title: Optimisation of supercritical carbon dioxide extraction of essential oil of flowers of tea (Camellia sinensis L.) plants and its antioxidative activity.
abstract: BACKGROUND
  To extract natural volatile compounds from tea (Camellia sinensis) flowers without thermal degradation and residue of organic solvents, supercritical fluid extraction (SFE) using carbon dioxide was employed to prepare essential oil of tea flowers in the present study. Four important parameters--pressure, temperature, static extraction time, and dynamic extraction time--were selected as independent variables in the SFE.
  
  
  RESULTS
  The optimum extraction conditions were the pressure of 30 MPa, temperature of 50°C, static time of 10 min, and dynamic time of 90 min. Based on gas chromatography-mass spectrometry analysis, 59 compounds, including alkanes (45.4%), esters (10.5%), ketones (7.1%), aldehydes (3.7%), terpenes (3.7%), acids (2.1%), alcohols (1.6%), ethers (1.3%) and others (10.3%) were identified in the essential oil of tea flowers. Moreover, the essential oil of tea flowers showed relatively stronger DPPH radical scavenging activity than essential oils of geranium and peppermint, although its antioxidative activity was weaker than those of essential oil of clove, ascorbic acid, tert-butylhydroquinone, and butylated hydroxyanisole.
  
  
  CONCLUSIONS
  Essential oil of tea flowers using SFE contained many types of volatile compounds and showed considerable DPPH scavenging activity. The information will contribute to the future application of tea flowers as raw materials in health-care food and food flavour industries.
authors.affiliation: Department of Tea Science, Zhejiang University, 866 Yuhangtang Road, Hangzhou, 310058, China.
authors.forename: Zhenchun
authors.initials: Z
authors.lastname: Chen
authors.forename: Xin
authors.initials: X
authors.lastname: Mei
authors.forename: Yuxia
authors.initials: Y
authors.lastname: Jin
authors.forename: Eun-Hye
authors.initials: EH
authors.lastname: Kim
authors.forename: Ziyin
authors.initials: Z
authors.lastname: Yang
authors.forename: Youying
authors.initials: Y
authors.lastname: Tu
mesh_terms: D000975:Antioxidants / Q000032:analysis / Q000494:pharmacology*; D001713:Biphenyl Compounds / Q000378:metabolism; D028241:Camellia sinensis / Q000737:chemistry*; D025924:Chromatography, Supercritical Fluid / Q000379:methods; D035264:Flowers / Q000737:chemistry*; D008401:Gas Chromatography-Mass Spectrometry; D006801:Humans; D009822:Oils, Volatile / Q000737:chemistry / Q000494:pharmacology*; D010851:Picrates / Q000378:metabolism; D010936:Plant Extracts / Q000737:chemistry / Q000494:pharmacology*; D013662:Tea / Q000737:chemistry; D055549:Volatile Organic Compounds / Q000032:analysis / Q000494:pharmacology*
chemical_list: D000975:Antioxidants; D001713:Biphenyl Compounds; D009822:Oils, Volatile; D010851:Picrates; D010936:Plant Extracts; D013662:Tea; D055549:Volatile Organic Compounds; C004931:1,1-diphenyl-2-picrylhydrazyl
keywords: antioxidative activity; essential oil; supercritical carbon dioxide extraction; tea flower; volatile