In vitro Anti-proliferative and Apoptotic Activities of Eurycoma longifolia Jack (Simaroubaceae) on HL-60 Cell Line

Purpose: To investigate the anti-proliferative, apoptotic and differentiating activities of Eurycoma longifolia root extracts on HL-60 leukemic cells. Methods: HL-60 cells were treated with different partially purified sub-fractions (F1 – F3) derived from the resin chromatography of the crude methanol root extract of E. longifolia roots, at different doses and time points. The anti-proliferative activity of E. longifolia was assessed via cell counting and trypan blue exclusion. Apoptosis was evaluated via Annexin-V FITC/IP and Hoechst staining. Flow cytometry and Wright staining were used to assess its differentiation activities. Results: F1 showed unremarkable growth inhibition rate while F2 and F3 showed growth inhibitory effects with median inhibitory concentration (IC50) values of 15.2 and 28.6 ìg/ml, respectively. Treatment with F2 and F3 (100 ìg/ml) for 96 h increased cell death from 3.3 to 95.5 and 76.3 %, respectively. Treatment with F2 (50 ìg/ml) induced apoptosis by 14, 19.5 and 25 % after 24, 48 and 72 h, respectively. No differentiation activity was observed, as indicated by absence of myeloid maturation and a non-significant CD14 positivity (p > 0.05). Conclusion: E. longifolia extract (F2) showed promising anti-leukemic activity and can be a candidate for the development of a drug for the treatment of acute promyelocytic leukemia (APL).