The activity of acetylcholinesterase (AChE) from human erythrocytes was tested in the presence of the phenolic compounds resveratrol and epigallocatechin-3-gallate (EGCG). Even though the stilbene barely changed this enzymatic activity, EGCG did inhibit AChE. Importantly, it preferentially acted on the membrane-bound enzyme rather than on its soluble form. Actually, it was shown that this flavonoid may bind to the red blood cell membrane surface, which may improve the interaction between EGCG and AChE. Therefore, caution should be taken when screening AChE inhibitors. In fact, testing compounds with the soluble form of the enzyme may underestimate the activity of some of these potential inhibitors, hence it would be advisable not to use them as a sole model system for screening. Moreover, erythrocyte AChE is proposed as a good model for these enzymatic assays. © 2016 BioFactors, 43(1):73-81, 2017.

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The interaction of enterodiol and the well-described polyphenol epigallocatechin gallate (EGCG) with hepatic membranes has been matter of interest in the last few years. On one hand, EGCG is only able to bind to the phospholipid polar head groups, as it has been already described in synthetic lipid bilayers and erythrocyte membranes but cannot get inserted into the hydrophobic core or be transported into the lumen of membrane vesicles. On the other, enterodiol has no interaction with non-energized membranes either, but it is able to interact and even be transported upon addition of ATP. In fact, the ATPase activity undergoes a twofold increase in the presence of enterodiol but not in the presence of EGCG. This is the first report on the transport of enterodiol by liver membranes, and it may help explain the rather high blood concentrations of this estrogenic enterolignan compared to EGCG, which is extensively metabolized by the intestine and the liver. The present results suggest that a fraction of enterodiol may escape the liver inactivation by being pumped out from the hepatocytes to the bloodstream.