Separation of phenolic acids in soil and plant tissue extracts by co-electroosmotic capillary electrophoresis with direct UV detection

Physiological and transcriptomic analyses to reveal underlying phenolic acid action in consecutive monoculture problem of Polygonatum odoratum

BACKGROUND

The root rot of fragrant solomonseal (Polygonatum odoratum) has occurred frequently in the traditional P. odoratum cultivating areas in recent years, causing a heavy loss in yield and quality. The phenolic acids in soil, which are the exudates from the P. odoratum root, act as allelochemicals that contribute to the consecutive monoculture problem (CMP) of the medicinal plant. The aim of this study was to get a better understanding of P. odoratum CMP.

RESULTS

The phenolic acid contents, the nutrient chemical contents, and the enzyme activities related to the soil nutrient metabolism in the first cropping (FC) soil and continuous cropping (CC) soil were determined, and the differentially expressed genes (DEGs) related to the regulation of the phenolic acids in roots were analyzed. The results showed that five low-molecule-weight phenolic acids were detected both in the CC soil and FC soil, but the phenolic acid contents in the CC soil were significantly higher than those in the FC soil except vanillic acid. The contents of the available nitrogen, available phosphorus, and available potassium in the CC soil were significantly decreased, and the activities of urease and sucrase in the CC soil were significantly decreased. The genomic analysis showed that the phenolic acid anabolism in P. odoratum in the CC soil was promoted. These results indicated that the phenolic acids were accumulated in the CC soil, the nutrient condition in the CC soil deteriorated, and the nitrogen metabolism and sugar catabolism of the CC soil were lowered. Meantime, the anabolism of phenolic acids was increased in the CC plant.

CONCLUSIONS

The CC system promoted the phenolic acid anabolism in P. odoratum and made phenolic acids accumulate in the soil.

Confirmation of vanadium complex formation using electrospray mass spectrometry and determination of vanadium speciation by sample stacking capillary electrophoresis

Capillary zone electrophoresis (CZE) with UV detection was used to determine vanadium species. Nitrilotriacetic acid (NTA), hydroxyethylethylenediaminetriacetic acid (HEDTA), ethylenediaminetetraacetic acid (EDTA), diethylenetriaminepentaacetic acid (DTPA), ethylene glycol-bis(2-aminoethylether)-tetraacetic acid (EGTA) and 2,6-pyridinedicarboxylic acid (PDCA) were investigated to determine whether these ligands formed stable anionic complexes with vanadium. Of all the ligands studied HEDTA was the most suitable ligand because it gave the largest UV response with reasonable migration time. Electrospray mass spectrometry (ES-MS) was used to confirm the formation of [VO(2)(HEDTA)](2-) and [VO(HEDTA)](1-) in solution. An electrolyte containing 25 mM phosphate, 0.25 mM tetradecyltrimethylammonium bromide (TTAB) at pH 5.5 was optimum for the separation of these anionic vanadium complexes. Sample stacking techniques, including large-volume sample stacking (LVSS) and field-amplified sample injection (FASI), were tested to improve the sensitivity. Best sensitivity was obtained using FASI, with detection limits of 0.001 microM, equivalent to 0.4 microg L(-1), for [VO(2)(HEDTA)](2-) and 0.01 microM, equivalent to 3.4 microg L(-1) for [VO(HEDTA)](1-). The utility of the method for the speciation of V(IV) and V(V) was demonstrated using ground water samples.

Capillary zone electrophoretic determination of phenolic compounds in chess (Bromus inermisL.) plant extracts

A simple CZE method for quantification of phenolic compounds (vanillin, cinnamic, sinapic, chlorogenic, syringic, ferulic, benzoic, p-coumaric, vanillic, p-hydroxybenzoic, rosmarinic, caffeic, gallic and protocatechuic acids) in less than 10 min using 20 mM sodium tetraborate (pH 9.2) with 5% v/v methanol as a BGE and with UV detection at 254 nm is described. The LODs (3 S/N) ranged between 0.02 and 0.12 microg/ mL. Repeatabilities (RSDs) were 0.66-1.8 and 1.56-4.23% for migration times and peak areas (n = 5), respectively. The method was applied to the determination of phenolic compounds in chess (Bromus inermis L.) after Soxhlet extraction and purification of the crude extracts with SPE procedures. The results compared well with those obtained by liquid chromatographic method. B. inermis was found as a suitable model plant containing a broad spectrum of phenolic compounds in easily detectable concentrations and as a potential source of antioxidants.

Determination of 3-methylhistidine and 1-methylhistidine in untreated urine samples by capillary electrophoresis

Capillary electrophoretic (CE) method was developed for the determination of urinary 3-methylhistidine (3MH) and 1-methylhistidine (1MH) indicating the extent of degradation of skeletal muscle proteins and thereby the state of human health. 3MH, 1MH and histidine can be separated in both acidic and alkaline media, where these amino acids form cation and anion, respectively. The effective mobility of all ionic forms was measured over a broad range of pH (1.67-11.80), which made it possible to evaluate the corresponding dissociation constants. 3MH and 1MH were determined together with creatinine in untreated urine samples with the limit of detection of 2.4 microM (0.4 mgL(-1)) and 3.0 microM (0.5 mgL(-1)), respectively. Determination was fast and took ca. 12 min including the column washing. Method was employed for an analysis of urine collected from healthy individuals, and from the patients hospitalized with obesity and diabetes mellitus II. This analysis has revealed differences between the healthy individuals and the patients pointing to a more extensive degradation of muscle proteins in the latter group.

On-column complexation capillary electrophoretic separation of Fe2+ and Fe3+ using 2,6-pyridinedicarboxylic acid coupled with large-volume sample stacking

On-column complexation of Fe2+ and Fe3+ with 2,6-pyridinedicarboxylic acid (2,6-PDCA) formed anionic complexes, which were then separated by capillary zone electrophoresis with direct UV detection at 214 nm. To achieve reasonable separation selectivity and on-column complexation, the conditions such as pH, the concentration of 2,6-PCDA and the EOF modifiers in the electrolyte were examined. The electrolyte contained 5.0 mM 2,6-PDCA, 0.25 mM tetradecyltrimethlammonium bromide (TTAB) and 5% (v/v) acetonitrile at pH 4.0 was optimised for on-column complexation and the separation of Fe[PCDA]2(2-) and Fe[PCDA]2(-). To enhance the detection sensitivity, large-volume sample stacking (LVSS) was used for the on-line preconcentration of Fe[PCDA]2(2-) and Fe[PCDA]2(-). Under the optimised conditions, satisfactory working ranges (0.5-50 microM), lower detection limits (less than 0.1 microM) and good repeatability of the peak areas (R.S.D.: 5.2-7.8%, n = 5) was achieved using LVSS (300 s). With LVSS, the detection sensitivity was enhanced more than 50-fold compared to conventional hydrodynamic injection. The proposed method was used successfully for the determination of Fe2+ and Fe3+ in water samples.

Capillary electrophoresis-based profiling and quantitation of total salicylic acid and related phenolics for analysis of early signaling in Arabidopsis disease resistance

A capillary electrophoresis-based method for quantitation of total salicylic acid levels in Arabidopsis leaves was developed. Direct comparison to previous high-performance liquid chromatography (HPLC)-based measurements showed similar levels of salicylic acid. Simultaneous quantitation of trans-cinnamic acid, benzoic acid, sinapic acid, and an internal recovery standard was achieved. A rapid, streamlined protocol with requirements for plant tissue reduced relative to those of HPLC-based protocols is presented. Complicated, multiparameter experiments were thus possible despite the labor-intensive nature of inoculating plants with bacterial pathogens. As an example of this sort of experiment, detailed time course studies of total salicylic acid accumulation by wild-type Arabidopsis and two lines with mutations affecting salicylic acid accumulation in response to either of two avirulent bacterial strains were performed. Accumulation in the first 12h was biphasic. The first phase was partially SID2 and NDR1 dependent with both bacterial strains. The second phase was largely independent of both genes with bacteria carrying avrB, but dependent upon both genes with bacteria carrying avrRpt2. Virulent bacteria did not elicit salicylic acid accumulation at these time points. Application of this method to various Arabidopsis pathosystems and the wealth of available disease resistance signaling mutants will refine knowledge of disease resistance and associated signal transduction.

Separation of arsenic species by capillary electrophoresis with sample-stacking techniques

A simple capillary zone electrophoresis procedure was developed for the separation of arsenic species (AsO(2)(2-), AsO(4)(2-), and dimethylarsinic acid, DMA). Both counter-electroosmotic and co-electroosmotic (EOF) modes were investigated for the separation of arsenic species with direct UV detection at 185 nm using 20 mmol L(-1) sodium phosphate as the electrolyte. The separation selectivity mainly depends on the separation modes and electrolyte pH. Inorganic anions (Cl(-), NO(2)(-), NO(3)(-) and SO(4)(2-)) presented in real samples did not interfere with arsenic speciation in either separation mode. To improve the detection limits, sample-stacking techniques, including large-volume sample stacking (LVSS) and field-amplified sample injection (FASI), were investigated for the preconcentration of As species in co-CZE mode. Less than 1 micromol L(-1) of detection limits for As species were achieved using FASI. The proposed method was demonstrated for the separation and detection of As species in water.

On-column complexation of metal ions using 2,6-pyridinedicarboxylic acid and separation of their anionic complexes by capillary electrophoresis with direct UV detection

On-column complexation of metal ions with 2,6-pyridinedicarboxylate (2,6-PDC) to form anionic complexes enabled their separation by capillary zone electrophoresis with direct UV detection at 214 nm. Nine metal ions, Cu2+, Zn2+, Ni2+, Cd2+ Mn2+, Pb2+, Fe3+, Al3+ and Ca2+, were determined in less than 7 min using 10 mM 2.6-PDC solution containing 0.75 mM tetradecyltrimethylammonium bromide at pH 4.0. Satisfactory working ranges (20-300 microM), detection limits (3-10 microM) and good repeatability of the peak areas (RSD 2.1-4.2%, n=5) were obtained using hydrodynamic injection (30 s). The proposed method was used successfully for the determination of Mn2+, Fe3+, Al3+ and Ca2+ in groundwaters.

Analysis of phenolic acids by micellar electrokinetic chromatography: application to Echinacea purpurea plant extracts

A micellar electrokinetic chromatographic (MEKC) method was developed for the separation of ten phenolic acids including cichoric acid and caftaric acids, specific marker phytochemicals of Echinacea purpurea. The MEKC method involved the use of 70 mM sodium deoxycholate (SDC) in 40 mM borate (pH 9.2) buffer and UV detection at 300 nm. The bile acid was used as biosurfactant able to provided a micellar system with different and more selective properties than sodium dodecyl sulfate. The effects of SDC and borate concentration and buffer pH on the analyte resolution were evaluated. The validated method was applied to the determination of cichoric acid and related compounds in E. purpurea root extracts, and in commercial E. purpurea based dried extracts and tablets.