saponin 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.

saponin Any member of a class of glycosides that form colloidal (see COLLOID) solutions in water and foam when shaken. Saponins have a bitter taste, hydrolyse (see HYDROLYSIS) red blood cells, and are very toxic to fish. They occur in a wide variety of plants, including Saponaria officinalis (soapwort), which produces a lathery liquid, once widely used for washing wool and still used for delicate textiles, including antique ones.

sap·o·nin / ˈsapənən/ • n. Chem. a toxic compound that is present in soapwort and makes foam when shaken with water. ∎  any of the class of steroid and terpenoid glycosides typified by this, examples of which are used in detergents and foam fire extinguishers.

saponin Any member of a class of glycosides that form colloidal solutions in water and foam when shaken. Saponins have a bitter taste, hydrolyse red blood cells, and are very toxic to fish. They occur in a wide variety of plants, including Saponaria officinalis (soapwort), which produces a lathery liquid, once widely used for washing wool and still used for delicate textiles, including antique ones.