AVO inhibits the growth of HL-60 cells in a dose- and time-dependent manner. (A) HL-60 cells were treated with varying concentrations of AVO-l or AVO-b (0.0 to 2.0 μg/mL) for 24 h and the viability was analyzed by MTT assay as described in the methods. (B) HL-60 cells were incubated with 1.0 μg/mL of either AVO-l or AVO-b for different periods of time (0 to 48 h) and cell viability was assessed by the MTT assay. The control represents cells incubated under similar conditions in the absence of essential oil. The percentage of cell viability in each sample was expressed relative to untreated control, which was considered as a 100%. HL-60 cells were also treated with 8.0 μM etoposide under similar conditions as positive controls. The results shown represent the mean ± SD of three independent trials. Statistical analysis showed that all samples are significantly different (p < 0.05), when compared to untreated control without AVO or etoposide.