Digitonin is a glycoside obtained from Digitalis purpurea; the aglycone is digitogenin, a spirostan steroid. Used as a detergent, it effectively water-solubilizes lipids. As such, it has several membrane-related applications in biochemistry, including solubilizing membrane proteins, precipitating cholesterol, and permeabilizing cell membranes. Digitonin is sometimes confused with the cardiac drug digoxin, but has no heart-related effects. Phlebotonic drugs are very often old drugs which improve symptoms in chronic venous insufficiency but their precise mechanism remains unclear. One hypothesis which is being more and more substantiated is that the origin of the disease lies in the activation of the endothelium during blood stasis, leading to a cascade of reactions which, in the long term, alter the structure of the vein wall.