Four new phenanthrenes from Monomeria barbata Lindl.

Three biphenanthrene compounds (1-3) and a triphenanthrene compound (4), together with six known biphenanthrene compounds (5-10), were isolated from the tubers of Monomeria barbata Lindl. Their structures were elucidated on the basis of extensive spectroscopic analysis (1D-, 2D-NMR, and HR-ESI-MS). These four new compounds were tested in vitro for the cytotoxic activity against liver carcinoma (HepG-2), promyelocytic leukaemia (HL60), ovarian carcinoma (Skov-3) and epidermoid carcinoma (A431) cancer cell lines and the antioxidant activity in DPPH radical scavenging. Compounds 1-4 exhibited significant cytotoxic activity against HepG-2 and HL60 cell lines, and potent antioxidant activity in DPPH radical scavenging.