Extraction, Identification and Biological Activities of Saponins in Sea Cucumber Pearsonothuria graeffei

Secondary metabolism in marine organisms produces a diversity of biologically important natural compounds that are not present in terrestrial species. Sea cucumbers belong to the invertebrate Echinodermata and are famous for their nutraceutical, medical and food values. They are known for possession triterpenoid glycosides (saponins) with various ecological roles. The current work aimed to separate, identify and test various biological activities (antibacterial, antifungal, antileishmanial and anticancer properties) of saponins produced by the holothurian Pearsonothuria graeffei from the Red Sea, Egypt.

The structures were identified by 1D and 2D NMR (1H, 13C, TOCSY, COSY, HSQC, HMBC, and ROESY) experiments and acid hydrolysis. The crude and purified fractions was analyzed using matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS)/MS to identify saponins and characterize their molecular structures. Partially purified fraction, mainly containing compounds 1 and 2, was screened for its antifungal activity against three clinical isolates of Candida albicans (Candida 580 (1), Candida 581(2) and Candida MEO47228. Antileishmanial activity against Leishmania major and toxicity on colon cell-line were also evaluated.

Two lanostane type sulfated triterpene monoglycosides were isolated from the Holothurian Pearsonothuria graeffei from the Red Sea, Egypt. Holothurin A (1) and echinoside A (2) triterpene saponins were separated by reversed phase semi-preparative HPLC. LC50 values (µg/mL); calculated for the fraction containing saponins 1 and 2 as major constituents; against Candida albicans, Leishmania major and colon cell-line were 10, 20 and 0.50, respectively.

Consequently, this study demonstrated the potential use of sea cucumber Pearsonothuria graeffei not only as appreciated functional food or nutraceuticals but also as the source of functional ingredients for pharmaceutical products with antifungal, antileishmanial and anticancer properties.