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Published on: January 7, 2019
Quantitative metabolite profiling of edible onion species by NMR and HPLC-MS
Tuula H Soininen1, Niko Jukarainen1, Seppo O K Auriola2
1School of Pharmacy, Biocenter Kuopio, University of Eastern Finland, Kuopio, Finland.
Abstract:
Allium genus is a treasure trove of valuable bioactive compounds with potentially therapeutically important properties. This work utilises HPLC-MS and a constrained total-line-shape (CTLS) approach applied to (1)H NMR spectra to quantify metabolites present in onion species to reveal important inter-species differences. Extensive differences were detected between the sugar concentrations in onion species. Yellow onion contained the highest and red onion the lowest amounts of amino acids. The main flavonol-glucosides were quercetin 3,4'-diglucoside and quercetin 4'-glucoside. In general, the levels of flavonols were, higher in yellow onions than in red onions, and garlic and leek contained a lower amount of flavonols than the other Allium species. Our results highlight how (1)H NMR together with HPLC-MS can be useful in the quantification and the identification of the most abundant metabolites, representing an efficient means to pinpoint important functional food ingredients from Allium species.
Insights
This study quantifies bioactive compounds in Allium species using HPLC-MS and NMR. Yellow onions show higher flavonol and amino acid levels than red onions, highlighting functional food potential.
Area of Science:
- Agricultural Science
- Biochemistry
- Nutritional Science
Background:
- The Allium genus, encompassing onions, garlic, and leeks, is rich in bioactive compounds with therapeutic potential.
- Understanding the metabolic profiles of different Allium species is crucial for identifying valuable functional food ingredients.
Purpose of the Study:
- To quantify and identify key metabolites in various Allium species.
- To investigate inter-species differences in metabolite concentrations, particularly sugars, amino acids, and flavonols.
- To evaluate the utility of High-Performance Liquid Chromatography-Mass Spectrometry (HPLC-MS) and Nuclear Magnetic Resonance (NMR) spectroscopy for metabolite profiling.
Main Methods:
- Utilized High-Performance Liquid Chromatography-Mass Spectrometry (HPLC-MS) for metabolite separation and detection.
- Applied a constrained total-line-shape (CTLS) approach to (1)H Nuclear Magnetic Resonance ((1)H NMR) spectra for metabolite quantification.
- Analyzed metabolite profiles across different onion species, as well as garlic and leek.
Main Results:
- Significant inter-species variations in sugar concentrations were observed among Allium species.
- Yellow onions exhibited the highest concentrations of amino acids, while red onions had the lowest.
- Quercetin 3,4'-diglucoside and quercetin 4'-glucoside were identified as the primary flavonol-glucosides.
- Yellow onions generally contained higher flavonol levels compared to red onions; garlic and leek had lower flavonol content than other Allium species.
Conclusions:
- (1)H NMR combined with HPLC-MS provides an efficient method for quantifying and identifying abundant metabolites in Allium species.
- The study highlights significant metabolic differences between Allium species, particularly in flavonol and amino acid content.
- These findings underscore the potential of Allium species, especially yellow onions, as sources of important functional food ingredients.
