Cellular up take of RRR-α- and RRR-γ-tocopherol is time and concentration dependent, with RRR-γ-tocopherol accumulating to a higher intracellular concentration. A) SW480 cells were treated with varying concentrations of RRR-α- and RRR-γ-tocopherol for 24 hours. B) SW480 cells were treated with 100 μM RRR-α- or RRR-γ-tocopherol, collected, counted and subjected to HPLC analysis after 24, 48 and 72 hour treatments. Values are average of three independent experiments and error bars represent standard deviation. Time-dependent HPLC values were normalized to cell counts due to cell death at longer time intervals.