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Anal Bioanal Chem (2013) 405:50055011 DOI 10.1007/s00216-013-6869-2
TRENDS
Metabolomics for unknown plant metabolites
Ryo Nakabayashi & Kazuki Saito
Received: 30 January 2013 /Revised: 20 February 2013 /Accepted: 25 February 2013 /Published online: 27 March 2013 # Springer-Verlag Berlin Heidelberg 2013
Abstract In this article we discuss current trends in the techniques available for plant metabolomics. Chemical assignment of unknown metabolites leads to understanding of biosynthetic mechanisms at the gene level for genome-sequenced plants. Metabolomics using mass spectrometry has achieved innovative results in phytochemical genomics for primary and secondary metabolism in the model plant Arabidopsis thaliana by using publicly and commercially available information and standard compounds. However, finding a consolidated analytical technique for elucidation of structural information (e.g., elemental composition and structure) remains challenging. Recently, hyphenated analytical techniques and computer-assisted structural analysis with high-throughput and high-accuracy have been developing. Metabolite-driven approaches using such technology will be of central importance in phytochemical genomics.
Keywords Metabolomics . Unknown secondary metabolites . LCMS . LCSPENMRMS .Computer-assisted structure elucidation
Introduction
Plant secondary metabolites (or specialized metabolites) have been studied since the isolation of morphine in the early
19th century [1]. Continued research has revealed the vast array and structural diversity of secondary metabolites in plants. These metabolites are purified by use of conventional techniques, for example recrystallization and chromatography, and their structures are elucidated by combinatorial physicochemical data, including appearance, melting point, specific optical rotation, circular dichroism (CD), ultraviolet (UV), infrared (IR), and nuclear magnetic resonance (NMR) spectroscopy, and mass spectrometry (MS) (Fig. 1). These metabolites can have unique structures, simple or complicated, often with strong biological activity for health promotion. This is particularly evident in newly approved drugs [2] and pesticides [3], as these are mainly composed or derived from secondary metabolites.
Phytochemical genomics have revealed biosynthetic mechanisms at gene to metabolite levels in plants. Arabidopsis thaliana (Arabidopsis) has been central to many studies [4]. In Arabidopsis, metabolites and genes involved in biosynthetic pathways of phenylpropanoids, flavonoids, glucosinolates, terpenoids, and lipids have been identified by use of approaches such as omics (e.g., metabolomics and transcriptomics) [5, 6]. Information about phytochemical genomics is expected to be applicable to crop breeding [7] and pharmaceutical science [8] for enhancement of secondary metabolite production. The appearance of advanced genome sequencers has given us...