be soluble in ether, stronger alcohol and solution of potassa. The remaining liquid was treated with solution of basic acetate of lead until a precipitate ceased to be produced; the precipitate so formed was filtered off, suspended in distilled water, and decomposed by hydro-sulphuric acid; the filtered liquid was evaporated by means of a water-bath, when the polygalic acid remained as a brownish powder; it was then well shaken with ether, to remove adhering coloring matter; the ether was decanted, leaving the polygalic acid as an amorphous light yellowish powder. The amount of acid thus obtained was two per cent.
The remaining drug was now treated with dilute alcohol until two pints had passed; this was evaporated to four fluidounces, precipitated with solution of basic acetate of lead, the precipitate filtered off, suspended in water and decomposed by sulphuretted hydrogen, (The sulphide of lead is stated by Quevenne to retain a portion of the polygalic acid, and on that account requires to be treated with hot alcohols —EDITOR.) and the filtered liquid evaporated to dryness, leaving polygalic acid to the extent of one per cent., making a total of three per cent. of polygalic-acid in this false senega.
Procter's process, when applied to true senega, yielded five per cent. of acid, while Quevenne's process gave five and a quarter per cent. Procter's process, being less complicated, is preferable for the manufacture of polygalic acid from true senega.
Polygalic acid so obtained is somewhat contaminated with glucose, from which it is very difficult to separate on account of their similar solubilities. Polygalic acid is insoluble in ether, chloroform, slightly soluble in alcohol, soluble in dilute alcohol and water, also in boiling alcohol, but separates to some extent upon cooling. Besides the acid, both drugs were found to contain, in varied quantities, tannin, glucose, pectin compounds and resin.
The pharmaceutical preparations made from the two roots were as follows:
|Preparation.||From false senega.||From true senega.|
|Decoction, U. S. P.||Light straw color; weak senega odor; nearly insipid.||Deep straw color; strong odor and taste of senega.|
|Infusion, Br. P.||Like preceding.||Similar to preceding.|
|Fluid extract, U. S. P.||Transparent, dark sherry color; senega odor, somewhat modified.||Dark brown; odor nauseous; taste sweetish, then strongly acrid; excites coughing.|
|Syrup, U. S. P.||Yellowish-brown; slight odor and taste of senega.||Deep brown or wine color; senega odor and taste prominent.|
|Comp. Syrup, U. S. P.||Light yellowish-brown; slight odor and taste of senega.||Reddish-brown; odor and taste of senega well marked.|
|Tincture, Br. P.||Light golden-yellow; odor and taste of senega prominent.||Dark golden-yellow; strong senega odor, and characteristic taste.|
The preparations of the true senega required the following amounts of diluents to obtain a color corresponding with that of the same preparation of the false root: decoction, 36 per cent. water; infusion, 40 per cent. water; fluid extract, 40 per cent. alcohol; syrup and compound syrup, 34 per cent. syrup; tincture, 30 per cent. alcohol and water.