Figure 3.

Concentration-dependent effects of selected phytochemicals on total ATPase activity of digitonin-solubilized rat brain mitochondrial preparations. These compounds include isoflavones (A), flavones (B), catechins (C) and several others (D). Experiments were conducted as in Figure 2. Control experiments indicated that (−)epicatechin-gallate, tannic acid and several flavonoids affected ADP-induced responses, i.e. pyruvate kinase or lactate dehydrogenase; therefore, the total ATPase activity was used here. The inhibition of ADP-induced responses was from 28 to 76% at 70 μM with kaempferol<apigenin<quercetin<(−)epicatechin gallate<morin. This inhibition, however, will not significantly affect the estimation of IC₅₀ for the ATPase since ATP hydrolysis was the limiting step and the residual oligomycin-insensitive ATPase activity is low (13.4 (1.1)% of total activity). ‘NO' indicates the absence of phytochemicals.