Abstract
A total of 13 anthocyanins and 33 metabolites; including organic acids, phenolic acids, amino acids, organic compounds, sugar acids, sugar alcohols, and sugars, were profiled in three radish cultivars by using high-performance liquid chromatography (HPLC) and gas chromatography time-of-flight mass spectrometry (GC-TOFMS)-based metabolite profiling. Total phenolics and flavonoids and their in vitro antioxidant activities were assessed. Pelargonidins were found to be the major anthocyanin in the cultivars studied. The cultivar Man Tang Hong showed the highest level of anthocyanins (1.89 ± 0.07 mg/g), phenolics (0.0664 ± 0.0033 mg/g) and flavonoids (0.0096 ± 0.0004 mg/g). Here; the variation of secondary metabolites in the radishes is described, as well as their association with primary metabolites. The low-molecular-weight hydrophilic metabolite profiles were subjected to principal component analysis (PCA), hierarchical clustering analysis (HCA), Pearson’s correlation analysis. PCA fully distinguished the three radish cultivars tested. The polar metabolites were strongly correlated between metabolites that participate in the TCA cycle. The chemometrics results revealed that TCA cycle intermediates and free phenolic acids as well as anthocyanins were higher in the cultivar Man Tang Hong than in the others. Furthermore; superoxide radical scavenging activities and 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging were investigated to elucidate the antioxidant activity of secondary metabolites in the cultivars. Man Tang Hong showed the highest superoxide radical scavenging activity (68.87%) at 1000 μg/mL, and DPPH activity (20.78%), followed by Seo Ho and then Hong Feng No. 1. The results demonstrate that GC-TOFMS-based metabolite profiling, integrated with chemometrics, is an applicable method for distinguishing phenotypic variation and determining biochemical reactions connecting primary and secondary metabolism. Therefore; this study might provide information on the relationship between primary and secondary metabolites and a synergistic antioxidant ability derived from the secondary metabolites in the radish cultivars.
Highlights
Radish (Raphanus sativus L.), a member of the Cruciferae family, is a root vegetable crop, cultivated and consumed around the world [1]
high-performance liquid chromatography (HPLC) analysis revealed that pelargonidins were the major anthocyanidins in the radish cultivars, since among a total of 13 anthocyanins detected, 12 were pelargonidin-based, whereas one was a cyanidin-based anthocyanin derivative (Table 1)
The results of the correlation and principal component analysis (PCA) analyses showed that the TCA cycle intermediates and phenolic acids were found at relatively higher levels in Mang Tang Hong than in the other cultivars
Summary
Radish (Raphanus sativus L.), a member of the Cruciferae family, is a root vegetable crop, cultivated and consumed around the world [1]. Metabolic profiling involves systematic phenotyping analysis to obtain information on the quantitative low-molecular-weight metabolites present in a biological system in order to comprehensively describe a variety of biological phenomena in combination with genome-wide gene-expression arrays This is accompanied by the measurement of a broad range of metabolites including amino acids, organic acids, sugars, TCA intermediates, bile acids, simple fatty acids, and oligopeptides [21,22]. Gas chromatography mass spectrometry (GC-MS) is a multidimensional analytical technique used for metabolic profiling It has long been utilized in various fields of biological science and enables the identification and quantification of diverse metabolites in a single plant. A comprehensive interpretation of primary and secondary metabolites in red radish cultivars using HPLC analysis and GC-TOFMS-based metabolic profiling combined with chemometrics has not been published. We studied SOD-like activities, and DPPH radical scavenging was employed to identify the relationship between the antioxidant capacity and the natural products
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