Triterpene Glycosides from Antarctic Sea Cucumbers Structures of LIOUVILLOSIDES A4 and A5, two minor disulfated tetraosides having 3-O-Methylquinovose as terminal monosacharide unit from the sea cucumber Staurocucumis liouvillei (Vaney, 1914) Ekman, 1927 Alexandr S. Antonov1, Sergey A. Avilov1, Anatoly I. Kalinovsky1, Pavel S. Dmitrenok1, Vladimir I. Kalinin1, Sergi Taboada2, Manuel Ballesteros2, Conxita Avila2 and Valentin A. Stonik1 1Pacific
Institute of Bioorganic Chemistry of the East Division of the Russian Academy of Sciences, Pr. 100-letya Vladivostoka 159, 690022, Vladivostok, Russian Federation 2Department of Animal Biology (Invertebrates), Faculty of Biology, University of Barcelona, Av. Diagonal 645, 08028 Barcelona, Spain
[email protected];
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INTRODUCTION: Holothurians present a great diversity of triterpene glycosides, belonging mainly to the so called holostane series. Their carbohydrate chains are comprised of two to six monosaccharide units (Kobayashi et al., 1991; Stonik et al., 1999; Kalinin et al., 2005; Chludil et al., 2003). These saponins have been found in many sea cucumber species collected from tropical zones of the Pacific and Indian Oceans (e.g. Stonik et al., 1999), Mediterranean Sea (e.g. Silchenko et al., 2005), North Atlantic (e.g. Silchenko et al., 2007) and North Pacific (Silchenko et al., 2008). However, only three works have focused so far on the study of triterpene glycosides from Antarctic sea cucumbers (Maier et al., 2001; Antonov et al., 2008, 2009). Sea Cucumber Species
New Described Compounds
Triterpene Glycosides from Antarctic Sea Cucumbers I (Antonov et al. 2008)
Background
Triterpene Glycosides from Antarctic Sea Cucumbers II (Antonov et al. 2009)
Staurocucumis liouvillei
LIOUVILLOSIDES A1, A2, A3, B1 & B2
Achlionice violaecuspidata (=Rhipidothuria racowitzai)
ACHLIONICEOSIDES A1, A2 & A3
As a continuation of our studies of triterpene glycosides from Antarctic sea cucumbers we report here the isolation and structural elucidation of two new minor glycosides from S. liouvillei (Liouvilloside A4 & A5):
Liouvilloside A4
Staurocucumis liouvillei
Liouvilloside A5
Sugars
Previous Liouvillosides described from the authors (Antonov et al. 2008)
Liouvilloside A1 Liouvilloside A2 Liouvilloside A3 Liouvilloside B1 Liouvilloside B2
DISCUSSION: The presence of 3-O-methyl-D-quinovose as terminal monosaccharide residue is extremely rare in sea cucumber triterpene glycosides, and it was found only for the previously described liouvillosides A2 and A3 (Antonov et al., 2008). Apart from being a constituent of sea cucumber saponins, 3-O-methyl-D-quinovose was also found in asterosaponins from the starfish Goniopecten demonstrans (De Marino et al., 2000) and Culcita novaeguinea (Tang et al., 2009). MATERIAL & METHODS Animal Material: 23 specimens of Staurocucumis liouvillei (Family Cucumariidae; Order Dendrochirotida) collected near the Sub-Antarctic Island of Bouvet (54° 22,49' S; 003° 17,58' E) by Agassiz trawl on board the research vessel Polarstern [Alfred Wegener Institute for Polar and Marine Research (Bremenhaven, Germany)] during the Antarctic expedition ANT XXI/2 (2003) at a depth of 134 m.
Frozen specimens of S. liouvillei
Extraction & Isolation: frozen sea cucumbers were minced and extracted twice with refluxing 70% EtOH. The dry wt of the residue was 5.6 g. The combined extracts were concentrated dryness in vacuo, dissolved in water and chromatographed on a Polychrom-1 column, eluting first inorganic salts and polar impurities with water and then the glycosides with 60% acetone. The latter fraction was submitted to chromatography on Si gel columns eluting with CHCl3/EtOH/H2O (100:100:17 and 100:125:25) solvent systems to give 47 and 95 mg of glycoside fractions A and B containing di- and trisulfated glycosides respectively, as individual spots on TLC. Fraction A was subsequently separated by HPLC on a Supelvo Sil column with CHCl3/EtOH/NH4OAc (1 N water solution) (65:45:2) as mobile phase, Supelco C-18 column with EtOH/H2O/NH4OAc (1 N water solution) (55:45:2) as mobile phase, and an Agilent ChiraDex column with CH3CN/H2O/NH4OAc (1 N water solution) as mobile phase to give of 1.2 mg of liouvilloside A1, 1.3 mg of liouvilloside A2, 2.8 mg of liouvilloside A39, 0.6 mg of liouvilloside A4 (1) and 0.4 mg of liouvilloside A5 (2).
Experimental procedures: NMR spectra were recorded on an ADVANCE III-700 Bruker spectrometer at 700.13 MHz/126.04 MHz (1H/13C) in C5D5N at 35oC with TMS as an internal reference ( = 0). The ESIS MS (negative ion mode) were recorded using an Agilent 6510 Q-TOF apparatus; sample concentration 0.01 mg/ml, CH3OH/H2O (1:1) as a solvent. The MALDI TOF MS (positive ion mode) were recorded using a Bruker apparatus, model BIFLEX III, with impuls extraction of ions, on an -cyano-4-hydroxycinnamic acid matrix. HPLC was performed using a Agilent 1100 chromatograph equipped with a differential refractometer on Supelco Sil (4.6 250 mm, 5 m), C-18 (10 250 mm, 5 m), and cyclodextrin Agilent ChiraDex (4 244 nm, 5 m) columns. REFERENCES: Antonov et al., 2008. Journal of Natural Products 71: 1677-1685; Antonov et al., 2009. Journal of Natural Products 72:33-38; Chludil et al., 2003. In: Studies in Natural Products Chemistry, Elseviewer Science: 587616; De Marino et al., 2000. Journal of Organic Chemistry 21: 4093-4098; Kalinin et al., 2005. Phytochemistry Reviews 4: 221-236; Kobayashi et al., 1991. Chemical and Pharmaceutical Bulletin 39: 2282-2287; Maier et al., 2001. Journal of Natural Products 64: 732-736; Silchenko et al., 2005. Journal of Natural Products 68: 564-567; Silchenko et al., 2007. Canadian Journal of Chemistry 85: 626-636; Silchenko et al., 2008. Journal of Natural Products 71: 351-356; Stonik et al., 1999. Journal of Natural Toxins 8: 235-248; Tang et al., Journal of Natural Products 72: 284-289. ACKNOWLEDGEMENTS: The authors acknowledge the financial support of a Grant of Presidium of the Russian Academy of Science “Molecular and cell biology” and the President of the Russian Federation Program for Support of the Leading Scientific Schools Grant No. 3531.2010.4. Thanks are also due toW. Arntz and the crew of R/V Polarstern (AWI) for their help during the cruise ANTXXI/2. A. Bosch is also acknowledged for her help in the identification of the holothurians. We are thankful for the support of the ECOQUIM and ACTIQUIM projects (REN2002-12006-E/ANT, REN2003-00545, and CGL2004-03356/ANT) from Spain.
13th International Symposium on Marine Natural Products. October 2010 (Phuket, Thailand)
