Inter- and intra-organ spatial distributions of sea star saponins by MALDI imaging
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Saponins are secondary metabolites that are abundant and diversified in echinoderms. Mass spectrometry is increasingly used not only to identify saponin congeners within animal extracts but also to decipher the structure/biological activity relationships of these molecules by determining their inter-organ and inter-individual variability. The usual method requires extensive purification procedures to prepare saponin extracts compatible with mass spectrometry analysis. Here, we selected the sea star Asterias rubens as a model animal to prove that direct analysis of saponins can be performed on tissue sections. We also demonstrated that carboxymethyl cellulose can be used as an embedding medium to facilitate the cryosectioning procedure. Matrix-assisted laser desorption/ionization (MALDI) imaging was also revealed to afford interesting data on the distribution of saponin molecules within the tissues. We indeed highlight that saponins are located not only inside the body wall of the animals but also within the mucus layer that probably protects the animal against external aggressions.
KeywordsSaponin Sea stars Mass spectrometry MALDI-mass spectrometry imaging
The MS laboratory acknowledges the “Fonds de la Recherche Scientifique (FRS-FNRS)” for its contribution to the acquisition of the Waters Q-ToF Premier Mass Spectrometer. E.H. and P.F. are, respectively, Postdoctoral Researcher and Research Director of the FRS-FNRS. M.D. is grateful to the F.R.I.A. for financial support. This work was supported by the FRFC research project no. T.0056.13 and in part by the EU FP7-OCEAN Project “Low-toxic cost-efficient environment-friendly antifouling materials” (BYEFOULING) under Grant Agreement no. 612717.
Conflict of interest
The authors declare that they have no competing interests.
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