The effect of peak 1 on DNA damage and the cell cycle. Flow cytometry analysis of DNA content (top panel) and γH2AX expression (lower panel) in U2OS cells after treatment with fractions of X. aethiopica extract. The cells were treated for 24 h with 20 μg/ml of the various fractions. The percentage of cells with G1 and G2/M DNA content are indicated. The percentage of γH2AX- positive cells above the threshold line indicates the amount of DNA damage.