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. Author manuscript; available in PMC: 2014 Feb 25.
Published in final edited form as: Brain Res. 2012 Dec 1;1497:1–14. doi: 10.1016/j.brainres.2012.11.043

Figure 2.

Figure 2

Inhibition of human liver COMT-mediated O-methylation of L-DOPA by two tea catechins, (+)-catechin and (−)-epicatechin (panels A and B), and a representative flavonoid quercetin (panel C). The incubation mixture consisted of 10 μM L-DOPA, 250 μM [3H-methyl]AdoMet (containing 0.2 μCi), 0.25 mg/mL of human cytosolic protein, 1 mM dithiothreitol, 1.2 mM MgCl2, and a dietary inhibitor (concentration as indicated) in a final volume of 0.25 mL Tris-HCl buffer (10 mM, pH 7.4). Incubations were carried out at 37°C for 10 min. Each point is the mean of duplicate determinations of the 3 human liver (HL) cytosolic samples named HL4C, HL8C and HL9C (with average variations below 5%).