Quantitative metabolite profiling of edible onion species by NMR and HPLC-MS.

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.

Metabolite profiling of leek (Allium porrum L) cultivars by (1) H NMR and HPLC-MS.

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 (1) H 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 (1) H 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 (1) H 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.

beta-Amyloid infusion results in delayed and age-dependent learning deficits without role of inflammation or beta-amyloid deposits.

beta-Amyloid (Abeta) polypeptide plays a critical role in the pathogenesis of Alzheimer's disease (AD), which is characterized by progressive decline of cognitive functions, formation of Abeta deposits and neurofibrillary tangles, and loss of neurons. Increased genetic production or direct intracerebral administration of Abeta in animal models results in Abeta deposition, gliosis, and impaired cognitive functions. Whether aging renders the brain prone to Abeta and whether inflammation is required for Abeta-induced learning deficits is unclear. We show that intraventricular infusion of Abeta1-42 results in learning deficits in 9-month-old but not 2.5-month-old mice. Deficits that become detectable 12 weeks after the infusion are associated with a slight reduction in Cu,Zn superoxide dismutase activity but do not correlate with Abeta deposition and are not associated with gliosis. In rats, Abeta infusion induced learning deficits that were detectable 6 months after the infusion. Approximately 20% of the Abeta immunoreactivity in rats was associated with astrocytes. NMR spectrum analysis of the animals cerebrospinal fluid revealed a strong reduction trend in several metabolites in Abeta-infused rats, including lactate and myo-inositol, supporting the idea of dysfunctional astrocytes. Even a subtle increase in brain Abeta1-42 concentration may disrupt normal metabolism of astrocytes, resulting in altered neuronal functions and age-related development of learning deficits independent of Abeta deposition and inflammation.