Growth curve inhibition as assessed by MTT assay in human breast cancer cells (MDA-MB-231 (blue line) and MCF-7 (grey line)). The breast cancer cells were exposed to different doses of HHQ for 48 h at 37 °C. The cell viability in breast cancer cells decreased in dose-dependent fashion. The IC-50 value for MDA-MB-231 and MCF-7 were observed to be 25 μM and 50 μM, respectively. Data are representative of three independent experiments done in triplicates and expressed as mean ± S.E.M. *p < 0.005 represents statistical significant difference between control and HHQ test groups.