In vitro anti-tumor activity of isorhamnetin isolated from Hippophae rhamnoides L. against BEL-7402 cells

Isorhamnetin, a flavonol aglycone, isolated from the traditional Chinese medicine Hippophae rhamnoides L., was investigated in its cytotoxicity and its influence on human hepatocellular carcinoma cells (BEL-7402). The cytotoxic effects of isorhamnetin showed dose- and time-dependency against BEL-7402 cells, with IC50 equal to 74.4 ± 1.13 μg ml−1 after treatment with isorhamnetin for 72 h. Cytotoxicity of the flavonols on tumor cells depends on cellular accumulation of the drugs. The amount of isorhamnetin accumulated in BEL-7402 cells was assayed by high-performance liquid chromatography (HPLC) and showed that isorhamnetin could permeate the cell membrane into the cell. Staining with Hoechst 33258 showed fragmentation and condensation of chromatin in the cell treated with 50 μg ml−1 isorhamnetin for 48 h. Flow cytometric analysis was performed to determine hypodiploid cells. The results of flow cytometry assay indicated that the percentage of hypodiploid BEL-7402 cells were 13.77 ± 1.05% after 48 h treatment with 50 μg ml−1 isorhamnetin. The treatment resulted in the appearance of a hypodiploid peak (sub-G0/G1 peak), probably due to the presence of cells in apoptosis and apoptotic bodies with DNA content less than 2n. To our knowledge, this is the first report against human hepatocellular carcinoma cells (BEL-7402) of isorhamnetin.