Neobaicalein, a flavonoid from the Scutellaria litwinowii Bornm. Sint. ex Bornm. induced apoptosis in human leukemic cell lines

Objective(s): Neobaicalein is one of the rich plant flavonoids isolated from the roots of Scutellaria spp. In this study, we evaluated and compared cytotoxic activity and the related apoptosis mechanisms of neobaicalein from Scutellaria litwinowii Bornm. Sint. ex Bornm on apoptosis-proficient HL-60 cells and apoptosis-resistant K562 cells.  Materials and Methods: Cell viability, cell apoptosis, caspase activity, and apoptosis-related protein expression were measured using MTS assay, propidium iodide (PI) staining and flow cytometry, caspase activity assay, and western blot analysis, respectively.  Results: Neobaicalein significantly reduced cell viability in a dose-dependent manner using the MTS assay (P 0.05). The IC50 values (µM) against HL-60 and K562 cells after 48 hr treatment were 40.5 and 84.8, respectively. Incubation of HL-60 and K562 cells with 25, 50, and 100 µM neobaicalein for 48 hr, significantly increased the number of apoptotic cells and showed cytotoxic effects compared with the control group. Treatment with neobaicalein significantly increased Fas (P 0.05) and the cleaved form of PARP (P 0.05), and decreased the Bcl-2 levels (P 0.05) in HL-60 cells, whereas neobaicalein significantly increased Bax (P 0.05) and the cleaved form of PARP (P 0.05), and the caspases of the extrinsic and intrinsic pathways including caspases-8 (P 0.0001), -9 (P 0.01), and effector caspase-3 (P 0.0001) levels in K562 cells compared with the control group. Conclusion: It seems neobaicalein might cause cytotoxicity and cell apoptosis through interaction with the different apoptosis-related proteins of apoptotic pathways in HL-60 and K562 cells. Neobaicalein may exert a beneficial protective effect in slowing the progression of hematological malignancies.