Any of a class of glycosides, found widely in plants, that have detergent properties and form a lather when shaken with water. They are especially concentrated in the soapwort (Saponaria officinalis), whose foliage was formerly boiled and used as a soap substitute. Chemically saponins consist of a sugar group (e.g. glucose) linked to a steroid or triterpene group; a related group of compounds, the sapogenins, have no sugar group. Their presence in plants is thought to act as a deterrent to herbivores – they are bitter-tasting and cause gastric irritation if ingested. They are also highly toxic to fish. If injected into the bloodstream they disrupt red cells, through their effects on plasma membranes.
Subjects: Biological Sciences.