Selective <i>in vitro</i> antitumor and lymphoproliferative activities of <i>Dioscorea bulbifera</i> extract

Purpose: To assess the anticancer properties of Dioscorea bulbifera extract in vitro. Methods: Murine L5178Y-R lymphoma, MCF-7 and MDA-MB-231 human breast cancer, as well as human HepG2 hepatocarcinoma cells, were treated with varying concentrations of ethanol, methanol and aqueous extracts of D. bulbifera tubers for 48 h to evaluate their in vitro cytotoxic activities. Viability was determined using MTT assay, while the selective cytotoxicity of D. bulbifera extracts against tumor cells was assessed in normal murine splenocytes and thymocytes. Furthermore, 1H-NMR spectra of D. bulbifera extracts were analyzed by nuclear magnetic resonance (NMR) spectroscopy. Results: Significant (p < 0.05) cytotoxic activities (ranging from 58 to 72 %) were obtained for ethanol and methanol extracts against L5178Y-R, MCF-7 and MDA-MB-231 tumor cell lines when compared to untreated controls. Ethanol and methanol extracts did not affect the viability of normal murine thymocytes and splenocytes. In addition, the aqueous extract stimulated the proliferation of resting and concanavalin A-activated thymic and splenic cells. The presence of steroidal saponins and clerodane diterpenes in methanol and ethanol extracts, as well as carbohydrates in the aqueous extract, was demonstrated by NMR analysis. Conclusion: Ethanol and methanol extracts of D. bulbifera show selective cytotoxic activity against murine and human tumor cells, without affecting normal cells, whereas the aqueous extract stimulated the proliferation of murine thymus and spleen cells.