Cytotoxicity Screening of Compounds

Compounds (1–18) were tested for cytotoxicity against the MDA-MB-435^{27 (link)} human melanoma (HTB-129, ATCC) and the HT-29 human colon cancer (HTB-38,ATCC) cell lines as described previously.^{26 (link),28 (link)} Briefly, the cell lines were propagated at 37 °C in 5% CO₂ in RPMI 1640 medium, which was supplemented with 10% fetal bovine serum, 100 units/mL penicillin, and 100 μg/mL streptomycin. The cells were harvested by trypsinization while in their log phase and washed twice to remove all traces of enzyme. In every well of a 96-well plate (Microtest 96, Falcon), about 5,000 cells were seeded and incubated overnight in 5% CO₂ at 37 °C. Tested compounds dissolved in DMSO were incubated with the cells for 72 h at 37 °C and evaluated for viability with a commercial absorbance assay (CellTiter 96 AQ_ueous One Solution Cell Proliferation Assay, Promega Corp, Madison, WI). IC₅₀ values are expressed in μM relative to the solvent (DMSO) control. Vinblastine was used as a positive control.