Results: A progressive decrease in complex I, II/III and IV activities was noted with a maximal inhibition observed at 46% residual CoQ10 of 50-59%. ATP production also decreased by 67.5% in comparison to control. Residual CoQ10 levels of 77% and 46% resulted in an approximately 4x increase in mitochondrial oxidative stress. A 25% decrease in mitochondrial membrane potential was observed at 77% residual CoQ10. Conversely a 40% increase was observed at 46% residual CoQ10 compared to the controls suggesting a possible reversal of ATP synthase (complex V).