Analysis of Plant Saponins

Saponins are naturally occurring secondary metabolites, which can be widely found in a number of plant families. They can be found in different parts of plants usually as multicomponent mixtures. They are composed of the triterpene or steroidal aglycone to which a number of sugars in the form of one, two, or three sugar chains are attached. Depending on the chemical structure, they show different biological activities. The common feature of these compounds is surface activity, so they can be used as emulsifiers, and in the past, they were used as soap substitutes. Some of them have found application in food industry, whereas the others are being considered as antinutritional substances. Owing to the fact that saponins occur in quite complex mixtures, their separation to individual compounds is still a challenge. Also, their determination with chromatographic techniques creates some problems as they are lacking chromophores allowing ultraviolet (UV) detection. Precolumn derivatization, light scattering detection, and liquid chromatography coupled with mass detector are the methods of choice for their determination. Keywords: saponins; glycosides; steroids; triterpenes; analytical methods