A Chemical Examination of Polygonum hydropiper.

Botanical name: 


(A contribution from the Chemical Laboratory of the Philadelphia, College of Pharmacy)

From recent reports of the medicinal activity of this drug and from the absence of a complete analysis of it, we were induced to undertake an examination with a view, primarily, of determining the nature of the pungent principle. The drug was collected for us in the vicinity of Philadelphia, during the past summer, by a botanist thoroughly familiar with the requirements of the case, so there can be no doubt about the species of Polygonum employed in the following analysis.

About 50 grams of the tops and leaves, free from the larger stems, were powdered and the whole passed through a No. 80 sieve; of this 20 grams were taken, and the scheme recommended in Dragendorff's Plant Analysis followed as closely as the peculiarities of the case would admit.

Petroleum spirit, with a boiling point below 45°C., extracted 2.7 per cent. of a material which proved to be a wax, melting at 48°C., soluble in absolute alcohol, ether and chloroform, and saponifying with alcoholic potash. No volatile or fixed oils were found.

The drug, after extraction with petroleum spirit, was dried and exhausted with absolute ether, which extracted 1.54 per cent., a very small portion of which was soluble in water, the remainder was soluble in chloroform, benzol and absolute alcohol; a concentrated solution in the last solvent, when poured into water caused a turbidity due to resin; from these and some other tests, we were led to believe that the ether-soluble portion consisted of resin and chlorophyll.

The original drug after the ether treatment was dried and exhausted with absolute alcohol, by which we obtained 5.14 per cent. of solid matter. 2.27 per cent. of this was soluble in water; this aqueous solution contained tannin. When made alkaline and treated successively with petroleum spirit, benzol and chloroform, then acidified and similarly treated, no crystalline principle was obtained. The portion of the alcoholic extract insoluble in water proved to be an acid resin. The alcoholic solution contained the pungent principle, but on heating it disappeared.

The remainder of the original drug yielded to water 7.22 per cent. of solid matter. No crystalline principle was found, but there was obtained .55 per cent. of gum and 1.44 per cent. of sugar. That portion of the drug insoluble in water yielded 5.95 per cent. of solid matter to a .2 per cent. solution of potassium hydrate, which was made up to 1 per cent. of albuminoids and some phlobaphene. That which remained from the treatment with dilute alkali gave to hydrochloric acid 6 per cent. of solid matter which consisted principally of the salts found in the ash. Only a very small amount of starch was found. On bleaching the final residue with chlorine water, drying and weighing, 57.45 per cent. of cellulose was obtained. Another portion of the original drug yielded 10.25 per cent. of moisture, and on incineration, 7.4 per cent. of ash of which 3 per cent. was soluble in water, consisting of potassium and sodium salts; the remainder proved to be iron, aluminium and calcium with phosphoric acid.

Two tannin determinations, by the gelatin and alum process, gave very close to 3.46 per cent. A tincture of the drug was made with diluted alcohol, which contained the pungent principle, but on concentrating by distillation that peculiar taste failed to show itself, either in the concentrated residue or in the distillate. The residue on treatment with petroleum spirit, benzol and chloroform, yielded nothing. From these experiments we concluded that the active principle is decomposed on the slightest heating, and that the only proper preparation of the drug would be one made without the application of beat.

In AMERICAN JOURNAL OF PHARMACY for November, 1871, Dr. C. J. Rademaker claims to have isolated the active principle, which be named polygonic acid. We prepared some of this substance according to his method, by exhausting the drug with diluted alcohol, evaporating and adding basic acetate of lead, by which we obtained the yellow precipitate. This, on treatment with H2S, yielded to the first portions of ether shaken with it a greenish, and to the successive portions a brownish residue. All these portions were acid to litmus paper and gave the reactions stated by the author. We also found this residue to give a precipitate with gelatin, and in many other ways to resemble tannic as well as gallic acid; the latter would account for the crystal-line appearance of the residue. As such treatment of the drug would probably give tannic and gallic acids, we tried a mixture of the two by the same reagents as were applied to the so-called polygonic acid, and found a remarkable similarity. The conclusion naturally follows that polygonic acid is a mixture of impure tannic and gallic acids, together with a small quantity of chlorophyll.

The following summary shows the amount of the most important constituents:

Per cent.
Water 10.25
Wax 2.70 From petroleum spirit solution
Resin and chlorophyll 1.54 From ether solution
Resin, tannin and chlorophyll 5.14 From alcoholic solution
Sugar 1.44 From aqueous solution
Gum .55
Tannin and extractive 5.23
Albuminoids 1.00 From alkali solution
Phlobaphene, etc. 5.95
Salts and a small amount of extractive 6.00 From dilute acid solution
Cellulose 57.45
Total 97.25

Separately determined: tannin, 3.46 per cent.; ash, 7.40 per cent.

PHILADELPHIA, December 16, 1884.

The American Journal of Pharmacy, Vol. 57, 1885, was edited by John M. Maisch.