Three new monosulfated triterpene glycosides, calcigerosides B (2), C(1) (3), and C(2) (4), along with the known cucumarioside G(2) (1), have been isolated from the sea cucumber Pentamera calcigera. Their structures have been deduced from extensive spectral analysis (NMR and MS) and chemical evidence. Compounds 2-4 present a novel pentasacharide chain never reported before in sea cucumber triterpene glycosides. The desulfated derivatives of calcigerosides B, C(1), and C(2) (5, 7, and 9, respectively) showed moderate cytotoxicity (IC(50) = 5 microg/mL) against a selection of four human and mouse tumor cell lines.
Frondoside C (1) is a new sulfated nonholostane triterpene glycoside obtained (with the glycosides closed by aglycone structure as impurities) from the sea cucumber Cucumaria frondosa. Its structure has been elucidated on the basis of spectral data (NMR and MS) of compound 1 and of its desulfated derivative (2) obtained by solvolysis. Frondoside C (1) is just the seventh glycoside reported from sea cucumbers, having a lanostane-type aglycone devoid of the typical 18(20)lactone ring.Résumé : On a isolé un nouveau glycoside sulfaté du triterpène nonholostane, le frondoside C (1) (comportant des glycosides de la structure aglycone comme impuretés), à partir du concombre de mer Cucumaria frondosa. On a déterminé sa structure en se basant sur des données spectrales (RMN et SM) du composé 1 et de son dérivé désulfaté (2) obtenu par solvolyse. Le frondoside C (1) n'est que le septième glycoside à avoir été observé dans les concombres de mer, avec un aglycone de type lanostane ne comportant pas de cycle lactone typique en 18(20).Mots clés : Cucumaria frondosa, concombres de mer, frondosides, glycosides de triterpène, activité antitumorale. [Traduit par la rédaction]The sea cucumber Cucumaria frondosa Gunnerus (Cucumariidae) is a widespread benthic animal inhabiting the North Atlantic and western Arctic seas. Previous studies of this sea cucumber have yielded two new holostane pentaglycosides, the monosulfated frondoside A (1) and the disulfated frondoside B (2). More recently, we have isolated a new minor monosulfated tetraoside frondoside A 1 , along with frondoside A, from specimens of C. frondosa collected in Barents Sea (3).Continuing with our investigations on bioactive secondary metabolites of marine origin, we report here our results on the study of the more polar triterpene glycosides from C. frondosa, with the isolation of a new saponin that we named frondoside C. Column chromatography on polychrom-1 (powdered Teflon) of the ethanolic extract of C. frondosa gave a mixture of glycosides that was separated by column chromatography on silica gel, affording frondoside C (1) accompanied by very small amounts of other polar glycosides with identical carbohydrate chain. Attempts to purify 1 by HPLC were unsuccessful. To establish wholly its structure, we resorted to spectroscopic analysis of impure 1 and the pure compound 2 that resulted from solvolysis of 1. Thus, solvolysis of 1 with pyridine-dioxane mixture afforded, after HPLC purification, the pure desulfated derivative 2.
New cytotoxic triterpene oligoglycoside disulfates, cucumariosides A3 (1) and A6-2 (2), have been isolated from the sea cucumber Cucumaria japonica. The trisulfated cucumarioside A?-3 (4) was found to be the major component in the glycoside fraction of Cucumaria miniata. The structures were assigned on the basis of extensive spectral data (NMR and MS), selective solvolysis of desulfated derivative 3 and other chemical evidence. The presence or absence of a carbonyl group at C-16 of the aglycone and of sulfate groups at C-6 of the glucose and 3-0-methylglucose units are interpreted in terms of the functional evolution of sea cucumbers in order to improve their defensive system. Both (1) and (2) are cytotoxic in vitro at ICs0 = 1 pg/ml against a selection of five human and mice tumoral cell lines.As a continuation of our studies on the structure and biological role of triterpene oligoglycosides from holothurians belonging to the genus Cucumaria [11[21[31[41, we have turned our attention to the glycoside content of two members of that genus, namely Cucumaria juponica and Cucumaria miniata, collected by a trawl in the Northern Pacific Ocean. In this paper we report the isolation from C. japonica of two new highly cytotoxic glycosides named as cucumariosides A3 (1) and A6-2 (2), and also of cucumarioside A7-3 (4), a major product in C. miniata, which has previously been reported as a minor component of C. juponica.The ethanolic extracts of Cucumaria japonicu (100 kg wet) were sequentially submitted to column chromatogrdphy on Polychrom-1 (powdered Teflon) and silica gel to afford a glycoside fraction. Separation and isolation of the individual components of that fraction by reverse phase HPLC on a Silasorb C-18 column gave cucumarioside A3(1) as a solid {m.p. The presence of xylose, quinovose, 3-0-methylglucose and glucose in a 2:l:l:l ratio in the structures of 1 and 2 was deduced by acidic hydrolysis with aqueous 2 N HCI followed by GC-MS analysis of the corresponding aldononitrile peracetates. The existence of sulfate groups in 1 and 2 was demonstrated by solvolysis with dioxanelpyridine that produced the same desulfated derivative (3) from both glycosides. This compound was shown to be identical with that obtained by solvolysis of cucumariosides A2-2['l and A7-lL4I. The presence of sodium and potassium in the sulfate groups was confirmed by atomic absorption spectroscopy data. Therefore, glycosides 1 and 2 should have the same sugar composition, the same architecture of the carbohydrate chain and the same aglycone structure as cucumariosides A2-2 and A7-1, but differ in the number and position of the sulfate groups.
Three new triterpene glycosides, calcigerosides D(1) (1), D(2) (2), and E (3), have been isolated from the sea cucumber Pentamera calcigera. Their structures have been deduced from extensive spectral analysis (NMR and MS) and chemical evidence. All the compounds are disulfated pentaosides differing in aglycon structure and position of sulfate group, which were determined by the measurement of NT(1) values in the cases of glycosides 1 and 2. Glycoside 1 is a nonholostane derivative, that is, it lacks an 18(20)-lactone, which is very rare among the sea cucumber glycosides.
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