title: Extraction for metabolomics: access to the metabolome.
abstract: BACKGROUND
  The value of information obtained from a metabolomic study depends on how much of the metabolome is present in analysed samples. Thus, only a comprehensive and reproducible extraction method will provide reliable data because the metabolites that will be measured are those that were extracted and all conclusions will be built around this information.
  
  
  OBJECTIVE
  To discuss the efficiency and reliability of available sample pre-treatment methods and their application in different fields of metabolomics.
  
  
  METHODS
  The review has three sections: the first deals with pre-extraction techniques, the second discusses the choice of extraction solvents and their main features and the third includes a brief description of the most used extraction techniques: microwave-assisted extraction, solid-phase extraction, supercritical fluid extraction, Soxhlet and a new method developed in our laboratory--the comprehensive extraction method.
  
  
  RESULTS
  Examination of over 200 studies showed that sample collection, homogenisation, grinding and storage could affect the yield and reproducibility of results. They also revealed that apart from the solvent used for extraction, the extraction techniques have a decisive role on the metabolites available for analysis.
  
  
  CONCLUSIONS
  It is essential to evaluate efficacy and reproducibility of sample pre-treatment as a first step to ensure the reliability of a metabolomic study. Among the reviewed methods, the comprehensive extraction method appears to provide a promising approach for extracting diverse types of metabolites.
authors: Natural Products Laboratory, Institute of Biology, Leiden University, 2300 RA, Leiden, The Netherlands.
authors: Mian Yahya
authors: MY
authors: Mushtaq
authors: Young Hae
authors: YH
authors: Choi
authors: Robert
authors: R
authors: Verpoorte
authors: Erica G
authors: EG
authors: Wilson
mesh_terms: D055432:Metabolomics; D008872:Microwaves; D015203:Reproducibility of Results; D012997:Solvents; D013696:Temperature
chemical_list: D012997:Solvents
keywords: Extraction; metabolomics; sample pre-treatment