Conventional and accelerated-solvent extractions of green tea (camellia sinensis) for metabolomics-based chemometrics

Joshua J Kellogg,Emily D Wallace,Tyler N Graf,Nicholas H Oberlies,Nadja B Cech

doi:10.1016/j.jpba.2017.07.027

Joshua J Kellogg, Emily D Wallace + Show 3 more

Open Access

https://doi.org/10.1016/j.jpba.2017.07.027

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Abstract

Metabolomics has emerged as an important analytical technique for multiple applications. The value of information obtained from metabolomics analysis depends on the degree to which the entire metabolome is present and the reliability of sample treatment to ensure reproducibility across the study. The purpose of this study was to compare methods of preparing complex botanical extract samples prior to metabolomics profiling. Two extraction methodologies, accelerated solvent extraction and a conventional solvent maceration, were compared using commercial green tea [Camellia sinensis (L.) Kuntze (Theaceae)] products as a test case. The accelerated solvent protocol was first evaluated to ascertain critical factors influencing extraction using a D-optimal experimental design study. The accelerated solvent and conventional extraction methods yielded similar metabolite profiles for the green tea samples studied. The accelerated solvent extraction yielded higher total amounts of extracted catechins, was more reproducible, and required less active bench time to prepare the samples. This study demonstrates the effectiveness of accelerated solvent as an efficient methodology for metabolomics studies.

Highlights

Metabolomics has developed into an important tool in analyzing large datasets, including those related to disease biomarkers [1], food quality [2], and natural products discovery [3], [4]
Robust and reproducible techniques for sample extraction are imperative for reliable metabolomics investigations
Ultraperformance liquid chromatography − mass spectrometry (UPLC–MS) data were acquired using a Q Extractive Plus quadrupole-orbitrap mass spectrometer (Thermo Fisher Scientific) with an electrospray ionization source coupled to an Acquity UPLC system (Waters, Milford, MA, USA)

Summary

Introduction

Metabolomics has developed into an important tool in analyzing large datasets, including those related to disease biomarkers [1], food quality [2], and natural products discovery [3], [4]. Conventional sample preparation techniques require multiple steps involving solid and liquid transfer [7], and can account for up to one-third of the error of the overall analytical procedure [8]. Accelerated-solvent extraction (ASE, known as pressurized liquid extraction (PLE)) has been touted as a reliable and efficient method of metabolite extraction [9]. High pressure keeps organic solvents in a liquid phase, even at elevated temperatures, and assists in permeation of the solvent through the sample matrix, maximizing contact with the analyte and facilitating effective extraction [10]. The automation of accelerated solvent extractions increases its efficiency and reproducibility, and ASE has become a commonly employed tool for extraction of pesticides from environmental samples [11], food or supplement contaminants [12], and supplement or dietary nutraceuticals [13]. This technique is not widely employed in natural products chemistry investigations, which tend to rely on more traditional benchtop extraction methodologies

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