January 5, 1949
Doctor W. C. Deming 31 South Highland Street West Hartford, Connecticut
Dear Doctor Deming:
This is in reply to your inquiry of December 28, 1948, regarding the toxicity of horse chestnuts.
All six of the species of Aesculus which are native to the United States have been reported as poisonous, but specific references in the literature are infrequent. The species Aesculus hippocastanum has been studied and has been found to contain saponin, tannin, and the glycoside, esculin. Esculin is used in patent remedies in the form of ointments and pastes to protect the skin from sunburn. The saponin seems to be the toxic component.
Fruit of the horse chestnut is rich in starch and oil and is a valuable food for livestock. The bitter taste of the nut is removed by alcohol extraction which removes the saponin, thus rendering the nut harmless. Certain domestic animals, however, seem to be able to eat the untreated nut without suffering ill effects. [Italics are by Dr. Deming.—Ed.]
Most of the saponins are markedly irritant to the mucous membranes. They have an acrid taste and provoke a flow of saliva, nausea, vomiting and diarrhea. If injected directly into the circulation they produce hemolysis, diuresis and direct actions on the central nervous system which may be rapidly fatal. Absorption after oral administration is so poor that saponins produce only local effects. The toxicity of various saponins is ten to a thousand times higher by vein than by mouth and is generally proportional to the hemolytic action. Some saponins have a different toxicity for different species.
In experiments with rats Hindemith found that the saponin from Aesculus hippocastanum is not toxic in daily oral doses of 87.5 mg. per kg. Nonhemolytic doses injected intravenously in cats have no effect on respiration or blood pressure; hemolytic doses produce a sudden drop in pressure owing to liberation of potassium from the erythrocytes. The saponin increases the activity of the isolated frog heart, then stops it in systole. In frog nerve muscle preparations of this saponin reversibly interrupt stimulus transmission; recovery occurs upon washing.
For a general review of the literature you are referred to Bull. Sc.
Pharmacol. 47:290 (November-December) 1940, which is available at the
New York Academy of Medicine Library, 2 East 103rd Street, New York
City.
Sincerely yours,