SI derivatives inhibit SH-SY5Y and CHP100 cell growth. Both SH-SY5Y and CHP100 cells were exposed to increasing concentration of SI 34 compounds for the indicated periods of time. Proliferation rate was assessed by MTT assay (A) and cell counting (B). Results of MTT test are expressed as percentages of the values detected in untreated cells. Each value is the mean ± S.E.M. of at least three experiments performed in eightplicate (MTT test) or in triplicate (cell counting). *, ** and ***P < 0.05, P < 0.01 and P < 0.001 vs control and SI 34 1 μM; °P < 0.05 vs SI 34 2.5 μM.