RESUMEN
The efficiency of cancer chemotherapy is seriously hampered by the development of resistance of neoplastic cells to cytotoxic agents. In the present investigation, the cytotoxicity of the dichloromethane-methanol (1:1) extract of Acacia sieberiana (ASL), fractions (ASLa-c) from the leaves and isolated compounds: chrysoeriol-7-O-rutinoside (1), luteolin-7-O-rutinoside (2), chrysoeriol-7-O-ß-D-glucopyranoside (3), Apigenin-7-O-ß-D-glucopyranoside (4), luteolin-3',4'-dimethoxylether-7-O-ß-D-glucoside (5) and luteolin (6) was investigated. The study was extended to the assessment of the mode of induction of apoptosis by ASL. The resazurin reduction assay (RRA) was used for cytotoxicity studies. Assessments of cell cycle distribution, apoptosis, and reactive oxygen species (ROS) were performed by flow cytometry. A caspase-Glo assay was used to evaluate caspase activities. Botanicals ASL, ASLb and ASLc as well as doxorubicin displayed observable IC50 values towards the nine tested cancer cell lines while ASLa and compounds 1-7 had selective activities. The IC50 values ranged from 13.45 µg/mL (in CCRF-CEM leukemia cells) to 33.20 µg/mL (against MDA-MB-231-BCRP breast adenocarcinoma cells) for ASL, from 16.42 µg/mL (in CCRF-CEM cells) to 29.64 µg/mL (against MDA-MB-231-pcDNA cells) for ASLc, and from 22.94 µg/mL (in MDA-MB-231-BCRP cells) to 40.19 µg/mL (against HCT116 (p53-/-) colon adenocarcinoma cells) for ASLb (Table 1), and from 0.02 µM (against CCRF-CEM cells) to 122.96 µM (against CEM/ADR5000 cells) for doxorubicin. ASL induced apoptosis in CCRF-CEM cells, mediated by ROS production. Acacia sieberiana is a good cytotoxic plant and should be further explored to develop an anticancer phytomedicine to combat both sensitive and drug resistant phenotypes.