Structures and Bioactivities of Six New Triterpene Glycosides, Psolusosides E, F, G, H, H1, and I and the Corrected Structure of Psolusoside B from the Sea Cucumber Psolus fabricii.

Olesya S Malyarenko,Alexandra S Silchenko,Sergey A Avilov,Ekaterina A Chingizova,Anatoly I Kalinovsky,Pavel S Dmitrenok,Vladimir I Kalinin,Pelageya V Andrijaschenko,Svetlana P Ermakova,Roman S Popov

doi:10.3390/md17060358

Abstract

Seven sulfated triterpene glycosides, psolusosides B (1), E (2), F (3), G (4), H (5), H1 (6), and I (7), along with earlier known psolusoside A and colochiroside D have been isolated from the sea cucumber Psolus fabricii collected in the Sea of Okhotsk. Herein, the structure of psolusoside B (1), elucidated by us in 1989 as a monosulfated tetraoside, has been revised with application of modern NMR and particularly MS data and proved to be a disulfated tetraoside. The structures of other glycosides were elucidated by 2D NMR spectroscopy and HR-ESI mass-spectrometry. Psolusosides E (2), F (3), and G (4) contain holostane aglycones identical to each other and differ in their sugar compositions and the quantity and position of sulfate groups in linear tetrasaccharide carbohydrate moieties. Psolusosides H (5) and H1 (6) are characterized by an unusual sulfated trisaccharide carbohydrate moiety with the glucose as the second sugar unit. Psolusoside I (7) has an unprecedented branched tetrasaccharide disulfated carbohydrate moiety with the xylose unit in the second position of the chain. The cytotoxic activities of the compounds 2–7 against several mouse cell lines—ascite form of Ehrlich carcinoma, neuroblastoma Neuro 2A, normal epithelial JB-6 cells, and erythrocytes—were quite different, at that hemolytic effects of the tested compounds were higher than their cytotoxicity against other cells, especially against the ascites of Ehrlich carcinoma. Interestingly, psolusoside G (4) was not cytotoxic against normal JB-6 cells but demonstrated high activity against Neuro 2A cells. The cytotoxic activity against human colorectal adenocarcinoma HT-29 cells and the influence on the colony formation and growth of HT-29 cells of compounds 1–3, 5–7 and psolusoside A was checked. The highest inhibitory activities were demonstrated by psolusosides E (2) and F (3).

Highlights

The sea cucumbers triterpene glycosides are long-time investigated natural compounds characterized by significant structural diversity, exhibiting a broad spectrum of biological activity [1,2,3,4,5,6,7,8,9].Some of them are under study as marine drugs.The investigation of a complicated glycoside composition of the sea cucumber Psolus fabricii (Psolidae, Dendrochirotida) was started in the 1980s of XX century
We have recommenced the studies on the glycosides of P. fabricii that resulted in the isolation of eight new hexaosides, psolusosides
The concentrated ethanolic extract of P. fabricii was re-extracted with CHCl3 /MeOH, concentrated, and delipidized with EtOAc/H2 O

Summary

Introduction

The sea cucumbers triterpene glycosides are long-time investigated natural compounds characterized by significant structural diversity, exhibiting a broad spectrum of biological activity [1,2,3,4,5,6,7,8,9]. The investigation of a complicated glycoside composition of the sea cucumber Psolus fabricii (Psolidae, Dendrochirotida) was started in the 1980s of XX century. Mar. Drugs 2019, 17, 358; doi:10.3390/md17060358 www.mdpi.com/journal/marinedrugs. Mar. Drugs 2019, 17, 358 psolusosides A [10,11] and B [12,13], had been isolated in that time. We have recommenced the studies on the glycosides of P. fabricii that resulted in the isolation of eight new hexaosides, psolusosides

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