title: Molecular dynamics and partitioning of di-tert-butyl nitroxide in stratum corneum membranes: effect of terpenes.
abstract: In this work, we have used electron paramagnetic resonance (EPR) spectroscopy of the small spin label di-tert-butyl nitroxide (DTBN), which partitions the aqueous and hydrocarbon phases, to study the interaction of the terpenes alpha-terpineol, 1,8-cineole, L(-)-carvone and (+)-limonene with the uppermost skin layer, the stratum corneum, and the membrane models of 1,2-dipalmitoyl-sn-glycero-3-phosphatidylcholine (DPPC) and 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC). The EPR spectra indicated that the terpenes increase both the partition coefficient and the rotational correlation time of the spin labels in the stratum corneum membranes, whereas similar effects were observed in the DMPC and DPPC bilayers only at temperatures below the liquid-crystalline phase. The EPR parameter associated to probe polarity inside the membranes showed thermotropically induced changes, suggesting relocations of spin probe, which were dependent on the membrane phases. While the DMPC and DPPC bilayers showed abrupt changes in the partitioning and rotational correlation time parameters in the phase transitions, the SC membranes were characterized by slight changes in the total range of measured temperatures, presenting the greatest changes or membranes reorganizations in the temperature range of approximately 50 to approximately 74 degrees C. The results suggest that terpenes act as spacers, weakening the hydrogen-bonded network at the polar interface and thus fluidizing the stratum corneum lipids.
authors.affiliation: Instituto de Física, Universidade Federal de Goiás, Goiânia, GO 74001-970, Brazil.
authors.forename: Heverton Silva
authors.initials: HS
authors.lastname: Camargos
authors.forename: Adolfo Henrique Moraes
authors.initials: AH
authors.lastname: Silva
authors.forename: Jorge Luiz Vieira
authors.initials: JL
authors.lastname: Anjos
authors.forename: Antonio
authors.initials: A
authors.lastname: Alonso
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D002073:Butanes / Q000493:pharmacokinetics* / Q000494:pharmacology; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism; D004578:Electron Spin Resonance Spectroscopy; D006838:Hydrocarbons / Q000737:chemistry; D056004:Molecular Dynamics Simulation; D015394:Molecular Structure; D051381:Rats; D017208:Rats, Wistar; D012867:Skin / Q000187:drug effects / Q000378:metabolism*; D012869:Skin Absorption; D013729:Terpenes / Q000493:pharmacokinetics* / Q000494:pharmacology; D014867:Water / Q000737:chemistry
chemical_list: D002073:Butanes; D006838:Hydrocarbons; D013729:Terpenes; D014867:Water; C007539:di-t-butyl nitroxide