Three new phenanthrenes from Monomeria barbata Lindl.

Three new monophenanthrene compounds were isolated from an acetone extract of the tubers of Monomeria barbata Lindl. (Orchidaceae). Using spectroscopic methods, the structures of compounds 1–3 were determined as 1,4,7-trihydroxy-2-methoxy-9,10-dihydrophenanthrene (1), 1-(p-hydroxybenzoyl)-2-methoxy-4,7-dihydroxy-9,10-dihydrophenanthrene (2), 1,3,8-tri(p-hydroxybenzyl)-4-methoxy-phenanthrene-4,7-diol (3). These compounds showed cytotoxicities on four tumor cell lines (HepG2, HL-60, Skov-3, A431).