Molecular Networking-Based Analysis of Cytotoxic Saponins from Sea Cucumber Holothuria atra .

The saponin composition of a specimen of black sea cucumber, Holothuria atra collected in the Persian Gulf was studied by a combined approach including LC-MS/MS, Molecular Networking, pure compound isolation, and NMR spectroscopy. The saponin composition of Holothuria atra turned out to be more complex than previously reported. The most abundant saponins in the extract ( 1 ⁻ 4 ) were isolated and characterized by 1D- and 2D-NMR experiments. Compound 1 was identified as a new triterpene glycoside saponin, holothurin A5. The side chain of the new saponin 1 , unprecedented among triterpene glycosides, is characterized by an electrophilic enone function, which can undergo slow water or methanol addition under neutral conditions. The cytotoxic activity of compounds 1 ⁻ 4 , evaluated on the human cervix carcinoma HeLa cell line, was remarkable, with IC50 values ranging from 1.2 to 2.5 µg/mL.