Cell experiment:

Cytotoxic activities are evaluated using the Sulforhodamine-B (SRB) assay. Exponentially growing cells are seeded into 96-well plates at cell densities to prevent confluence for 96 h. After 24 h, the cells are treated using a dilution series of the compounds for 72 h under normoxic or hypoxic conditions. After treatment, the adherent cells are fixed using 10% TCA at 4°C for 1 h; the cells are washed with ice-cold water and are dyed using 100 μL of 4.4% SRB solution for 10 min. After staining, the plates are washed with 1% acetic acid and air-dried overnight. Three hundred microliters of 20 mM Tris base solution is added, and the absorbance is measured at 540 nm using a 96-well plate reader. The IC50 values indicate the concentrations of the compound that cause 50% cell inhibition. The data are obtained in three independent experiments.

参考文献:

[1]. Willmann M, et al. Characterization of NVX-207, a novel betulinic acid-derived anti-cancer compound. Eur J Clin Invest. 2009 May;39(5):384-94.
[2]. Bache M, et al. Betulinic acid derivatives NVX-207 and B10 for treatment of glioblastoma--an in vitro study of cytotoxicity and radiosensitization. Int J Mol Sci. 2014 Oct 30;15(11):19777-90.