The membrane interaction of drugs as one of mechanisms for their enantioselective effects.

The discrimination between different enantiomers of chiral compounds by the biological system is medically important as the pharmacological and toxicological effects of enantiomeric drugs significantly differ depending on their stereostructures. One enantiomer is preferred over its enantiomeric counterpart and a racemic mixture for higher activity or lower toxicity. Such enantioselectivity has been exclusively explained by the stereostructure-specific interactions with receptors, channels and enzymes of drugs including general and local anesthetics, sedatives, hypnotics, anti-inflammatory drugs, analgesics and β-adrenergic antagonists. These drugs can act on not only protein targets but also lipid biomembranes. Almost all of the relevant proteins are embedded in or associated with membrane lipid bilayers. Therefore, we propose one of possible mechanisms that drugs might enantioselectively interact with membrane lipids and induce changes in membrane property like fluidity which are discriminable between enantiomers. If the induced changes are different between enantiomers, enantiomeric drugs would differently influence the membrane lipid environments for receptors, channels and enzymes, resulting in the enantioselectivity of drug effects. The enantioselective membrane interactions of drugs could be mediated by membrane component cholesterol and phospholipids, both of which have chiral centers in structure as well as drug enantiomers. Chiral membrane lipids possibly exhibit the preference for the interactions with drug molecules of either the same chirality or the different chirality, producing the selectivity to one drug enantiomer. The proposed hypothesis may be available to investigate more useful medicines based on the novel concept of drug enantioselectivity.