*2.8. Cell Viability*

Cell viability was analyzed according to the protocol described by Denizot and Land [36] by dispensing osteoblast MC3T3-E1 cells in a 96-well plate at 2 × 10<sup>3</sup> cells/well and subsequently pre-incubating them in a CO2 incubator for 24 h. After incubation, the MC3T3-E1 cells were treated with different concentrations of plant sample for 72 h. The 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT solution) at 5mg·mL−<sup>1</sup> was added to each well and maintained at 37 ◦C for 4 h. Then, the resultant formazan crystals were dissolved in dimethyl sulfoxide (DMSO). The absorbance of the mixture was taken using a microplate reader (Thermo Fisher Scientific Instrument Co., Ltd., Shanghai, China) at 570 nm.
