Metabolic profile of lettuce leaves by high-field NMR spectra

Abstract

A detailed analysis of the proton high-field NMR spectra of aqueous and organic extracts of lettuce leaves is reported for the first time. A combination of COSY, TOCSY, 1 H-13 C HSQC, 1 H-13 C HMBC bidimensional sequences and DOSY was used to assign each spin system and to separate the components of the complex patterns. A large number of water-soluble metabolites belonging to different classes such as carbohydrates, polyols, organic acids and amino acids were fully assigned. Moreover, the complex spectra of metabolites extracted in organic solvents belonging to sterols, fatty acids, diacylglycerophospholipids, galactosyldiacylglycerols, sulpholipids, pheophytins, carotenoids and hydrocarbons were also assigned.

NMR-Metabolic Methodology in the Study of GM Foods

“…Simple methods for extraction of water-soluble and lipo-soluble metabolites need to be applied [6,18]. The use of deuterated water for a direct extraction of metabolites from lyophilized tissues is a simple method to avoid any intermediate steps (for example, extraction by H 2 O followed by freeze-drying).…”

“…Water-soluble extracts were prepared as reported previously [6]: 1 mL of a D 2 O phosphate buffer, having 400 mM salt concentration, pD value of 6.5 and containing 0.3 mM of 3-(trimethylsilyl)propionic-2,2,3,3-d 4 acid sodium salt (TSPA) -0.05 mM EDTA, was mixed with 21.0 ± 0.2 mg of powdered vegetable tissues. The mixture was centrifuged at 10,000 rpm (5,600 g) for 7 min and the supernatant obtained was filtered and transferred into a standard 5 mm NMR tube.…”

“…To avoid possible saturation effects, the experiment was carried out by using a 45° flip angle pulse of 8.0 μs. 2D NMR experiments, namely 1 H-1 H TOCSY and 1 H-13 C HSQC, were performed using the same experimental conditions as previously reported [6].…”

“…Moreover, the system-wide metabolic analysis is becoming a useful tool for functional genomics [2]. NMR spectroscopy as a high-throughput analytical method is a powerful tool to study the metabolic profiles of foods of either animal or crop origin [3][4][5][6][7]. NMR-based identification and quantification of metabolites requires minimal preparation and handling, and no derivatization.…”

Use of NMR for metabolic profiling in plant systems

“…Substantial tables of assignments have been published for a number of samples of plant origin including apple, 17) mango, 9) orange, 10) tomato (fruit 12,18) and root 15) ), potato, 8) strawberry, 15) Arabidopsis (leaf 7) ) and lettuce (leaf 19) ). Most of these assignments were for aqueous samples or polar extracts and many compounds are common to all samples (e.g.…”