Hyperici herba extract interaction with artificial lipid bilayers

Hyperici herba (Hyp) is the aerial part collected during the flowering period from the well-known herb, Hypericum perforatum. Black lipid membrane experiments were performed to investigate the effect of the ethanolic Hyp extract on the electrical properties (capacitance and conductance) of artificial lipid bilayers. Hyp extract (1-10 microg mL(-1)) induced a concentration-dependent increase of both specific transmembrane capacitance and conductance in phosphatidylcholine (PC) membranes. The effect on conductance was enhanced when the Hyp extract (3 microg mL(-1)) was present on both sides of the membrane (Gm=77.89 +/- 8.81 nS cm(-2), n=5) compared with single-sided application (Gm=36.48 +/- 2.41 nS cm(-2), n=5). In bilayers containing PC and phosphatidylserine (PS), PC:PS, the Hyp extract effect was greater than on pure PC bilayers, although the surface charge was not the determining factor of this enhanced activity. Adding cholesterol to the PC:PS mixture reverted the conductance increase induced by the Hyp extract in a dose-dependent manner. The specific pattern of the Hyp extract interaction with lipid bilayers has possible consequences concerning its absorption and bioavailability, as well as its pharmacodynamic effects on neuronal excitability.