title: Extraction of thymol from different varieties of thyme plants using green solvents.
abstract: BACKGROUND
  Thymol (2-isopropyl-5-methylphenol) is the main monoterpene phenol found in thyme essential oil. This compound has revealed several biological properties, including antibacterial, anti-inflammatory and antioxidant activities. In this work, a comparison was made between the performance of different green solvents (ethanol, limonene and ethyl lactate), by pressurized liquid extraction (PLE) and supercritical fluid extraction (SFE) at different conditions, to extract thymol from three different varieties of thyme (Thymus vulgaris, Thymus zygis and Thymus citriodorus). Additionally, new solubility data of thymol in limonene and ethanol at ambient pressure and temperatures in the range 30-43 °C are reported.
  
  
  RESULTS
  The highest thymol recoveries were attained with T. vulgaris (7-11 mg g(-1)). No thymol could be quantified in the PLE samples of T. citriodorus. The highest concentrations of thymol in the extracts were obtained with limonene. Thymol is very soluble in both solvents, particularly in ethanol (∼900 mg g(-1) at ∼40 °C), and is the main compound (in terms of peak area) present in the essential oil extracts obtained.
  
  
  CONCLUSIONS
  The three solvents show good capacity to extract thymol from T. vulgaris and T. zygis by PLE. Although PLE proved to be a suitable technology to extract thymol from thyme plants, the highest concentrations of thymol were obtained by SFE with supercritical CO2 .
authors.affiliation: Instituto de Investigación en Ciencias de la Alimentación CIAL (CSIC-UAM), CEI UAM + CSIC, Universidad Autónoma de Madrid, C/Nicolás Cabrera 9, E-28049, Madrid, Spain.
authors.forename: David
authors.initials: D
authors.lastname: Villanueva Bermejo
authors.affiliation: Institute of Chemical Engineering, Bulgarian Academy of Sciences, 1113 Sofia, Bulgaria.
authors.forename: Ivan
authors.initials: I
authors.lastname: Angelov
authors.affiliation: Instituto de Investigación en Ciencias de la Alimentación CIAL (CSIC-UAM), CEI UAM + CSIC, Universidad Autónoma de Madrid, C/Nicolás Cabrera 9, E-28049, Madrid, Spain.
authors.forename: Gonzalo
authors.initials: G
authors.lastname: Vicente
authors.affiliation: Institute of Chemical Engineering, Bulgarian Academy of Sciences, 1113 Sofia, Bulgaria.
authors.forename: Roumiana P
authors.initials: RP
authors.lastname: Stateva
authors.affiliation: Instituto de Investigación en Ciencias de la Alimentación CIAL (CSIC-UAM), CEI UAM + CSIC, Universidad Autónoma de Madrid, C/Nicolás Cabrera 9, E-28049, Madrid, Spain.
authors.forename: Mónica
authors.initials: M
authors.lastname: Rodriguez García-Risco
authors.affiliation: Instituto de Investigación en Ciencias de la Alimentación CIAL (CSIC-UAM), CEI UAM + CSIC, Universidad Autónoma de Madrid, C/Nicolás Cabrera 9, E-28049, Madrid, Spain.
authors.forename: Guillermo
authors.initials: G
authors.lastname: Reglero
authors.affiliation: Instituto de Investigación en Ciencias de la Alimentación CIAL (CSIC-UAM), CEI UAM + CSIC, Universidad Autónoma de Madrid, C/Nicolás Cabrera 9, E-28049, Madrid, Spain.
authors.forename: Elena
authors.initials: E
authors.lastname: Ibañez
authors.affiliation: Instituto de Investigación en Ciencias de la Alimentación CIAL (CSIC-UAM), CEI UAM + CSIC, Universidad Autónoma de Madrid, C/Nicolás Cabrera 9, E-28049, Madrid, Spain.
authors.forename: Tiziana
authors.initials: T
authors.lastname: Fornari
mesh_terms: D025924:Chromatography, Supercritical Fluid; D053138:Cyclohexenes / Q000737:chemistry*; D000431:Ethanol / Q000737:chemistry*; D007773:Lactates / Q000737:chemistry*; D000077222:Limonene; D009822:Oils, Volatile / Q000737:chemistry*; D010936:Plant Extracts / Q000737:chemistry; D011312:Pressure; D012995:Solubility; D012997:Solvents / Q000737:chemistry*; D013045:Species Specificity; D013729:Terpenes / Q000737:chemistry*; D013943:Thymol / Q000737:chemistry / Q000302:isolation & purification*; D046930:Thymus Plant / Q000737:chemistry* / Q000235:genetics
chemical_list: D053138:Cyclohexenes; D007773:Lactates; D009822:Oils, Volatile; D010936:Plant Extracts; D012997:Solvents; D013729:Terpenes; D013943:Thymol; D000431:Ethanol; D000077222:Limonene; C015866:ethyl lactate
keywords: ethyl lactate; limonene; pressurized liquid extraction (PLE); supercritical fluid extraction (SFE); thyme