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Robert Verpoorte

Publications and source records attributed to Robert Verpoorte.

At least 19 recordsLinked to original sources
PubMed2006

Vitamin K1 accumulation in tobacco plants overexpressing bacterial genes involved in the biosynthesis of salicylic acid.

Phylloquinone (Vitamin K(1)) is an essential component of the photosynthetic electron transfer. As isochorismate is required for the biosynthesis of Vitamin K(1), isochorismate synthase (ICS) activity is expected to be present in all green plants. In bacteria salicylic acid (SA) is synthesized via a two step pathway involving ICS and isochorismate pyruvate lyase (IPL). The effect of the introduction in tobacco plants of the bacterial ICS and IPL genes on the endogenous isochorismate pathway was investigated. Transgenic tobacco plants in which IPL was targeted to the chloroplast suffered severe growth retardation and had low Vitamin K(1) content. Probably because isochorismate was channeled towards SA production, the plants were no longer able to produce normal levels of Vitamin K(1). Transgenic tobacco plants in which the bacterial ICS was present in the chloroplast showed higher Vitamin K(1) contents than wild type plants.

Bacterial Proteins↗
PubMed2006

Metabolomic differentiation of Brassica rapa following herbivory by different insect instars using two-dimensional nuclear magnetic resonance spectroscopy.

The metabolic alterations of Brassica rapa (L.) leaves attacked by larvae of the specialist Plutella xylostella L. (Lepidoptera: Yponomeutidae) and the generalist Spodoptera exigua Hubner (Lepidoptera: Noctuidae) were investigated with nuclear magnetic resonance (NMR) spectroscopy, followed by a multivariate data analysis. The principal component analysis (PCA) of (1)H NMR spectra showed that metabolic changes in B. rapa leaves induced by the 2nd and the 4th instars were different from each other. However, the congestion of the one-dimensional (1)H NMR spectrum made it difficult to identify discriminating metabolites. To overcome the spectral complexity, several two-dimensional NMR techniques were applied. Of those evaluated, J-resolved spectroscopy, which affords an additional coupling constant, provided a wide range of structure information on differentiating the metabolites. Based on the J-resolved spectra combined with PCA, the major signals contributing to the discrimination were alanine, threonine, glucose, sucrose, feruloyl malate, sinapoyl malate, and gluconapin.

Animals↗
PubMed2006

Metabolomic analysis of methyl jasmonate treated Brassica rapa leaves by 2-dimensional NMR spectroscopy.

The metabolomic analysis of Brassica rapa leaves treated with methyl jasmonate was performed using 2-dimensional J-resolved NMR spectroscopy combined with multivariate data analysis. The principal component analysis of the J-resolved NMR spectra showed discrimination between control and methyl jasmonate treated plants by principal components 1 and 2. While the level of glucose, sucrose and amino acids showed a decrease after methyl jasmonate treatment, hydroxycinnamates and glucosinolate were highly increased. Methyl jasmonate treatment resulted in a long-term accumulation of indole glucosinolate and indole-3-acetic acid, lasting up to 14 days after treatment. Malate conjugated hydroxycinnamates also exhibited an increase until 14 days after methyl jasmonate treatment, these compounds might play an important role in plant defence responses mediated by methyl jasmonate.

Acetates↗
PubMed2006

NMR metabolomics to revisit the tobacco mosaic virus infection in Nicotiana tabacum leaves.

Tobacco mosaic virus (TMV) infection of tobacco is a well-known and extensively studied model system for which a number of genes and proteins involved in the systemic acquired resistance (SAR) have been characterized. Little is known about the metabolic changes connected with the infection and SAR. Here we describe the use of NMR spectroscopy in combination with multivariate data analysis to study the metabolic changes. Particularly 2-D NMR methods, such as 2-D J-resolved spectra and their projected spectra, are shown to be powerful tools in the metabolomic studies. The macroscopic view of the metabolomes obtained by NMR spectroscopy of crude extracts enabled the identification of a series of totally different metabolites that seem connected with resistance, such as the clearly increased 5-caffeoylquinic acid, alpha-linolenic acid analogues, and sesqui- and diterpenoids in the infected plant parts.

Caffeic Acids↗
PubMed2006

Application of two-dimensional nuclear magnetic resonance spectroscopy to quality control of ginseng commercial products.

Ginseng has been used as a powder or a crude extract of the plant roots. The quality control of commercial ginseng preparations is difficult due to the diverse compounds present. Most previous quality control methods using TLC or HPLC-UV (or -MS) cannot be expected to cover a wide range of compounds in the commercial ginseng preparations. In this study, the metabolic fingerprinting of ginseng preparations was performed by (1)H-NMR spectroscopy. Although (1)H-NMR spectroscopy could provide information about the total profile of the compounds present, low resolution and overlapping signals make it difficult for further identification of each compound. For overcoming the problem two-dimensional J-resolved NMR spectra and multivariate data analysis techniques was applied for the analysis. Principal component analysis (PCA) of projected J-resolved NMR spectra shows a clear discrimination among those samples by principal component 1 and principal component 3. The loading plot of PC values obtained from all NMR signals indicates that alanine, arginine, choline, fumaric acid, inositol, sucrose as well as ginsenosides are important metabolites to differentiate the preparations from each other. This method allows an efficient discrimination of a ginseng preparation in less than 15 minutes without any pre-purification steps.

Humans↗
PubMed2005

Liquid chromatography-diode array detection-electrospray ionisation mass spectrometry/nuclear magnetic resonance analyses of the anti-hyperglycemic flavonoid extract of Genista tenera. Structure elucidation of a flavonoid-C-glycoside.

The anti-hyperglycemic flavonoid extract obtained from Genista tenera was first studied by liquid chromatography (LC)-diode array detection (DAD) which showed the presence of two major compounds. One of them was identified as genistein-7-O-glucoside. Luteolin-7-O-glucoside was detected as a minor constituent, while luteolin-7,3'-di-O-glucoside and rutin were found in trace amounts. LC-DAD-ESI-MS and NMR were used to confirm the structure of these compounds and allowed the elucidation of the structure of the unknown major compound, which is the flavonoid 5,7,4'-trihydroxyisoflavone-8-C-glucoside.

Carbohydrate Conformation↗
PubMed2005

Classification of Ilex species based on metabolomic fingerprinting using nuclear magnetic resonance and multivariate data analysis.

The metabolomic analysis of 11 Ilex species, I. argentina, I. brasiliensis, I. brevicuspis, I. dumosavar. dumosa, I. dumosa var. guaranina, I. integerrima, I. microdonta, I. paraguariensis var. paraguariensis, I. pseudobuxus, I. taubertiana, and I. theezans, was carried out by NMR spectroscopy and multivariate data analysis. The analysis using principal component analysis and classification of the (1)H NMR spectra showed a clear discrimination of those samples based on the metabolites present in the organic and aqueous fractions. The major metabolites that contribute to the discrimination are arbutin, caffeine, phenylpropanoids, and theobromine. Among those metabolites, arbutin, which has not been reported yet as a constituent of Ilex species, was found to be a biomarker for I. argentina,I. brasiliensis, I. brevicuspis, I. integerrima, I. microdonta, I. pseudobuxus, I. taubertiana, and I. theezans. This reliable method based on the determination of a large number of metabolites makes the chemotaxonomical analysis of Ilex species possible.

Analysis of Variance↗
PubMed2005

Proteome analysis of the medicinal plant Catharanthus roseus.

A proteomic approach is undertaken aiming at the identification of novel proteins involved in the alkaloid biosynthesis of Catharanthus roseus. The C. roseus cell suspension culture A11 accumulates the terpenoid indole alkaloids strictosidine, ajmalicine and vindolinine. Cells were grown for 21 days, and alkaloid accumulation was monitored during this period. After a rapid increase between day 3 and day 6, the alkaloid content reached a maximum on day 16. Systematic analysis of the proteome was performed by two-dimensional polyacrylamide gel electrophoresis. After day 3, the proteome started to change with an increasing number of protein spots. On day 13, the proteome changed back to roughly the same as at the start of the growth cycle. 88 protein spots were selected for identification by mass spectrometry (MALDI-MS/MS). Of these, 58 were identified, including two isoforms of strictosidine synthase (EC 4.3.3.2), which catalyzes the formation of strictosidine in the alkaloid biosynthesis; tryptophan synthase (EC 4.1.1.28), which is needed for the supply of the alkaloid precursor tryptamine; 12-oxophytodienoate reductase, which is indirectly involved in the alkaloid biosynthesis as it catalyzes the last step in the biosynthesis of the regulator jasmonic acid. Unique sequences were found, which may also relate to unidentified biosynthetic proteins.

Alkaloids↗
PubMed2005

Elicitor signal transduction leading to production of plant secondary metabolites.

Plant secondary metabolites are unique sources for pharmaceuticals, food additives, flavors, and other industrial materials. Accumulation of such metabolites often occurs in plants subjected to stresses including various elicitors or signal molecules. Understanding signal transduction paths underlying elicitor-induced production of secondary metabolites is important for optimizing their commercial production. This paper summarizes progress made on several aspects of elicitor signal transduction leading to production of plant secondary metabolites, including: elicitor signal perception by various receptors of plants; avirulence determinants and corresponding plant R proteins; heterotrimeric and small GTP binding proteins; ion fluxes, especially Ca2+ influx, and Ca2+ signaling; medium alkalinization and cytoplasmic acidification; oxidative burst and reactive oxygen species; inositol trisphosphates and cyclic nucleotides (cAMP and cGMP); salicylic acid and nitric oxide; jasmonate, ethylene, and abscisic acid signaling; oxylipin signals such as allene oxide synthase-dependent jasmonate and hydroperoxide lyase-dependent C12 and C6 volatiles; as well as other lipid messengers such as lysophosphatidylcholine, phosphatidic acid, and diacylglycerol. All these signal components are employed directly or indirectly by elicitors for induction of plant secondary metabolite accumulation. Cross-talk between different signaling pathways is very common in plant defense response, thus the cross-talk amongst these signaling pathways, such as elicitor and jasmonate, jasmonate and ethylene, and each of these with reactive oxygen species, is discussed separately. This review also highlights the integration of multiple signaling pathways into or by transcription factors, as well as the linkage of the above signal components in elicitor signaling network through protein phosphorylation and dephosphorylation. Some perspectives on elicitor signal transduction and plant secondary metabolism at the transcriptome and metabolome levels are also presented.

Gene Expression Regulation, Plant↗
PubMed2005

Characterization of a polyclonal antiserum against the monoterpene monooxygenase, geraniol 10-hydroxylase from Catharanthus roseus.

Geraniol 10-hydroxylase (G10H) is a P450 containing enzyme which is the first committed step in the biosynthesis of monoterpene indole alkaloids (MIAs), including the Catharanthus roseus-anticancer drugs vinblastine and vincristine. It is thought that G10H has a regulatory role in MIA production. In the present paper, we report the characterization of a polyclonal serum raised against the purified G10H polypeptide. Anti-G10H IgG was able to inhibit the G10H activity and also recognized the G10H polypeptide from C. roseus and other plants producing MIAs. These results establish the usefulness of this antiserum as a biochemical tool for the study of G10H regulation.

Animals↗
PubMed2005

Comparing metabolomes: the chemical consequences of hybridization in plants.

Hybridization may lead to unique phytochemical expression in plant individuals. Hybrids may express novel combinations or extreme concentrations of secondary metabolites or, in some cases, produce metabolites novel to both parental species. Here we test whether there is evidence for extreme metabolite expression or novelty in F1 hybrids between Senecio aquaticus and Senecio jacobaea. Hybridization is thought to occur frequently within Senecio, and hybridization might facilitate secondary metabolite diversification within this genus. Parental species express different quantities of several classes of compounds known to be involved in antiherbivore defence, including pyrrolizidine alkaloids, chlorogenic acid, flavonoids and benzoquinoids. Hybrids demonstrate differential expression of some metabolites, producing lower concentrations of amino acids, and perhaps flavonoids, than either parental species. Despite evidence for quantitative hybrid novelty in this system, NMR profiling did not detect any novel compounds among the plant groups studied. Metabolomic profiling is a useful technique for identifying qualitative changes in major metabolites according to plant species and/or genotype, but is less useful for identifying small differences between plant groups, or differences in compounds expressed in low concentrations.

Hybridization, Genetic↗
PubMed2005

Metabolic fingerprinting of Ephedra species using 1H-NMR spectroscopy and principal component analysis.

The metabolomic analysis of Ephedra species was performed using 1H-NMR spectroscopy and multivariate data analysis. A broad range of metabolites could be detected by 1H-NMR spectroscopy without any chromatographic separation. The principal component analysis used to reduce the huge data set obtained from the 1H-NMR spectra of the plant extracts clearly discriminated three different Ephedra species. The major differences in Ephedra sinica, Ephedra intermedia and Ephedra distachya var. distachya were found to be due to benzoic acid analogues in the aqueous fraction and ephedrine-type alkaloids in the organic fraction. Based on this metabolomic recognition, one of nine commercial Ephedra materials evaluated was shown to be a mixture of Ephedra species. This method will be a useful tool for chemotaxonomic analysis and authentification of Ephedra species including quality control of plant materials.

Ephedra↗
PubMed2004

Metabolic discrimination of Catharanthus roseus leaves infected by phytoplasma using 1H-NMR spectroscopy and multivariate data analysis.

A comprehensive metabolomic profiling of Catharanthus roseus L. G. Don infected by 10 types of phytoplasmas was carried out using one-dimensional and two-dimensional NMR spectroscopy followed by principal component analysis (PCA), an unsupervised clustering method requiring no knowledge of the data set and used to reduce the dimensionality of multivariate data while preserving most of the variance within it. With a combination of these techniques, we were able to identify those metabolites that were present in different levels in phytoplasma-infected C. roseus leaves than in healthy ones. The infection by phytoplasma in C. roseus leaves causes an increase of metabolites related to the biosynthetic pathways of phenylpropanoids or terpenoid indole alkaloids: chlorogenic acid, loganic acid, secologanin, and vindoline. Furthermore, higher abundance of Glc, Glu, polyphenols, succinic acid, and Suc were detected in the phytoplasma-infected leaves. The PCA of the (1)H-NMR signals of healthy and phytoplasma-infected C. roseus leaves shows that these metabolites are major discriminating factors to characterize the phytoplasma-infected C. roseus leaves from healthy ones. Based on the NMR and PCA analysis, it might be suggested that the biosynthetic pathway of terpenoid indole alkaloids, together with that of phenylpropanoids, is stimulated by the infection of phytoplasma.

Catharanthus↗
PubMed2004

Development of a validated HPLC method for the determination of B-complex vitamins in pharmaceuticals and biological fluids after solid phase extraction.

An HPLC method was developed for the simultaneous determination of seven water-soluble vitamins, viz. thiamine, riboflavin, nicotinic acid, nicotinamide, pyridoxine, cyanocobalamin, and folic acid, in multivitamin pharmaceutical formulations and biological fluids (blood serum and urine). Separation was achieved at ambient temperature on a Phenomenex Luna C18 (150 x 4.6 mm) analytical column. Gradient elution was performed starting at a 99:1 A:B v/v composition, where A: 0.05 M CH3COONH4/CH3OH (99/1) and B: H2O/CH3OH (50/50), at a flow rate of 0.8 mL/min. After a 4-min isocratic elution the composition was changed to 100% of B in 18 min and elution continued isocratically for 8 min. Detection was performed with a photodiode array detector at 280 nm. Each vitamin was quantitatively determined at its maximum wavelength. Spectral comparison was used for peak identification in real samples. Detection limits were in the range of 1.6-3.4 ng, per 20-microL injection, while linearity held up to 25 ng/microL. Accuracy, intra-day repeatability (n = 6), and inter-day precision (n = 7) were found to be satisfactory. Theobromine (2 ng/microL) was used as internal standard. Sample preparation of biological fluids was performed by SPE on Supelclean LC-18 cartridges with methanol-water 85/15 v/v as eluent. Extraction recoveries from biological matrices ranged from 84.6% to 103.0%.

Chromatography, High Pressure Liquid↗
PubMed2004

Antioxidant lignan glucosides from Strychnos vanprukii.

From the stem of Strychnos vanprukii, two new lignan glucosides, vanprukoside (1) and strychnoside (2), were isolated together with the known lignan glucoside, (+)-lyoniresinol-3 alpha-O-beta-glucopyranoside (3). The structures of these compounds were elucidated on the basis of their spectroscopic data. All three compounds exhibited antioxidant activity.

Antioxidants↗
PubMed2004

Metabolic fingerprinting of wild type and transgenic tobacco plants by 1H NMR and multivariate analysis technique.

The metabolomic analysis of wild type and constitutive salicylic acid producing tobacco plants (CSA tobacco, Nicotiana tabacum 'Samsun' NN) plants overexpressing salicylate biosynthetic genes was carried out by 1H NMR spectrometry and multivariate analysis techniques. The principle component analysis (PCA) of the 1H NMR spectra showed a clear discrimination between those samples by PC1 and PC2. The discrimination of non-inoculated, TMV-virus inoculated, and systemic leaves or veins could also be obtained by PCA analysis. Major peaks in 1H NMR spectra contributing to the discrimination were assigned as those of chlorogenic acid, malic acid, and sugars. This method allows an efficient differentiation between wild type and transgenic plants without any pre-purification steps.

Chlorogenic Acid↗