This section is from the book "Botanic Drugs Their Materia Medica, Pharmacology and Therapeutics", by Thomas S. Blair. Also available from Amazon: Botanic Drugs, Their Materia Medica, Pharmacology and Therapeutics.
Buckthorn, Rhamnus frangula. Very generally official; the bark in the U. S. and many other countries, the berries in France and Belgium. Like cascara, the bark should be collected one year before using so as to lose its acrid and emetic properties. A purgative of the anthracene group, containing emodin and chrysophanic acid.
Some years ago a prominent authority said: "There is little reason for considering it (cascara) as essentially different from or more valuable than frangula bark or common buckthorn, and hence its popularity, being forced and fictitious, will be shortlived." How fallible authorities are! Now, as a matter of fact, both R. purshiana and R. frangula, when fresh, are harsh and violent in action; but a year's curing of the bark removes these harsh properties. Frangula should be more popular; it is very closely allied to cascara. The old "Surgeon's Tea" was a decoction of frangula and uvaursi. It was used preparatory to operation and during the lying-in period. It is really useful, especially in the transient albuminuria of pregnancy. Use average doses of the crude drugs in making the decoction. Dose: Frangula fl., 10 to 30 minims. Valuable in chronic constipation. Indications the same as cascara.