[Role of sterols in the membranotropic activity of triterpene glycosides].

Interaction of stichoposide A, a triterpene glycoside and trepang sterols in solution was studied. With the use of liposomes the binding of the glycoside and its effect on the ion permeability of the lipid membranes of different sterol composition were also studied. It was shown that the membrane activity of the glycoside was defined by the level of its affinity to the sterol receptor. It decreased in the following order: cholesterol, total fraction of delta 5-sterols, total fraction of delta 7-sterols, delta 7-sterol xylosides and delta 5-sterol sulfates. Possible involvement of glycosylated and sulfated forms of sterols in development of resistance in the cell membranes and tissues of trepangs to their own glycosides is discussed.