(A) Concentration-response results of compounds 6, 7, 10, and 24 on oxygen consumption by T47D cells (mean ± SD, three independent experiments). The compounds were tested at 1, 3, 10, and 30 μM. An asterisk (*) indicates statistically significant difference (p < 0.05) between the control and the compound treated sample, compared by one-way ANOVA and Bonfferoni post hoc analyses (GraphPad Prism 4.0). (B) Compound 6 (10 μM) did not affect mitochondrial electron transport chain (ETC) complex II, III, or IV. Substrates and inhibitors were added to T47D cells (5 × 106, 30 °C) in a sequential manner at the specified time point. (C) Compound 7 (10 μM) did not affect ETC complex II, III, or IV. (D) Compound 6 (10 μM) suppressed mitochondria respiration by inhibiting complex I. (E) Compound 7 (10 μM) inhibited complex I.