Cytotoxic constituents from Viscum coloratum

Abstract

Viscum coloratum (Kom.) Nakai is a perennial, evergreen, semi-parasitic plant which grows on the branches or stems of deciduous trees. It is known as Hujisheng in China (China Pharmacopoeia Committee, 2010). V. coloratum is an important medicinal herb, suitable for commercial production, which has been used for the treatment of various conditions including cancer, cardiovascular diseases, hepatitis, and hemorrhage (Wang et al., 2005). It has been reported that the total alkaloids of V. coloratum exhibited cytotoxic activities against A-549 non-small cell lung, MCF-7 breast, and Eca-109 esophageal cancer cells, respectively (Chen et al., 2005). Phytochemical investigation of V. coloratum also showed the presence of many other types of compounds including fl avonoids, triterpenoids, lignans, and diarylheptanoids (Wang et al., 2005; Leu et al., 2006). Some of them exhibited inhibitory activity on cancer cell growth. For example, homoeriodictyol markedly inhibited the growth of HeLa human uterine carcinoma cells (Akihisa et al., 1988). Oleanolic acid exhibited cytotoxic activity against A-549 non-small cell lung, SK-OV-3 ovary, SK-MEL-2 melanoma, and HCT-15 colon cancer cell lines, respectively (Kim et al., 2000), while syringaresinol inhibited the proliferation of human promyelocytic HL-60 cells (Park et al., 2008). In addition, 1,7-di(3’,4’dihydroxyphenyl)-4-hepten-3-one exhibited cytotoxic activity against UACC-62 melanoma, TK-10 renal, and MCF-7 breast cancer cells, respectively (Martin-Cordero et al., 2001). As part of our program aimed at the isolation of bioactive components, we undertook a detailed chemical study of V. coloratum. In the present paper, the isolation and identifi cation of nineteen compounds, including two new compounds, 1,7-bis(4-hydroxyphenyl)-1,4-heptadien-3-one (8) and 5-hydroxy-3,7,3’-trimethoxyfl avone-4’-O-β-Dglucoside (13), are described. Pachypodol 4 and ombuine 6 were isolated from the family Loranthaceae for the fi rst time. The in vitro antiproliferative activities of compounds 8 and 13 against four human cancer cell lines were also evaluated.