Saponins normally break down in the digestive system and must enter the bloodstream to be toxic, but fish take in saponins directly into their bloodstream through their gills. The toxin acts on the respiratory organs of the fish without affecting their edibility. Saponins also cause the breakdown of red blood cells that help the toxin to spread quickly. Even though the effects of the poison are powerful, they are not usually fatal. Fish that are washed away into untainted water revive, and canreturn to their pre-toxic condition. Because of this, the fishermen would have to gather the stunned fish quickly as they floated to the surface.
Saponins are one of a group of glucosides found in many plant species with known foaming properties when mixed with water. Saponins lower the surface tension of water allowing the formation of small stable bubbles. The amount of foam created by a crushed plant sample, shaken with water in a jar, is a good indication of the amount of saponins present.
Saponins have been used in modern times in the manufacture of fire extinguisher foam, toothpaste, shampoos, liquid soaps, and cosmetics and to increase the foaming of beer and soft drinks.
Plant Families that contain significant saponins are: Amaryllidaceae, Convolvulaceae, Dioscoreaceae, Lamiaceae, Lecythidaceae, Liliaceae, Loganiaceae, Meliaeae, Menispermacea, Papilionaceae, Solanaceae, Sapindaceae, Sapotaceae, Scrophulariaceae, Solanaceae, Verbenaceae.