Observations on reputed dysentery remedies / by T.A. Genry and H.C. Brown.

  • Thomas Anderson Henry
Date:
[1924]
Catalogue details

Licence: Public Domain Mark

Credit: Observations on reputed dysentery remedies / by T.A. Genry and H.C. Brown. Source: Wellcome Collection.

    5/12 (page 380)
    It seems clear, therefore, that the toxic substance is included in the components precipitated by lead acetate. The materials removed by lead acetate from such plant extracts are usually gums, tannins, colouring matter and acids, and of these the only substances likely to possess protozoocidal properties are the tannins. It is interesting to note in this connection that many of the drugs which have been used for the treatment of unspecified dysenteries are rich in tannin, and it has been assumed generally that such drugs owe their value merely to their astringency and not to any toxic action of the tannins on the parasites. In view of these results it was considered advisable to try the action of a number of pure tannins on Glaucoma. Unfortunately, the chemistry of the tannins has not yet made much progress, and though these products can be isolated fairly easily from plants, it is usually not possible to say whether the material obtained is a single substance or a mixture of various tannins. Only one tannin, that of galls (gallotannin) is readily obtainable commercially in a pure state, but a number of substances, which are known to be closely related to the tannins, have been obtained crystalline, and there can be no doubt as to their purity. Among these are ellagic acid, chebulinic acid* (from myrabolans), catechin (from Gambier catechu), and acer tannin*. These five pure products have been tried, and, in addition, the authors have isolated, by the following process, the tannins present in a number of well-known tanning materials and astringent drugs :— The finely-ground plant was extracted with boiling light petroleum to remove wax and resin ; and then with boiling dry ether, which in some cases removed a little more resin. The residue was next extracted with boiling acetone. Where the tannin was removable with difficulty by acetone, ethyl acetate was used, and where this failed absolute alcohol was employed. The solvent was distilled from the extract in vacuo, the residue dissolved in water, the solution filtered and then precipitated (fractionally, if necessary, to remove colouring matter) with lead acetate. The lead acetate precipitate was de-leaded by suspension in water and passage of sulphuretted hydrogen, and the filtrate from the lead sulphide concentrated in vacuo to a thick syrup, absorbed in sawdust, which had been extracted previously with solvents to remove all soluble matter, dried thoroughly by heating below 100 in vacuo, and then re-extracted with dry ether to remove any traces of tat or resin left, and finally with acetone, ethyl acetate or absolute alcohol. I his treatment was repeated if necessary until a product, completely soluble in water or alcohol and giving all the reactions of tannins and Iree from gum, so far as could be judged by the application of tests,‘was obtained. Solutions of definite strength of the tannins in water were then made, and their action on Glaucoma determined by the method already described. The results are summarised in the following table :— * For specimens of these two substances the authors are much indebted to I r<d. A. G. i hi;kin. F.R.S.. of Leeds University.