A triterpene glycoside from the black sea cucumber Holothuria atra

Sea cucumber is a soft-bodied, worm-like, echinoderm. It is consumed in its dried form, which is called “bêche-de-mer”. Many reports described the presence of triterpene glycosides (saponins) in sea cucumbers, and especially the Cuvierian tubules are a rich source of this type of compounds [1],[2]. The black sea cucumber, Holothuria atra Jaeger, is one of the commercially important species in Indonesia. However, in contrast to most species of sea cucumber, H. atra does not possess Cuvierian tubules, but saponins were previously isolated from its body wall [3]. In this project, an extensive study of the composition of the body wall of H. atra is carried out, with special interest in its saponin content. Black sea cucumbers were collected in East Java, Indonesia, dried, and extracted with dichloromethane and 80% methanol. Fractionation was carried out by means of liquid partitioning and column chromatography (diaion HP20). Finally, semi-preparative HPLC-DAD-MS allowed for the purification of various saponins, according to their ¹H-NMR spectra. Up till now, the structure of one compound could be fully elucidated, based on 1D and 2D NMR and HRMS data. All NMR data were in correspondence to the data reported by Kitagawa, for desulfated holothurin B [4]. Moreover, the HRMS data of this compound were recorded for the first time and confirmed the identification of the compound as desulfated holothurin B (m/z 803.4250, [M+Na]⁺; calculated for C₄₁H₆₄O₁₄Na: 803.4194; and m/z 485.3267, aglycon). Further research with regard to the structure elucidation of other purified compounds is ongoing.

Fig. 1 Desulfated holothurin B of black sea cucumber Holothuria atra

• References

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• 2 Van Dyck S, Caulier G, Todesco M, Gerbaux P, Fournier I, Wisztorski M. et al. The triterpene glycosides of Holothuria forskali: usefulness and efficiency as a chemical defense mechanism against predatory fish. J Exp Biol. 2011
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• 4 Kitagawa I, Akutsu H, Kyogoku Y, Zubrica H. Structure of Holothurin B A Pharmacologically Active Triterpene-Oligoglycoside From The Sea Cucumber Holothuria leucospilota Brandt. Tetrahedron Lett 1978; 3385: 985-988.