500 mL of a commercial red beet juice containing 362.7 mg of betalains

The cancer cell proliferation inhibitory activity of all natural pigments isolated was evaluated by using the MTT colorimetric assay. The tumor cell lines AGS, HCT-116, MCF-7, NCI-H460, and SF-268 used were maintained in our laboratory at Michigan State University. The cell lines were maintained as adherent cell cultures in RPMI-1640 medium supplemented with 10% FBS, 10 units of penicillin, and 105 mkg/mL streptomycin at 37 C under 5% CO2 in a humidified incubator. The cells were harvested and counted by using a hemacytometer, and the appropriate number of cells (4000-8000 cells/mL) was transferred into 96 well plates and incubated for 24 h prior to the treatment. Betanin and cyanidin-3-O-glucoside were dissolved in water separately and diluted with RPMI-1640 medium to the desired concentrations of 12.5, 25, 50, 100, and 200 mkg/mL. The test compounds were exposed to cells for 48 h. Adriamycin (doxorubicin), dissolved in 0.1% DMSO, was used as the positive control.