ABSTRACT
Quantitative metabolomics (qMetabolomics) is a powerful tool for understanding the intricate metabolic processes involved in plant abiotic stress responses. qMetabolomics is hindered by the limited coverage and high cost of isotopically labeled standards. In this study, we first selected 271 metabolites which might play important roles in abiotic stress responses as the targets and established a comprehensive LC-MS/MS based qMetabolomic method. We then developed a novel metabolic labeling method using E. coli-Saccharomyces cerevisiae two-step cultivation for the production of uniformly (13)C-labeled metabolites as internal standards. Finally, we applied the developed qMetabolomic method to investigate the influence of Pb stress on maize root metabolism. The absolute concentration of 226 metabolites in maize roots was accurately quantified in a single run within 30 min. Our study also revealed that glycolysis, purine, pyrimidine, and phospholipids were the main metabolic pathways in maize roots involved in Pb stress response. To our knowledge, this is the most comprehensive qMetabolomic method for plant metabolomics thus far. We developed a simple and inexpensive metabolic labeling method which dramatically expanded the availability of uniformly (13)C labeled metabolites. Our findings also provided new insights of maize metabolic responses to Pb stress.
Subject(s)
Metabolome , Plant Roots/metabolism , Zea mays/metabolism , Lead/pharmacology , Metabolomics , Plant Roots/drug effects , Stress, Physiological , Tandem Mass Spectrometry , Zea mays/drug effectsABSTRACT
As part of an evaluation of focused microwave-assisted extraction (FMAE) using an open-vessel system, the effects of matrix, moisture content, ageing, and solvent have been studied on the extraction efficiency of polycyclic aromatic hydrocarbons (PAHs) from spiked soils. PAHs were spiked onto three different uncontaminated air dried and originally wet soil matrices with 1- and 20-day ageing periods. Solvents used were hexane-acetone (1:1), cyclohexane-acetone (1:1) and dichloromethane. FMAE only required a small amount of solvent (20 ml) and short extraction time (10 min) in the open cell under 90 W of microwave power. The results revealed that the extraction efficiency strongly depends on the nature of soil matrix; moisture content may enhance the recoveries of PAHs for many cases; and, the influence of the type of solvent is not significant. A comparison between microwave extraction and 16-h Soxhlet extraction has been made on spiked soils. It evidenced that the microwave method under ambient pressure is a suitable alternative to Soxhlet method for the analysis of PAHs in soils. For the evaluation of the developed FMAE method, three reference materials were used. The PAHs recovered from three reference materials were in a good agreement with reference values.
Subject(s)
Chemistry Techniques, Analytical/methods , Polycyclic Aromatic Hydrocarbons/isolation & purification , Chemistry Techniques, Analytical/instrumentation , Microwaves , Reference Standards , Reproducibility of Results , Soil/analysis , Soil Pollutants/isolation & purification , Solvents/chemistry , Time FactorsABSTRACT
A total synthesis of (+/-)-sarracenin (1) is described. The key steps include (1) regioselective ring expansion of 7 to bicyclo[3.2.1]ketone6 and (2) ring opening of tricyclic ketone 5 to ester 4.
