Effects of different concentrations and treatment periods of tocotrienols on cell viability of A549 and U87MG cells. (A) Alpha-, (B) gamma- and (C) delta-tocotrienols show significant cytotoxic effects (p < 0.05) against both cancer cells in a concentration- and time-dependent manner. Cell viability is presented as percentage where negative vehicle control cells were regarded as 100% viable. Data are presented as mean ± SD (n = 9). α-T3: alpha-tocotrienol; γ-T3: gamma-tocotrienol; δ-T3: delta-tocotrienol.