Extraction et évaluation de l’activité biologique des saponines ( glycosides de stéroïde) de l’étoile de mer Echinaster (Echinaster) sepositus (Retzius, 1783).

Abstract

Our work focuses on the study of saponins isolated from the starfish Echinaster sepositus. Saponins are extracted from bodywall (aboral face and oral face), gonads, stomach and pyloric caeca by different techniques of chemistry. From the in vitro hemolytic tests, we have noted an important hemolytic activity which depends on the concentration of saponins, the duration and temperature of incubation with the blood red cells. The hemolytic performance of the five saponins extracts is different. The gonads’s and bodywall saponins are the most active in blood red cells. Mechanisms that could explain this difference are discussed. A comparative study of hemolytic power obtained from gonads of different individuals of Ehinaster sepositus, harvested over a period of one year, demonstrated that saponins are present in the gonads throughout the year and their toxic effect depend on the harvest season. Gonads’s saponins of individuals sampled during autumn show an important hemolytic power. This hemolytic power increases for the extract of winter and decreases for summer’s extracts. This toxic effect showed a clear pattern of fluctuation reflecting seasonal variations of the saponins rate in the gonads. Concentrations are low in summer increase in autumn and are high in winter until the spawning. Throughout our study we evaluated the antimicrobial activity of saponins of the various organs of Echinaster sepositus on Staphylococcus aureus, Escherichia coli and Pseudomonas aeruginosa. The results obtained revealed that only gonads’s saponins of Echinaster sepositus exercise moderate antimicrobial activity against S. aureus, with an inhibition diameter of 1.54 cm and survival rate of about 51%.