Two new sulfated triterpene glycosides, philinopsides A (1) and B (2), were isolated from the sea cucumber Pentacta quadrangularis. Their structures were established by extensive spectral analysis (2D-NMR and MS) and chemical evidence. Philinopside A (1) and B (2) showed significant cytotoxicity (ED 50 0.75 -3.50 mg/ml) against ten tumor cell lines. Compound 1 also significantly inhibited the proliferation, migration, and tube formation of human microvascular endothelial cells.
Introduction. -As a part of our ongoing investigation on biologically active triterpene glycosides from sea cucumbers, we decided to focus our attention on the saponins of the South China sea cucumber Pentacta quadrangularis, collected near Guangdong province, China. In this paper, we describe the isolation of philinopside A (1) and philinopside B (2), the main components of the polar extracts, whose structures were determined by 1 H-and 13 C-NMR and 2D (DQCOSY, HMQC, HMBC, and NOESY) NMR spectra, and ESI-MS studies, as well as by comparison with NMR data of related saponins.
Results and Discussion. -The EtOH extracts of P. quadrangularis (5 kg, dry weight) were sequentially submitted to column chromatography (DA-101 resin and silica gel) giving the fraction containing philinopsides A (1) and B (2). Compounds 1 and 2 were further isolated and purified by reversed-phase HPLC (Zobax-SB-C 18 ).
Philinopside A (1) was obtained as a colorless amorphous powder. Its molecular formula was determined as C 55 H 85 NaO 25 S from the pseudomolecular-ion peak at m/z 1223.4896 (M + Na) + in the HR-ESI-MS (positive-ion mode). The 1 H-and 13 C-NMR spectra of 1 (Tables 1 and2) suggested the presence of a triterpene aglycon with two olefinic bonds and one ester and one lactone carbonyl group bonded to an oligosaccharide chain composed of four sugar units. A comparison of the spectral data of 1 with those of published saponins showed that the aglycon part of 1 was identical to that