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It was found that complexes of the flavonoids quercetin, taxifolin, catechin and morin with divalent iron initiated an increase in light scattering in a suspension of unilamellar 100nm liposomes. The concentration of divalent iron in the suspension was 10μM. Liposomes were prepared from 1-palmitoyl-2-oleoylglycero-3-phoshpatidylcholine. The fluorescent resonance energy transfer (FRET) analysis of liposomes labeled with NBD-PE and lissamine rhodamine B dyes detected a slow lipid exchange in liposomes treated with flavonoid-iron complexes and calcium, while photon correlation spectroscopy and freeze-fracture electron microscopy revealed the aggregation and fusion of liposomes to yield gigantic vesicles. Such processes were not found in liposomes treated with phloretin because this flavonoid is unable to interact with iron. Rutin was also unable to initiate any marked changes because this water-soluble flavonoid cannot interact with the lipid bilayer. The experimental data and computer calculations of lipophilicity (cLogP) as well as the charge distribution on flavonoid-iron complexes indicate that the adhesion of liposomes is provided by an iron link between flavonoid molecules integrated in adjacent bilayers. It is supposed that calcium cations facilitate the aggregation and fusion of liposomes because they interact with the phosphate moieties of lipids., (Copyright © 2011 Elsevier B.V. All rights reserved.)

The effects of triterpenoid glycosides from Korean red ginseng Panax C.A. Meyer and their aglycons on the phase transitions of model DPPC membranes were studied by microcalorimetry. Glycosides Rb1, Rg1, 20(S) protopanaxadiol only slightly interacted with the DPPC gel phase and caused no formation of new phases. At concentrations close to equimolar values, the glycosides slightly disturbed the packing of lipids and induced the formation of the second phases with more dense lipid packing but smaller sizes of the cooperative domains as compared with pure lipid. Cholesterol (3%) produced no effect on the DPPC interaction with Rb1, Rg1 and panaxatriol but affected the DPPC interaction with panaxadiol. At equimolar panaxadiol/DPPC ratio and in the presence of 3% cholesterol, panaxadiol completely eliminated the main transition.

The mechanisms of action of total saponins from Panax Ginseng C.A. Meyer on the elements of intracellular signalling system in Ehrlich ascites tumor cells were studied. The action of total saponins was compared with the effect of ATP, a classical activator of these cells. Saponins at concentrations of 10(-6)-10(-3)% increased [Ca2+]i, mobilized Ca2+ ions from the endoplasmic reticulum (ER) and activated the influx of Ca2+ to cells. Like ATP, saponins activated the Na+/H+ exchange and Ca(2+)-dependent K+ channels. Of all the parameters, only the activation of Ca2+ influx in cell is directly affected by saponins. The changes in other parameters are connected with nonspecific activation of purinoreceptors. The analysis of the kinetic data suggests that, as distinct from ATP-dependent activation of purinoreceptor, saponins first activate the Ca2+ influx to cells and only then induce the mobilization of Ca2+ from ER.

The influence of dammaran triterpene glycosides (ginsenosides Rb1 and Rg1) from Panax Ginseng C.A. Meyer and their aglycones on the phase transfers of multilayer vesicles of dipalmitoylphosphatidyl choline was studied. Ginsenosides Rb1 and Rg1 and aglycone 20(S) protopanaxatriol insignificantly modified the lipid gel phase and only in concentrations close to the equimolar ones insignificantly damaged the lipid covers and decreased the size of the cooperative unit. Aglycone 20(S) protopanaxadiol (PD) induced the formation of the second phase with a more solid cover of the lipids but a lower size of the cooperative unit by comparison with that of the pure lipid. The presence of cholesterol in an amount up to 5 mol per cent slightly influenced the interaction of the agents with the gel phase except for PD. In the presence of cholesterol PD did not induce the formation of the two phases and in an amount of 100 mol per cent eliminated the major transfer. The study suggested that PD interacted with the gel phase and did not penetrate into the bilayer deeper than the glycerol skeleton of the lipid molecule.

The action of the dammarane triterpene glycosides Rb1 and Rg1 and their aglycones 20(S) protopanaxatriole and 20(S) protopanaxadiole from Korean ginseng on permeability of bilayer lipid membranes formed of monolayers was studied. RgI, protopanaxatriole and protopanaxadiole in concentrations of 3, 0.5 and 30 micrograms/ml respectively formed single ionic channels in the water phase on the membrane side containing cholesterol. The channel conductivity was 5 to 30 pSm in 1 M KCl. The ionic channels were more selective with respect to K+ as compared to Cl-. Rb1 was also able to increase the conductivity of the lipid membranes. However, no jumps in the current characteristics of the single channels were detected. All the substances in high concentrations on one side of the membrane independently of the cholesterol content induced fluctuation of the high amplitude current (from several tens of pSm to several hundreds of nSm).

The influence of the dammarane triterpene glycosides Rb1, Rb2, Rg1 and Rf and their aglycones 20(S) protopanaxatriol and 20(S) protopanaxadiol on fluctuation of the K+ and H+ flows in erythrocytes induced by ionophore A23187 and Ca2+ was studied. It was shown that glycoside Rb1 (10 to 50 micrograms/ml) and 20(S) protopanaxatriol (30 micrograms/ml) had a property of inducing fluctuation of the K+ and H+ flows in erythrocytes. In case of Rb1 the system entirely reversed to the initial state whereas in case of the protopanaxatriol use after the fluctuation the system did not reverse to the initial state. Glycosides Rb2 (10 to 30 micrograms/ml), Rg1 (5 to 20 micrograms/ml) and Rf (10 to 100 micrograms/ml) and 20(S) protopanaxadiol (30 micrograms/ml) in the concentrations used did not initiate the fluctuations. The above substances increased the extracellular concentration of K+ and pH without the system reversion to the initial state.

Molecular mechanisms of action of the total fraction of saponins from Red Korean Ginseng on the elements of the intracellular signalling system of the cells of ascitic Ehrlich carcinoma (AEC) were studied. The action of the total fraction of the saponins on the AEC cells was compared with that of the classic activator of such cells i.e. ATP. It was shown that the action of the total fraction of the saponins was similar to that of ATP. In concentrations of 10(-6) to 10(-3) per cent saponin induced an increase of [Ca2+]j mobilizing Ca2+ from the endoplasmic reticulum (ER) and activating the Ca2+ inlet to the cells. The same as in case with the use of ATP the Ca2+ mobilization from ER was reversible. In comparison to ATP saponin induced higher activation of the Ca2+ inlet to ER and the cells. The same as ATP saponin activated the Na+/H+ exchange and the Ca2+ - dependent K+-channels. Out of all the mention-ed parameters only the activation of the Ca2+ inlet to the cells was probably the direct result of the saponin action. The changes in the other parameters were mediated by nonspecific activation of the purine receptor. The analysis of the kinetic data demonstrated that unlike the ATP-dependent activation of the purine receptor the saponins first of all activated the inlet of Ca2+ to the cells and only after that the mobilization of the latter from ER.