Review of saponin diversity in sea cucumbers belonging to the family Holothuriidae

Saponins are secondary metabolites produced by holothurians. Structurally, they are triterpene glycosides that play an important role in chemical defense and possess a wide spectrum of pharmacological effects. This review highlights the very high diversity of saponins detected in different species of the family Holothuriidae. No less than 59 triterpene glycosides are reported. Several saponins are shared by many species but others are very specific. Overall, most species appear to possess a specific congener mixture. The most evident inter-specific differences that can be highlighted among Holothuriidae are based on the presence or absence of a sulfate group attached to the carbohydrate chain of their saponins. Within a single animal, saponin mixtures also present different concentrations and compositions depending on the organ, with Cuvierian tubules showing the highest saponin concentrations. All of the data combined indicate a complex chemical defence mechanism with different sets of saponins originating from different body compartments and presenting different properties in relation to their ecological role(s).