An Integrated Metabolomics Study of Glucosinolate Metabolism in Different Brassicaceae Genera.

Hui Zhang,Choon Nam Ong,Yu Liu,Li Zou,Xu Liang,Merja Rossi

doi:10.3390/metabo10080313

Hui Zhang, Choon Nam Ong + Show 4 more

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https://doi.org/10.3390/metabo10080313

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Abstract

Glucosinolates are a group of plant secondary metabolites that can be hydrolyzed into a variety of breakdown products such as isothiocyanates, thiocyanates, and nitriles. These breakdown products can facilitate plant defense and function as attractants to natural enemies of insect pests. As part of the diet, some of these compounds have shown cancer-preventing activities, and the levels of these metabolites in the edible parts of the plants are of interest. In this study, we systematically examined variations in glucosinolates, their precursors, and their breakdown products in 12 commonly consumed vegetables of the Brassicaceae family with gas chromatography—quadrupole time-of-flight mass spectrometer (GC-Q-TOF/MS), liquid chromatography–quadrupole time-of-flight mass spectrometer (LC-Q-TOF/MS), and liquid chromatography—triple quadrupole mass spectrometer (LC-QQQ/MS), using both untargeted and targeted approaches. The findings were integrated with data from literature to provide a comprehensive map of pathways for biosynthesis of glucosinolates and isothiocyanates. The levels of precursor glucosinolates are found to correlate well with their downstream breakdown products. Further, the types and abundances of glucosinolates among different genera are significantly different, and these data allow the classification of plants based on morphological taxonomy. Further validation on three genera, which are grown underground, in damp soil, and above ground, suggests that each genus has its specific biosynthetic pathways and that there are variations in some common glucosinolate biosynthesis pathways. Our methods and results provide a good starting point for further investigations into specific aspects of glucosinolate metabolism in the Brassica vegetables.

Highlights

Glucosinolates are unique and prevalent secondary metabolites found in the order Brassicales [1].This order includes the economically important family Brassicaceae, consisting of many common vegetables such as broccoli, cabbage, Chinese cabbage, radishes, watercress, and rocket [1].Glucosinolates act as precursors for compounds with anti-carcinogenic properties [2]
In order and content varies among families and species [31]. This variation has created a complex picture of to have a biologically meaningful understanding of their metabolism, we summarized the available glucosinolate biosynthesis that is not captured from the literature, which involves a large number published information together with our present findings into a pathway map depicting the of studies published on different aspects of glucosinolate metabolism across genera
Additional details were collected from other relevant literature on glucosinolate. To highlight how such large datasets can be used to better understand glucosinolate metabolism metabolism in Brassicaceae, we further studied three vegetables from different growing environments to illustrate the differences in metabolic profiles across

Summary

Introduction

Glucosinolates are unique and prevalent secondary metabolites found in the order Brassicales [1].This order includes the economically important family Brassicaceae, consisting of many common vegetables such as broccoli, cabbage, Chinese cabbage, radishes, watercress, and rocket [1].Glucosinolates act as precursors for compounds with anti-carcinogenic properties [2]. Glucosinolates are unique and prevalent secondary metabolites found in the order Brassicales [1]. This order includes the economically important family Brassicaceae, consisting of many common vegetables such as broccoli, cabbage, Chinese cabbage, radishes, watercress, and rocket [1]. Glucosinolates act as precursors for compounds with anti-carcinogenic properties [2]. Epidemiological studies show that a diet rich in broccoli and other cruciferous vegetables reduces the risk of cancer [3,4,5,6,7]. Glucosinolate breakdown pathways are known to have protective roles in both abiotic and biotic stress. Endogenous β-glucosidases, called myrosinase enzymes, get mixed with the glucosinolates in the cell, hydrolyzing the thioglucosidic bond [8]. The reaction can form isothiocyanates, which can be converted into nitriles, epithionitriles, or organic thiocyanates

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