Lupane type triterpenes as structuring elements in the monolayers and films of lecithin and fullerene derivatives

Abstract

Using compression and wetting isotherm analysis, it was shown that lupane triterpenes (betuli nol, betulinol diacetate, betulinic acid) change crucially the state of monolayers and films of C 60 fullerene, nitroxide malonate C 60 methanofullerene, and lecithin and also the films of their mixtures at the water-air interface. The structuring action of triterpenes in the presence of lecithin and C 60 fullerene at high triterpene contents in the film gives rise to uniaxially oriented films similar to thin films of triterpenes (atomic force microscopy data). The formation of mixed bis nitroxide malonate methanofullerene-triterpene films with excess of the latter affords structures shaped like crater like bowls.The lupane triterpenes possess valuable biological prop erties including antitumor, anti HIV 1, antibacterial, an tiinflammatory, and hepatoprotector activities. 1-5 As re gards their chemical nature and the hydrophilic lipophilic balance, triterpenes, for example, betulinol (1), betulinol diacetate (2), and betulinic acid (3), are close to another class of polycyclic saturated hydrocarbons, lipophilic ste rols (such as cholesterol).R 1 = OH, R 2 = CH 2 OH (1); R 1 = OAc, R 2 = CH 2 OAc (2); R 1 = OH, R 2 = COOH (3) The role of lipophilic triterpenes is most often a de crease in the attraction forces between the lipid hydrocar bon chain, thus inducing cooperative interactions in the membrane and finally controlling its fluidity. 6 The stabilization mechanism of biomembranes by triterpenes is based on aggregation, structurization, and clusteriza tion in the systems triterpene-lipophilic physiologically active compounds.The effect of lipophilic physiologically active com pounds was studied in relation to C 60 fullerene, bis ni troxide malonate C 60 methanofullerene (4), and leci thin. Currently C 60 fullerene and its derivatives are known as components of pharmaceutical drugs with a broad spectrum of physiological action. 7,8 The high lipophilicity of fullerene fragment allows the complex es and aggregates formed to penetrate into almost all tissues including the brain. High lipophilicity of fullerene derivatives and their aggregation complexes with physiologically active substances determines, in particu lar, the membranotropic mechanism of their antiviral action. 7