Saponin contents in the starfish Echinaster sepositus: Chemical characterization, qualitative and quantitative distribution

In this study, we report the inter-organ, the sexual and the seasonal variability, of saponins contained in the common Mediterranean starfish Echinaster (Echinaster) sepositus. Saponins were extracted from five distinct body components namely the stomach, the pyloric caeca, the gonads, the oral body wall and aboral body wall. Of both sexes (males and females) collected at different seasons, the saponins mixtures were analyzed by Mass spectrometry (HR-ESI-MS and HR-ESI- MS/MS). Semi-quantitative approach was performed to estimate the variability of the saponin amounts. Our results demonstrated that the diversity of saponins in E. sepositus is higher than previously reported. We highlighted 11 different saponins, including 9 new congeners. Presumptive molecular structures are proposed for 6 molecules on the basis of key-fragmentations identified by HR-ESI-MS/MS. The comparison of the saponin contained in the five different body components revealed that minimum 3 saponins are common in all tissues. In addition, qualitative and quantitative variability of saponins compounds were linked to the organ, sex and the collecting season. The relative highest level of saponins was found in the stomach on the period of active feeding (winter). The significant higher levels of saponins were found in the gonads and oral body wall on the spawning period (summer). Generally, a great inter-organ, sexual and seasonal variability was found in both sexes. These results suggest that saponins probably fulfill several biological functions in E. sepositus. •The saponin content of sea star Echinaster sepositus was described on the base of ESI-HR-MS and ESI-HR-MS/MS analyses.•11 different saponins were highlighted in different organs, including 9 new congeners.•Qualitative and quantitative variability of saponins compounds was revealed in E. sepositus.•The saponins contents show significant inter-organs, sex and season variabilities.