+)-tephrodin: a novel flavone with antiplasmodial activity from tephrosia purpurea

Abstract

In our continued search for antiplasmodial agents with unique structures from Tephrosia species, the isolation, characterization and antiplasmodial activity of a novel flavone and three known flavonoids are hereby report ed from the dichloromethane/Methanol (1:1) extract of the stem of Tephrosia purpurea . The crude extract showed good antiplasmodial activity against the chloroquine - sensitive (D6) and chloroquine - resistant (W2) strains of Plasmodium falciparum (IC 50 = 4.1 ± 0.4 and 1.9 ± 0.2  g/mL, respectively). Chromatographic separation of the crude extract afforded the novel flavone having a unique substituent with seven carbon atoms at C - 7/C - 8 ring junction [trivial name (+) - tephrodin], along with the known flavonoids t achrosin, obovatin methyl ether and derrone. The relative configuration and the most stable conformation in (+) - tephrodin was determined by NMR and theoretical energy calculations. The new flavone was tested for in vitro antiplasmodial activity with IC 50 = 14.0 ± 1.5  M against D6 and 18.0 ± 2.4  M against W2 strains of P. falcipuram , without significant cytotoxicity (IC 50 > 100 μM) against mammalian African monkey kidney (vero) and human larynx carcinoma (HEp2) cell lines.