Identification of Two New Phenanthrenes from Dendrobii Herba and Their Cytotoxicity towards Human Hypopharynx Squamous Carcinoma Cell (FaDu).

Two new phenanthrenes, (1,2)-1,7-hydroxy-2,8-methoxy-2,3-dihydrophenanthrene-4(1)-one () and 2,7-dihydroxy-phenanthrene-1,4-dione (), were isolated from the ethyl acetate-soluble fraction of Dendrobii Herba, together with seven known phenanthrenes (-), two bibenzyls (-), and a lignan (). Structures of and were elucidated by analyzing one-dimensional (1D) and two-dimensional (2D)-NMR and High-resolution electrospray ionization mass spectra (HR-ESI-MS) data. The absolute configuration of compound was confirmed by the circular dichroism (CD) spectroscopic method. In cytotoxicity assay using FaDu human hypopharynx squamous carcinoma cell line, compounds -, , , and showed activities, with IC values that ranged from 2.55 to 17.70 μM.