Molecular Networking-Based Analysis of Cytotoxic Saponins from Sea Cucumber <i>Holothuria atra</i>

• Main Authors: Laura Grauso, Afsaneh Yegdaneh, Mohsen Sharifi, Alfonso Mangoni, Behzad Zolfaghari, Virginia Lanzotti
• Format: Article
• Language: English
• Published: MDPI AG 2019-02-01
• Series: Marine Drugs
• Subjects: sea cucumbers; holothurians; saponins; triterpene glycosides; LC-MS/MS; molecular networking; cytotoxic activity
• Online Access: https://www.mdpi.com/1660-3397/17/2/86

The saponin composition of a specimen of black sea cucumber, <i>Holothuria atra</i> 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 <i>Holothuria atra</i> turned out to be more complex than previously reported. The most abundant saponins in the extract (<b>1</b>&#8315;<b>4</b>) were isolated and characterized by 1D- and 2D-NMR experiments. Compound <b>1</b> was identified as a new triterpene glycoside saponin, holothurin A5. The side chain of the new saponin <b>1</b>, 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 <b>1</b>&#8315;<b>4</b>, evaluated on the human cervix carcinoma HeLa cell line, was remarkable, with IC₅₀ values ranging from 1.2 to 2.5 &#181;g/mL.