H2AX and central nervous system cancer: Pure parvifloron D, 7α-acetoxy-6β-hydroxyroyleanone and 6,7-dehydroroyleanone isolated from P. madagascariensis and P. ecklonii may exhibit anticancer effects in H7PX glioma cell line by inducing apoptosis, G2/M cell cycle arrest and DSBs (double strand breaks), indicated by elevated phosphorylated H2AX, decreasing mitochondrial membrane potential, and by changing the level of expression of pro and anti-apoptotic genes.