title: Monoterpenes affect chlorodiazepoxide-micelle interaction through micellar dipole potential modifications.
abstract: The ability of several natural terpenes to affect benzodiazepine (BZD)-micelle interaction through the membrane dipolar organization was investigated. The acid-base equilibrium of chlorodiazepoxide (CDX) and the spectroscopic behavior of the electrochromic dye merocyanine were tested in the presence and in the absence of Triton X-100 micelles (used to mimic a membrane environment) containing or not cineole, menthol, geraniol or camphor. CDX's apparent pK increased in the environment of terpene-containing micelles compared with pure Triton X-100 micelles. Decrements in electric potentials (between -111 and -128 mV with respect to pure detergent) were calculated from Boltzmann equation. This result suggested, that in the presence of terpenes, the tendency of CDXH(+) to remain in the membrane phase increased. The dielectric constant (D) of the microenvironment sensed by merocyanine within Triton X-100 micelles, determined from lambda(max,2) of merocyanine monomer, was D=9 and increased in the presence of all the terpenes assayed (D congruent with 11). The decrease in merocyanine partitioning (A(peak1)/A(peak2) increased) also reflected an increment in the negative dipole potential. The present results suggest that terpenes contributed to the whole dipolar arrangement of the micelle with a dipole moment vector which had an intense component oriented parallel to the intrinsic dipole of the Triton X-100 molecules in the micelles. This led to a more negative environment of the interface region where CDX was located, and increased the net polarity of the deepest micelle regions sensed by merocyanine.
authors.affiliation: Cátedra de Biofísica Química, Depto. de Química, Facultad de Ciencias Exactas, Físicas y Naturales, Universidad Nacional de Córdoba, Av. Velez Sarsfield 1611, X5016CAG Córdoba, Argentina.
authors.forename: Anahí V
authors.initials: AV
authors.lastname: Turina
authors.forename: Anahí V
authors.initials: AV
authors.lastname: del Turina
authors.forename: María A
authors.initials: MA
authors.lastname: Perillo
mesh_terms: D000136:Acid-Base Equilibrium / Q000187:drug effects; D002707:Chlordiazepoxide / Q000378:metabolism*; D008823:Micelles; D039821:Monoterpenes / Q000494:pharmacology*; D017830:Octoxynol / Q000494:pharmacology; D011744:Pyrimidinones; D055672:Static Electricity
chemical_list: D008823:Micelles; D039821:Monoterpenes; D011744:Pyrimidinones; C003954:merocyanine dye; D002707:Chlordiazepoxide; D017830:Octoxynol