Using various chromatographic separations, three triterpene tetraglycosides (1-3), including one new compound, namely stichorrenoside E (1) along with thelenotoside B (2) and deacetyl thelenotoside B (3), were isolated from the MeOH extract of the Vietnamese sea cucumber Stichopus horrens. Their structures were confirmed by spectroscopic experiments, such as 1D and 2D NMR and HR-ESI-MS. Deacetylated thelenotoside B (3) is firstly isolated as a natural product. Among these compounds, thelenotoside B (2) showed strong cytotoxicities against five human cancer cell lines as HepG2, KB, LNCaP, MCF7 and SK-Mel2 with the IC50 values from 0.95 ± 0.08 to 1.90 ± 0.13 μM, whereas stichorrenoside E (1) and deacetyl thelenotoside B (3) exhibited significant activities with the IC50 values from 6.87 ± 0.25 to 11.62 ± 1.05 μM.
Keywords: Stichopodidae; Stichopus horrens; cytotoxicity; triterpene saponin.