Polar Lipids in Starch-Rich Commodities to be Analyzed with LC-MS-Based Metabolomics-Optimization of Ionization Parameters and High-Throughput Extraction Protocols.

Christin Claassen,Sascha Rohn,Jürgen Kuballa

doi:10.3390/metabo9080167

Abstract

Metabolomics-based approaches are still receiving growing attention with regard to food authenticity testing. Such studies require enormous sample numbers with negligible experimental or analytical variations to obtain statistically reliable results. In this context, an extraction protocol in line with optimized ionization parameters was developed in consideration of potential starch-derived matrix effects focusing on the polar lipids of potatoes. Therefore, well-known extractions (Bligh and Dyer, Folch, Matyash, and a n-hexane-based procedure) were compared in a non-targeted and a targeted approach regarding the extractability of their lipids such as phosphatidylcholines, phosphatidylethanolamines, galacto- and glucocerebrosides, di- and triglycerides, and acylated steryl glucosides. The selected Folch method was also scrutinized in view of its ability to remove the matrix’s starch and consequently improved by substituting trichlormethane with ethyl acetate as a “greener” Folch approach. Moreover, the challenge of starch-derived contamination and imminent ion suppression in the electrospray ionization source (ESI) was addressed by an optimization of ionization parameters varying desolvation settings, removing injection peaks, and increasing the angles and distances of the ESI-device. Long-term stability tests over five days were performed successfully with a combination of appropriate extraction and decreased desolvation settings during ionization. In conclusion, the present methodology provided the basis for on-going large-scale metabolomic studies with respect to the botanical origin of potatoes using UPLC-IMS-QToF (ultra-high performance liquid chromatography ion mobility spectroscopy quadrupole-time of flight mass spectrometer).

Highlights

The plant metabolome, a complement of cellular metabolites, mirrors cell activities at a functional level
Comparison of Extraction Procedures lipophilic substances, in particular procedures according to Bligh and Dyer [22], Folch [23], Matyash
For in theparticular comparison of extraction yields, dimensions were reduced, andMatyash varietal [24], differences substances, procedures according to Bligh and Dyer

Summary

Introduction

The plant metabolome, a complement of cellular metabolites, mirrors cell activities at a functional level. The comprehension of metabolic compositions can thereby be considered as a tool in modeling intra- and intercellular biological pathways [1]. Metabolic fingerprinting, as a non-targeted approach which detects as many metabolites as possible without necessarily identifying or quantifying them, is often conducted [2]. An appropriate statistical evaluation of metabolomic experiments requires data sets with enormous sample numbers. Any experimental and instrumental variations must be reduced to a minimum in order to focus on the biological information of importance [3].

Methods

Results

Discussion

Conclusion