Triterpene glycosides from Antarctic sea cucumbers IV. Turquetoside A, a 3-O-methylquinovose containing disulfated tetraoside from the sea cucumber Staurocucumis turqueti (Vaney, 1906) (=Cucumaria spatha)

A novel triterpene holostane disulfated tetrasaccharide olygoglycoside, turquetoside A, having a rare terminal 3-O-methyl-D-quinovose, was isolated from the Antarctic sea cucumber Staurocucumis turqueti. Its structure was elucidated using 2D NMR procedures (HMBC, HSQC, ROESY) and mass-spectrometry. The occurrence of 3-O-methyl-D-quinovose in triterpene glycosides in S. turqueti and in the congeneric Antarctic sea cucumber Staurocucumis liouvillei suggests that the presence of this sugar in carbohydrate chains of triterpene glycosides is a taxonomical character of the genus Staurocucumis.