A spin label study of the interaction of biologically active terpenes with model membranas.

TURINA A. DEL V.; CLOP E,M; PERILLO M.A.; SCHREIER S.

Hotel Panamericano - San Carlos de Bariloche, Rio Negro

Congreso; XXXII Reunión Anual de la Sociedad Argentina de Biofísica; 2003

Terpenes exert a variety of biological activities. We have investigated the interaction between a series of terpenes (cineol, geraniol, thymol, menthol, and camphor) and phospholipid (in the absence and presence of 25 mole% cholesterol) model membranes by means of spin labeling EPR. EPR spectra of incorporated lipid spin probes (doxyl derivatives of stearic acid carrying the nitroxide moiety at carbons 5, 5-SASL, and 12, 12-SASL) were obtained as a function of terpene concentration. The spectra indicated that the degree of molecular freedom of the probes increased with increasing terpene concentration until a saturation state was obtained. Saturation was ascribed to the achievement of the solubility of the compounds in aqueous solution. It was found that the different molecules affected molecular motion to a different extent, probably due to the contribution of intrinsic differences in chemical structure and to the degree of partitioning in the model membranes. In addition, all terpenes except for camphor, formed micelle-like aggregates at enough concentrations. At these concentrations, in the presence of membranes, the compounds were able to form mixed terpene:phospholipid micelles.