Mitochondrial dysfunction is another key event of apoptosis. An
important parameter of mitochondrial dysfunction is the loss of
mitochondrial membrane potential (DWm) (Kroemer, 2003). Loss
of DWm is lethal to cells because they become bioenergetically
deficient (Crompton, 2000). Breakdown of DWm in turn leads to
the release of cytochrome c into the cytosol and activation of
caspase cascades that result in cell death. The design of mitochondria-
targeted therapeutic strategies for cancer has recently been
reviewed (Fulda et al., 2010). The present study demonstrated that
the three xanthones induced loss of DWm. These findings are consistent
with previous studies. Matsumoto et al. (2004) reported
that a-mangostin preferentially targeted mitochondria with loss
of DWm, decrease in ATP, ROS accumulation and cytochrome c/
AIF release in human leukaemia HL60 cells. Nakagawa et al.
(2007) showed that a-mangostin induced decreased DWm with
release of endonuclease-G from mitochondria. Further experiments
are required to understand the precise molecular mechanism
of mitochondrial pathway induced by the three xanthones
studied.