This section is from the book "Materia Medica And Therapeutics: An Introduction to the National Treatment of Disease", by John Mitchell Bruce. Also available from Amazon: The pharmacology and therapeutics of the materia medica.
Quebracho Bark. (Not Officinal.)-The bark of Aspidosperma Quebracho. From Chili.
Characters.-In pieces, 3/4 inch thick; interior, fibrous and cinnamon-brown, with a short fracture; exterior, reddish ochre-coloured, warty; taste, bitter, slightly aromatic, unpleasant.
Composition. - Quebracho bark and wood contain an alkaloid, aspidospermin, C22H18N2O2 , soluble in spirit, nearly insoluble in water. The wood contains much tannin.
Non-officinal Preparations. Extract; Tincture (1 to 5) in doses of 6 min to 1 fl.dr.
Quebracho and aspidospermin reduce the frequency of respiration, through the centre; the heart's action through the intrinsic ganglia; the sense of dyspnoea induced by exercise; and the body temperature. The bark has been used with success in some cases of disease attended by dyspnoea, especially emphysema, but is an uncertain drug, and should be given with caution.