Phenanthrenes with Potent Antitrypanosomal Activity from Roots of Cymbidium Great Flower 'Marylaurencin'

In the course of the searching for new antitrypanosomal drug leads, twelve phenanthrenes (1-11 and 13) from roots of Cymbidium Great Flower 'Marylaurencin' showed remarkable in vitro antitrypanosomal activity. Their structures were identified by the analysis of high resolution-electron ionization (HR-EI)-MS, 1H and 13C NMR spectra including extensive two-dimensional (2D) NMR experiments and the comparison with the literature data. The IC50 values of 1-5, 7 and 8 for in vitro antitrypanosomal activity against Trypanosoma brucei brucei GUTat 3.1 strain were 0.16, 0.064, 0.23, 0.11, 0.32, 1.25 and 0.057 μg/mL, respectively. In particular, 8 show potent activity around 28 times that of suramin, which is used for the remedy of African trypanosomiasis.