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Results for “Targeted metabolomics”

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PubMed2003

Target validation in hypoxia-induced vascular remodeling using transcriptome/metabolome analysis.

The present study describes combined transcriptome and metabolome analysis for therapeutic target validation in hypoxia-induced vascular remodeling. Exposure to hypoxic conditions resulted in the upregulation of S100C mRNA and increased taurine (2-aminoethanesulfonic acid) content in the rat lung, as demonstrated by differential display and amino-acid content analysis. Hypoxia resulted in transcriptional activation of the S100C promoter through hypoxia-inducible factor-1 (HIF-1). Taurine suppressed HIF-1-mediated increases in S100C transcription. Moreover, oral taurine administration attenuated vascular remodeling in hypoxic rat lung, whereas depletion of endogenous taurine by administration of beta-alanine resulted in increased vascular remodeling. Inhibition of HIF transcription by taurine may be of therapeutic benefit in preventing hypoxia-induced vascular remodeling. In conclusion, we used transcriptome and metabolome analysis to identify a therapeutic low-molecular-weight ligand that plays a critical role in hypoxia-induced vascular remodeling. These techniques provided an excellent strategy for screening and validation of targets.

Animals↗

PubMed2004

Structural genomics and the metabolome: combining computational and NMR methods to identify target ligands.

One of the goals of structural genomics is to use three-dimensional structures to gain insights into the function of poorly understood or hypothetical proteins. Approximate functions are often apparent from the protein fold, but more precise biochemical functions are difficult to obtain from the structure alone. Analysis of the structure using a variety of informatics tools can lead to the identification of possible binding sites for small molecules. This knowledge can be used in combination with molecular docking and nuclear magnetic resonance screening methods to identify candidate target ligands for proteins of previously unknown function.

Binding Sites↗

PubMed2026

Genomic exploration and in silico prioritization of putative COX-2-targeting metabolites from Streptomyces sp. VITGV156 (MCC 4965).

INTRODUCTION: Streptomyces species represent an important source of bioactive natural products, yet systematic genome-guided prioritization of metabolites targeting cyclooxygenase-2 (COX-2/PTGS2) remains limited. This study aimed to investigate the biosynthetic potential of Streptomyces sp. VITGV156 (MCC 4965) using an integrated genome mining and computational drug discovery pipeline. METHODS: Whole-genome sequencing, functional annotation, antiSMASH v7.0.1-based biosynthetic gene cluster (BGC) prediction, LC-MS/MS metabolomic profiling, SwissADME analysis, target prediction, disease association mapping, molecular docking against PTGS2 (PDB: 5IKR), and PASS bioactivity prediction were performed to prioritize putative bioactive metabolites. RESULTS: Genome analysis identified 29 predicted biosynthetic gene clusters, including clusters associated with geosmin, ectoine, albaflavenone, hopene, coelichelin, and SapB, together with several cryptic clusters exhibiting low similarity to known pathways. LC-MS/MS metabolomic profiling provided experimental support for active secondary metabolite production under the cultivation conditions employed. Computational prioritization identified PTGS2 (COX-2) as a biologically relevant target. Molecular docking demonstrated favorable binding affinities and interaction profiles for several predicted metabolites within the PTGS2 catalytic pocket. PASS analysis further suggested potential anticancer-related biological activities that require experimental validation. DISCUSSION: These findings demonstrate the utility of integrating genome mining, metabolomic profiling, and computational drug discovery for prioritizing natural-product candidates. Streptomyces sp. VITGV156 (MCC 4965) represents a promising source of biosynthetic diversity and provides a genome-guided framework for identifying putative COX-2-targeting natural products for future experimental validation rather than confirming metabolite production or biological activity.

COX-2 (PTGS2)↗

PubMed2026

Comprehensive analysis of metabolomics and transcriptomics of radiation-induced rectal injury.

Radiation-induced rectal injury (RRI) significantly affects the quality of life in patients with locally advanced rectal cancer (LARC) undergoing neoadjuvant chemoradiotherapy (NCRT). Non-targeted liquid chromatography-mass spectrometry metabolomics analysis and transcriptomic analysis were conducted to explore RRI characteristics. Hematoxylin-eosin and Masson staining confirmed radiation-induced injury in rectal tissue within the radiotherapy target region. Orthogonal partial least squares discriminant analysis identified 823 differentially expressed metabolites (DEMs). Transcriptomic analysis revealed 400 differentially expressed genes (DEGs). Enrichment analysis revealed that DEMs and DEGs were primarily involved in metabolic, immune, and signal transduction pathways. Integrated analysis demonstrated significant enrichment of DEMs and DEGs in the arachidonic acid metabolism pathway. Pearson's correlation and canonical correlation analyses were used to assess the association between DEMs and DEGs within this pathway. In conclusion, this study identified key biological regulatory pathways involved in RRI through a multi-omics approach, offering potential targets for its diagnosis and treatment.

Humans↗

PubMed2006

Functional characterization of the flagellar glycosylation locus in Campylobacter jejuni 81-176 using a focused metabolomics approach.

Bacterial genome sequencing has provided a wealth of genetic data. However, the definitive functional characterization of hypothetical open reading frames and novel biosynthetic genes remains challenging. This is particularly true for genes involved in protein glycosylation because the isolation of their glycan moieties is often problematic. We have developed a focused metabolomics approach to define the function of flagellin glycosylation genes in Campylobacter jejuni 81-176. A capillary electrophoresis-electrospray mass spectrometry and precursor ion scanning method was used to examine cell lysates of C. jejuni 81-176 for sugar nucleotides. Novel nucleotide-activated intermediates of the pseudaminic acid (Pse5NAc7NAc) pathway and its acetamidino derivative (PseAm) were found to accumulate within select isogenic mutants, and use of a hydrophilic interaction liquid chromatography-mass spectrometry method permitted large scale purifications of the intermediates. NMR with cryo probe (cold probe) technology was utilized to complete the structural characterization of microgram quantities of CMP-5-acetamido-7-acetamidino-3,5,7,9-tetradeoxy-L-glycero-alpha-L-manno-nonulosonic acid (CMP-Pse5NAc7Am), which is the first report of Pse modified at C7 with an acetamidino group in Campylobacter, and UDP-2,4-diacetamido-2,4,6-trideoxy-alpha-D-glucopyranose, which is a bacillosamine derivative found in the N-linked proteinglycan. Using this focused metabolomics approach, pseB, pseC, pseF, pseI, and for the first time pseA, pseG, and pseH were found to be directly involved in either the biosynthesis of CMP-Pse5NAc7NAc or CMP-Pse5NAc7Am. In contrast, it was shown that pseD, pseE, Cj1314c, Cj1315c, Cjb1301, Cj1334, Cj1341c, and Cj1342c have no role in the CMP-Pse5NAc7NAc or CMP-Pse5NAc7Am pathways. These results demonstrate the usefulness of this approach for targeting compounds within the bacterial metabolome to assign function to genes, identify metabolic intermediates, and elucidate novel biosynthetic pathways.

Campylobacter jejuni↗

PubMed2005

Focused metabolomic profiling in the drug development process: advances from lipid profiling.

The highly parallel analytical technologies comprising 'omics promised to dramatically improve drug development efficiency by increasing knowledge and improving decision-making capabilities. On this point, the 'omics have largely been a disappointment. The major reason genomics, transcriptomics and proteomics fail to improve decision making capabilities is that they produce so many false positive results that it is difficult to be sure that findings are valid. Metabolomics is not immune to this problem but, when practiced effectively, the technology can reliably produce knowledge to aid in decision making. In particular, focused metabolomics platforms - those that restrict their target analytes to those measured well by the technology - can produce data with properties that maximize sensitivity and minimize the false discovery problem. The most developed focused metabolomics area is lipid profiling.

Animals↗

PubMed2005

Development of an HPLC-fluorescence determination method for carboxylic acids related to the tricarboxylic acid cycle as a metabolome tool.

We report the simultaneous determination of the carboxylic acids related to the tricarboxylic acid (TCA) cycle, which plays an important role in producing adenosine triphosphate (ATP) and generating energy in mitochondria. Seven carboxylic acids from the TCA cycle, and pyruvic acid and 2-methylsuccinic acid, as an internal standard, were derivatized with a fluorescent reagent for carboxyl groups, 4-N,N-dimethylaminosulfonyl-7-piperazino-2,1,3-benzoxadiazole (DBD-PZ), in the presence of 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide and 4-N,N-dimethyaminopyridine as the coupling reagents, at 60 degrees C for 120 min. Subsequently, the excess DBD-PZ was removed efficiently using a cation-exchange cartridge, SDB-RPS (Empore). These fluorescent derivatives were separated well from each other on an octadecyl silica column (TSKgel ODS-80Ts, 250 x 4.6 mm, i.d.) with an eluent of acetonitrile-water containing 1% formic acid at a flow rate of 0.8 mL/min, and were detected fluorometrically at 560 nm, with excitation at 450 nm. The validation data were satisfactory in the range of 2.5-100 microm citric acid, isocitric acid, 2-oxoglutaric acid, succinic acid and fumaric acid. The detection limit (S/N = 3) for citric acid was 2 fmol on the column. The structures of these derivatives were confirmed by high-performance liquid chromatography-mass spectrometry, which proved that their carboxylic groups were completely labeled with DBD-PZ, except for oxaloacetic acid. This HPLC method was successfully applied to the analysis of TCA cycle metabolites in rat urine. The method will also be useful for metabolome research, such as for target analyses of metabolites with carboxyl groups, not only in urine but also in cells and organs.

Animals↗

PubMed2006

Instrument dependence of electrospray ionization and tandem mass spectrometric fragmentation of the gingerols.

The gingerols, including [6]-, [8]-, and [10]-gingerols, a series of chemical homologs differentiated by the length of their unbranched alkyl chains, have been identified as major active components in fresh ginger rhizome. The purpose of this study was to investigate the utility of ion trap liquid chromatography/tandem mass spectrometry (LC/MS/MS) as an online tool to identify and quantify these compounds in raw or processed ginger rhizome samples. Negative mode electrospray ionization (ESI) was used in MS, MS/MS and MS(n) experiments in quadrupole ion trap instruments from two different manufacturers and in high-resolution and accurate mass MS and MS/MS experiments in a Fourier transform ion cyclotron resonance mass spectrometer to elucidate the ionization and fragmentation mechanisms of these compounds in these instruments. Positive mode ESI, which generated many more fragment ions in full scan MS even under gentle ionization conditions, was also used in LC/MS and MS/MS experiments and in direct infusion MS and MS/MS experiments. Consistent and predictable ionization and fragmentation behaviors were observed for all gingerols when analyzed in the same instrument. Instruments from different manufacturers, however, had different ionization mechanisms. The major difference between instruments was their ability to form covalent dimer adducts of the gingerols. Subsequent fragmentation patterns of the precursor ions were essentially identical. These results clearly demonstrate that LC/MS instruments produce data that cannot necessarily be replicated in other laboratories, especially if those laboratories do not have the same instrument model from the same manufacturer. This presents major problems for metabolite target analysis, metabolic profiling and metabolomics investigations, which would benefit from LC/MS mass spectrum libraries as they do from GC/MS mass spectrum libraries, because such libraries may not be valid across platforms.

Catechols↗

PubMed2005

How molecular profiling could revolutionize drug discovery.

Information from genomic, proteomic and metabolomic measurements has already benefited target discovery and validation, assessment of efficacy and toxicity of compounds, identification of disease subgroups and the prediction of responses of individual patients. Greater benefits can be expected from the application of these technologies on a significantly larger scale; by simultaneously collecting diverse measurements from the same subjects or cell cultures; by exploiting the steadily improving quantitative accuracy of the technologies; and by interpreting the emerging data in the context of underlying biological models of increasing sophistication. The benefits of applying molecular profiling to drug discovery and development will include much lower failure rates at all stages of the drug development pipeline, faster progression from discovery through to clinical trials and more successful therapies for patient subgroups. Upheavals in existing organizational structures in the current 'conveyor belt' models of drug discovery might be required to take full advantage of these methods.

Animals↗

PubMed2026

Identifying potential therapeutic targets for high myopia via a case-control study and Mendelian randomisation analyses of the human blood metabolome.

BACKGROUND: High myopia increases the risk of pathological ocular changes that may lead to irreversible vision loss. Therefore, the identification of potential biomarkers and therapeutic targets for high myopia is essential for early intervention and prevention. METHODS: Summary statistics for 122 blood metabolites were obtained from three genome-wide association studies (GWASs), whereas data on high myopia were derived from a large GWAS conducted with 50,372 participants from the UK Biobank. Mendelian randomisation (MR) analyses were conducted to assess the causal relationships between blood metabolites and high myopia. A real-world case-control study was conducted to validate the causal associations identified in the MR analyses. RESULTS: The systematic MR analysis identified 5 blood metabolites as both biomarkers and potential drug targets for high myopia, including glutamine (odds ratio [OR]: 0.98, 95% confidence interval [CI]: 0.97-1.00), tyrosine (OR: 0.98; 95% CI: 0.97-0.99), degree of unsaturation (OR: 0.98, 95% CI: 0.98-0.99), docosahexaenoic acid (DHA) (OR: 0.99; 95% CI: 0.98-1.00) and isobutyrylcarnitine (OR: 1.09, 95% CI: 1.05-1.13). The case-control study indicated that the levels of glutamine (OR = 0.76, 95% CI: 0.58-0.98) and tyrosine (OR = 0.72, 95% CI: 0.55-0.94) were significantly associated with a decreased risk of high myopia. CONCLUSIONS: Systematic MR analysis suggested that glutamine, tyrosine, the degree of unsaturation, DHA, and isobutyrylcarnitine may represent promising drug targets for high myopia prevention. Further investigations are needed to validate the therapeutic efficacy and elucidate the underlying mechanisms involved.

Humans↗

PubMed2002

Metabolomics of plant saponins: bioprospecting triterpene glycoside diversity with respect to mammalian cell targets.

One of the goals of cancer chemotherapy and prevention is the discovery of compounds that are relatively selective to tumor cells and, therefore, have reduced effects on normal cell growth. In previously published studies, it was shown that certain triterpene saponins (called avicins) from a desert tree, Acacia victoriae, are selectively toxic to tumor cells at very low doses (IC(50): 0.2 microg/mL for Jurkat cells). To extend this research to human clinical studies, we needed to find a reliable supply of avicins and have developed a transformed "hairy root" culture as a means of biomass production. Protocols were optimized for A. victoriae micropropagation; after a boiling water treatment, A. victoriae seeds were maintained under in vitro conditions on defined media. Embryo-axis explants from shoot tips were removed and infected with Agrobacterium rhizogenes Conn (R 1000) for hairy root induction. Plasmid integration was confirmed by PCR analysis with a primer set for a segment of the rol B gene. Culture conditions have been optimized for root biomass production, and various inducers have been investigated for enhancement of avicin production. Hairy root cultures were compared with intact pod tissue from field-grown sources for avicin content following partial purification of triterpene glycosides and HPLC separation of the secondary metabolites. From bioassays of the collected HPLC fractions, we have identified putative triterpene "metabolic clusters" with enhanced activity against tumor cells. This now provides a system for both production of clinical trial lots of active samples, but also a means to correlate structure of individual triterpene glycosides with specific cellular target activity in mammalian cells.

Acacia↗

PubMed2004

Additional paper: computational resources for metabolomics.

Metabolomics, a comprehensive extension of traditional targeted metabolite analysis, has recently attracted much attention as the biological jigsaw puzzle's missing piece that can complement transcriptome and proteome analysis. This tutorial survey introduces practical web resources with special emphasis on the computational aspects involved in processing and navigating metabolome data. The introduced materials are also accessible from the author's web directory (Atomic Reconstruction of Metabolism or ARM).

Algorithms↗

PubMed2026

Blood Metabolomic Signatures of 1-Hour Glucose Predict Cardiometabolic Risk.

BACKGROUND: Elevated 1-hour glucose levels during an oral glucose tolerance test strongly predict type 2 diabetes (T2D) and cardiovascular disease. We investigated whether the fasting blood metabolome predicting 1-hour glucose could be a target for improving β-cell function, long-term glycemic trajectories, and reducing the risks of T2D and coronary heart disease. We also investigated whether plasma microRNAs derived from key metabolic organs regulate changes in a metabolomic risk score (MRS) for predicting 1-hour glucose. METHODS: Untargeted blood metabolomics and a frequently sampled 75-g oral glucose tolerance test were performed in participants from the OmniCarb trial (n=162). In an independent weight-loss dietary intervention trial (POUNDS Lost [Preventing Overweight Using Novel Dietary Strategies]), temporal changes in MRS and plasma microRNAs measured by genome-wide sequencing were analyzed. In addition, associations of MRS at baseline and its 10-year changes with long-term risk of incident T2D and coronary heart disease were prospectively investigated in the NHS (Nurses' Health Study). RESULTS: We created a fasting blood MRS for predicting 1-hour glucose (Pearson r=0.8) and found significant associations with half-day (diurnal) postprandial glucose excursions and insulin secretion after 5-week controlled feeding interventions varying in carbohydrate amount and glycemic index. In the POUNDS Lost trial, diet-induced changes in MRSs were related to 2-year trajectories of glucose metabolism; circulating microRNAs regulating cardiometabolic abnormalities were pivotal factors influencing these changes. In the NHS, women in the top 20% of MRS had a multivariate-adjusted relative risk of 3.80 (95% CI, 2.22-6.51) for T2D and 1.48 (95% CI, 1.04-2.12) for coronary heart disease compared with those in the lowest 20%. In addition, 10-year increases in plasma metabolites related to 1-hour glucose were linearly associated with a higher risk of T2D. CONCLUSIONS: Our findings indicate that fasting blood metabolomic signatures predicting elevated 1-hour glucose reflect disease pathophysiology and could be targets for preventing T2D and coronary heart disease.

blood glucose↗

PubMed2026

Intestinal content accelerates muscle protein degradation in red shrimp (Solenocera crassicornis) during refrigeration: Insights from metagenomics and metabolomics.

This study systematically explored the effects of intestinal components on muscle quality deterioration and protein degradation of red shrimp during refrigerated storage. The results demonstrated that refrigeration induced continuous quality degradation and muscle protein breakdown in red shrimp, whereas eliminating intestinal tissues effectively retarded muscle spoilage and protein degradation, and optimized muscle texture. The intestinal microorganisms could secrete extracellular proteases to promote muscle protein degradation were primarily Vibrio, Bacillus, Pseudomonas, Photobacterium, and Shewanella. These microorganisms promote protein degradation by secreting zinc proteases, serine proteases, and aspartyl proteases. This study elucidates the molecular mechanisms of intestinal microbial metabolism influences the muscle protein degradation of red shrimp during refrigeration. The findings provide a theoretical foundation for precise regulation of intestinal-targeted microorganisms, thereby maintaining optimal quality of shrimps during refrigeration.

Animals↗

PubMed2006

Integrated metabonomic analysis of bromobenzene-induced hepatotoxicity: novel induction of 5-oxoprolinosis.

We present here a definitive metabonomic analysis in order to detect novel biomarker and metabolite information, implicating specific putative protein targets in the toxicological mechanism of bromobenzene-induced centrilobular hepatic necrosis. Male Han-Wistar rats were dosed with bromobenzene (1.5 g/kg, n = 25) and blood plasma, urine and liver samples were collected for NMR and magic angle spinning (MAS) NMR spectroscopy at various time-points postdose, with histopathology and clinical pathology performed in parallel. Liver samples were analyzed by 600 MHz 1H MAS NMR techniques and the resultant spectra were correlated to sequential 1H NMR measurements in urine and blood plasma using pattern recognition methods. 1D 1H NMR spectra were data-reduced and analyzed using principal components analysis (PCA) to show the time-dependent biochemical variations induced by bromobenzene toxicity. In addition to a holistic view of the effect of hepatic toxicity on the metabolome, a number of putative protein targets of bromobenzene and its metabolites were identified including those enzymes of the glutathione cycle, exemplified by the presence of a novel biomarker, 5-oxoproline, in liver tissue, blood plasma, and urine. As such, this work establishes the importance of metabonomics technology in resolving the mechanistic complexity of drug toxicity as well as the benefits of frontloading this approach in drug safety evaluation and biomarker discovery.

Animals↗

PubMed2005

Functional genomics by integrated analysis of metabolome and transcriptome of Arabidopsis plants over-expressing an MYB transcription factor.

The integration of metabolomics and transcriptomics can provide precise information on gene-to-metabolite networks for identifying the function of unknown genes unless there has been a post-transcriptional modification. Here, we report a comprehensive analysis of the metabolome and transcriptome of Arabidopsis thaliana over-expressing the PAP1 gene encoding an MYB transcription factor, for the identification of novel gene functions involved in flavonoid biosynthesis. For metabolome analysis, we performed flavonoid-targeted analysis by high-performance liquid chromatography-mass spectrometry and non-targeted analysis by Fourier-transform ion-cyclotron mass spectrometry with an ultrahigh-resolution capacity. This combined analysis revealed the specific accumulation of cyanidin and quercetin derivatives, and identified eight novel anthocyanins from an array of putative 1800 metabolites in PAP1 over-expressing plants. The transcriptome analysis of 22,810 genes on a DNA microarray revealed the induction of 38 genes by ectopic PAP1 over-expression. In addition to well-known genes involved in anthocyanin production, several genes with unidentified functions or annotated with putative functions, encoding putative glycosyltransferase, acyltransferase, glutathione S-transferase, sugar transporters and transcription factors, were induced by PAP1. Two putative glycosyltransferase genes (At5g17050 and At4g14090) induced by PAP1 expression were confirmed to encode flavonoid 3-O-glucosyltransferase and anthocyanin 5-O-glucosyltransferase, respectively, from the enzymatic activity of their recombinant proteins in vitro and results of the analysis of anthocyanins in the respective T-DNA-inserted mutants. The functional genomics approach through the integration of metabolomics and transcriptomics presented here provides an innovative means of identifying novel gene functions involved in plant metabolism.

Arabidopsis↗

PubMed2026

Multi-omics profiling of cerebrospinal fluid in autoimmune encephalitis: insights into pathogenesis and therapeutic targets.

BACKGROUND: Autoimmune encephalitis (AIE) is a rare, severe inflammatory brain disease, with its pathogenesis not yet fully elucidated. This study aimed to characterize proteomic and metabolomic alterations in the cerebrospinal fluid (CSF) of AIE patients and identify potential therapeutic targets. METHODS: 65 consecutive AIE patients and age-matched concurrent controls were enrolled, respectively. Clinical characteristics, including blood and CSF laboratory findings, were compared between the two groups, and CSF samples were collected for multi-omics analysis. Differentially expressed proteins (DEPs) and metabolites (DEMs) between AIE patients and controls were identified using data-independent acquisition-based proteomics and targeted liquid chromatography-mass spectrometry-based metabolomics, followed by integrated multi-omics analysis. RESULTS: Compared with controls, AIE patients had lower levels of triglyceride and C1q, but higher HDL-CH levels, neutrophil counts, and eosinophil counts in blood. CSF leukocyte, erythrocyte, lymphocyte, and mononuclear cell counts were also elevated in AIE patients. Proteomic analysis identified 163 DEPs, with enrichment of 87 canonical pathways primarily associated with immune-inflammatory responses, neuronal-synaptic dysfunction, and cell signaling and metabolic pathways. Metabolomic analysis recognized 21 DEMs, predominantly amino acids, lipids, and carbohydrates, which were involved in lipid-carbohydrate metabolism and immune regulation. Integrated multi-omics analysis validated these findings and identified several potential therapeutic targets for AIE, including the IL6-STAT3 axis. CONCLUSIONS: Integrated multi-omics analysis systematically delineates cellular and molecular alterations underlying AIE. Immune-inflammatory response and lipid metabolism are pivotal in AIE progression and the IL6-STAT3 axis holds promise as a potential therapeutic target.

Humans↗

PubMed2003

Factors affecting the robustness of metabolite fingerprinting using 1H NMR spectra.

1H NMR spectroscopy is one of the techniques whose potential is currently being explored in the emerging field of metabolomics. It is a non-targeted method, producing signals for all proton-containing chemical species. For crude plant materials the spectra are always complex, with many signals overlapping. Hence a most suitable approach for analysing them is 'metabolite fingerprinting', which is aimed at highlighting compositional similarities and exploring the overall natural variability in a population of samples. The most commonly used method for this is principal component analysis (PCA), as it allows the whole spectral trace to be analysed and the vast quantity of information to be simplified. In this paper we investigate whether there are factors which may affect the NMR spectra in a way that subsequently decreases the robustness of the metabolite fingerprinting by PCA. Imperfections in the signal registration (i.e. inconsistency of the peak position) are generally detrimental to analysing whole traces by multivariate methods. The sources of such problems are illustrated through specially designed repeatability studies using potato and tomato samples, and the analysis of a tea dataset containing many samples. Careful sample preparation can help to limit peak shifts; for instance here by attempting to control the pH of the extracts. In addition, some compounds are susceptible to interactions affecting their chemical shifts and mathematical alignment of peaks may be necessary. Lastly factors such as resolution can also affect analyses and must be carefully adjusted. Our choice of examples aims to raise awareness of potential problems. We do not question the validity of the NMR approach, but point out those areas where special care may need to be taken.

Databases, Factual↗