In Vitro Anticancer and Cancer-Preventive Activity of New Triterpene Glycosides from the Far Eastern Starfish Solaster pacificus .

Sea stars or starfish (class Asteroidea) and holothurians or sea cucumbers (class Holothuroidea), belonging to the phylum Echinodermata (echinoderms), are characterized by different sets of glycosidic metabolites: the steroid type in starfish and the triterpene type in holothurians. However, herein we report the isolation of eight new triterpene glycosides, pacificusosides D-K ( 1 - 3, 5 - 9 ) along with the known cucumarioside D ( 4 ), from the alcoholic extract of the Far Eastern starfish Solaster pacificus . The isolated new compounds are closely related to the metabolites of sea cucumbers, and their structures of 1 - 3 and 5 - 9 were determined by extensive NMR and ESIMS techniques. Compounds 2 , 5 , and 8 have a new type of tetrasaccharide chain with a terminal non-methylated monosaccharide unit. Compounds 3 , 6 , and 9 contain another new type of tetrasaccharide chain, having 6- O -SO 3 -Glc as one of the sugar units. The cytotoxic activity of 1 - 9 against non-cancerous mouse epidermal cells JB6 Cl41 and human melanoma cell lines SK-MEL-2, SK-MEL-28, and RPMI-7951 was determined by MTS assay. Compounds 1 , 3 , 4 , 6 , and 9 showed potent cytotoxicity against these cell lines, but the cancer selectivity (SI > 9) was observed only against the SK-MEL-2 cell line. Compounds 1 , 3 , 4 , 6 , and 9 at the non-toxic concentration of 0.1 μM significantly inhibited neoplastic cell transformation of JB6 Cl41 cells induced by chemical carcinogens (EGF, TPA) or ionizing radiation (X-rays and UVB). Moreover, compounds 1 and 4 at the non-toxic concentration of 0.1 µM possessed the highest inhibiting activity on colony formation among the investigated compounds and decreased the colonies number of SK-MEL-2 cells by 64% and 70%, respectively. Thus, triterpene glycosides 1 and 4 can be considered as prospective cancer-preventive and anticancer-compound leaders.