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Metabolite Profiling of Leek (Allium porrum L) Cultivars by ¹H NMR and HPLC–MS

Soininen, Tuula H., Jukarainen, Niko, Soininen, Pasi, Auriola, Seppo O. K., Julkunen‐Tiitto, Riitta, Oleszek, Wieslaw, Stochmal, Anna, Karjalainen, Reijo O., Vepsäläinen, Jouko J.
Phytochemical analysis 2014 v.25 no.3 pp. 220-228
Allium ampeloprasum, Allium porrum, amino acids, breeding, breeding lines, cultivars, fructose, glucose, human health, industry, juices, kaempferol, kestose, leeks, metabolites, nuclear magnetic resonance spectroscopy, organic acids and salts, phytochemicals, quality control, quercetin, sucrose
INTRODUCTION: Leek (Allium ampeloprasum var. porrum) is consumed as a vegetable throughout the world. However, little is known about the metabolites of leek cultivars, especially those with potentially important beneficial properties for human health. OBJECTIVE: We provide new information for the overall metabolite composition of several leek cultivars grown in Europe by using HPLC–MS and ¹H NMR. METHODS: The use of a novel CTLS/NMR (constrained total‐line‐shape nuclear magnetic resonance) approach was found to be capable of reliable quantification, even with overlapping metabolite signals in the ¹H NMR of plant metabolites. Additionally, a new application for leek flavonoids was optimised for HPLC–MS. RESULTS: The total concentration of carbohydrates (glucose, fructose, kestose/nystose and sucrose) and nine amino acids varied by fourfold in leek juice from different cultivars, while the total concentrations of four organic acids were similar in all cultivars. All the quantified flavonols were kaempferol derivatives or quercetin derivatives and threefold differences in flavonol concentrations were detected between cultivars. CONCLUSION: In this study, various phytochemical profiles were determined for several leek cultivars by ¹H NMR spectroscopy with CTLS combined with HPLC–MS. The wide variation in bioactive compounds among commercial leek cultivars offers promising opportunities for breeders to raise the levels of important biochemical compounds in leek breeding lines, and also provides some objective measure for quality assurance for the leek industry.