A high-performance liquid chromatography-tandem mass spectrometry method for quantitation of nitrogen-containing intracellular metabolites

Metabolomic Analysis and in Vitro Investigation of the Biological Properties of a By-Product Derived from Vicia faba

By-products from plant sources are recently regarded as a valuable source of bioactive compounds. In this regard, the present study aims to assess the bioactivities of the 70 % MeOH extract obtained from Vicia faba peels and analyze its metabolomic profile. Acetylcholinesterase and carbohydrate metabolizing enzymes inhibitory activities of the plant extract were assayed using quantitative colorimetric tests. Antioxidant activity was estimated by DPPH assay, and cytotoxic activity was evaluated against normal fibroblast skin cells (1-BJ1). Ninety-one metabolites were tentatively identified using ultra-high-performance liquid chromatography (UHPLC) hyphenated with quadrupole-time-of-flight tandem mass spectrometry (QTOF-MS). Most of these compounds were described for the first time in the plant. In addition, catechin, rutin, quercitrin, and rhamnetin were isolated from the plant extract. The plant extract and the isolated compounds possessed no cytotoxic activity on (1-BJ1), while they exhibited anticholinesterase with the highest activity for 70 % MeOH extract (IC50 =120.11 mg/L), antioxidant potential with the highest activity for rutin (90.54±0.73 %), and carbohydrate metabolizing inhibitory activities with the highest activity for rutin. These discoveries imply that V. faba peels might serve as an efficient antioxidant, exhibit anticholinesterase properties, and have the potential for use in managing diabetes, all while avoiding cytotoxicity in normal cells.

Ocean acidification causes fundamental changes in the cellular metabolism of the Arctic copepod Calanus glacialis as detected by metabolomic analysis

Using a targeted metabolomic approach we investigated the effects of low seawater pH on energy metabolism in two late copepodite stages (CIV and CV) of the keystone Arctic copepod species Calanus glacialis. Exposure to decreasing seawater pH (from 8.0 to 7.0) caused increased ATP, ADP and NAD⁺ and decreased AMP concentrations in stage CIV, and increased ATP and phospho-L-arginine and decreased AMP concentrations in stage CV. Metabolic pathway enrichment analysis showed enrichment of the TCA cycle and a range of amino acid metabolic pathways in both stages. Concentrations of lactate, malate, fumarate and alpha-ketoglutarate (all involved in the TCA cycle) increased in stage CIV, whereas only alpha-ketoglutarate increased in stage CV. Based on the pattern of concentration changes in glucose, pyruvate, TCA cycle metabolites, and free amino acids, we hypothesise that ocean acidification will lead to a shift in energy production from carbohydrate metabolism in the glycolysis toward amino acid metabolism in the TCA cycle and oxidative phosphorylation in stage CIV. In stage CV, concentrations of most of the analysed free fatty acids increased, suggesting in particular that ocean acidification increases the metabolism of stored wax esters in this stage. Moreover, aminoacyl-tRNA biosynthesis was enriched in both stages indicating increased enzyme production to handle low pH stress.

OUP accepted manuscript

HPLC-PDA, LC-MS/MS methods were developed for simultaneous determination of a group of oxidative stress biomarkers (OSBs); 2dA, 2dC, 2dU, 3NLT, 5HMU and 8OHdG in 10 simulated artificial body fluids. O-phosphoric acid and methanol composed mobile phases A and B for gradient elution in HPLC-PDA using ODS-2 column. Linearity obtained for 1.0×10-6-1.0×10-4M range. LODs were 1.73×10-6, 1.19×10-6, 2.59×10-6, 1.40×10-6, 2.21×10-6 and 4.07×10-6M for 2dU, 8OHdG, 2dA, 2dC, 5HMU and 3NLT, respectively. LOQs were 5.29×10-6, 4.02×10-6, 6.82×10-6, 4.02×10-6, 6.82×10-6 and 9.92×10-6M. About 10 mM aqueous ammonium acetate solution and methanol containing 0.1% (v/v) formic acid composed mobile phases A and B for gradient elution in LC-MS/MS. Linearity obtained for 1.0×10-8-1.0×10-6M range. LODs were 2.88×10-10, 1.01×10-8, 3.38×10-9, 1.36×10-7, 1.81×10-7 and 1.40×10-8M for 2dU, 8OHdG, 2dA, 2dC, 5HMU and 3NLT, respectively. LOQs were 9.37×10-10, 3.22×10-8, 1.91×10-8, 4.53×10-7, 5.90×10-7 and 2.18×10-8M. Both methods were validated using ICH Q2(R1) guideline. Specificity, linearity, range, accuracy, precision, reproducibility, LOD, LOQ and recovery were achieved. Chemometric analysis was performed on raw PDA and MS data to check their significance for discrimination of OSBs. Sets of single and triple quadrupole fragmentations were evaluated for principle component analysis. Chosen number of PCs successfully distinguished OSBs of interest.

GCN2 adapts protein synthesis to scavenging-dependent growth

Pancreatic cancer cells with limited access to free amino acids can grow by scavenging extracellular protein. In a murine model of pancreatic cancer, we performed a genome-wide CRISPR screen for genes required for scavenging-dependent growth. The screen identified key mediators of macropinocytosis, peripheral lysosome positioning, endosome-lysosome fusion, lysosomal protein catabolism, and translational control. The top hit was GCN2, a kinase that suppresses translation initiation upon amino acid depletion. Using isotope tracers, we show that GCN2 is not required for protein scavenging. Instead, GCN2 prevents ribosome stalling but without slowing protein synthesis; cells still use all of the limiting amino acids as they emerge from lysosomes. GCN2 also adapts gene expression to the nutrient-poor environment, reorienting protein synthesis away from ribosomes and toward lysosomal hydrolases, such as cathepsin L. GCN2, cathepsin L, and the other genes identified in the screen are potential therapeutic targets in pancreatic cancer.

Tolerant Larvae and Sensitive Juveniles: Integrating Metabolomics and Whole-Organism Responses to Define Life-Stage Specific Sensitivity to Ocean Acidification in the American Lobster

Bentho-pelagic life cycles are the dominant reproductive strategy in marine invertebrates, providing great dispersal ability, access to different resources, and the opportunity to settle in suitable habitats upon the trigger of environmental cues at key developmental moments. However, free-dispersing larvae can be highly sensitive to environmental changes. Among these, the magnitude and the occurrence of elevated carbon dioxide (CO₂) concentrations in oceanic habitats is predicted to exacerbate over the next decades, particularly in coastal areas, reaching levels beyond those historically experienced by most marine organisms. Here, we aimed to determine the sensitivity to elevated pCO₂ of successive life stages of a marine invertebrate species with a bentho-pelagic life cycle, exposed continuously during its early ontogeny, whilst providing in-depth insights on their metabolic responses. We selected, as an ideal study species, the American lobster Homarus americanus, and investigated life history traits, whole-organism physiology, and metabolomic fingerprints from larval stage I to juvenile stage V exposed to different pCO₂ levels. Current and future ocean acidification scenarios were tested, as well as extreme high pCO₂/low pH conditions that are predicted to occur in coastal benthic habitats and with leakages from underwater carbon capture storage (CCS) sites. Larvae demonstrated greater tolerance to elevated pCO₂, showing no significant changes in survival, developmental time, morphology, and mineralisation, although they underwent intense metabolomic reprogramming. Conversely, juveniles showed the inverse pattern, with a reduction in survival and an increase in development time at the highest pCO₂ levels tested, with no indication of metabolomic reprogramming. Metabolomic sensitivity to elevated pCO₂ increased until metamorphosis (between larval and juvenile stages) and decreased afterward, suggesting this transition as a metabolic keystone for marine invertebrates with complex life cycles.

Pyrrolizidine alkaloids in tea, herbal tea and iced tea beverages- survey and transfer rates

The transfer rate of 37 pyrrolizidine alkaloids (PA) found in ten naturally contaminated teas and herbal teas to their brews was studied in detail. Mixed herbal, peppermint, red bush, senna, black tea and green tea infusions were prepared according to the ISO guide and vendor's instructions, respectively, and parameters like herb-to-water ratio, steeping time and multiple extractions studied. In general, a transfer rate of 38-100% (median 95%) for brews following vendor's instructions was determined. The total concentration range of PA in these ten samples was 154-2412 ng/g (median 422 ng/g) in the herb and for single analytes 0.1-170 ng/g. Seven of the 37 PA occurred unexpectedly; these were tentatively identified and quantified by liquid chromatography-high resolution mass spectrometry (LC-HR-MS), since their contributions to total PA-content matter. Additionally, 46 iced tea beverages were analysed for their PA-load, determined to be in the range 0-631 ng/L (median 40 ng/L). The applied solid-phase extraction (SPE) clean-up turned out to be capable of separating PA in the free base pyrrolizidine alkaloids (PAFB) and their N-oxides (PANO) in a two-step elution, which was a valuable tool to support identification of unexpected PA. Further, atropine was found in 50% of the ten tea herb samples (range: 1-4 ng/g) and in 13% of the iced tea beverage samples (range: 2-65 ng/L).

Quantitative Bioreactor Monitoring of Intracellular Bacterial Metabolites in Clostridium autoethanogenum Using Liquid Chromatography-Isotope Dilution Mass Spectrometry

We report a liquid chromatography-isotope dilution mass spectrometry method for the simultaneous quantification of 131 intracellular bacterial metabolites of Clostridium autoethanogenum. A comprehensive mixture of uniformly ¹³C-labeled internal standards (U-¹³C IS) was biosynthesized from the closely related bacterium Clostridium pasteurianum using 4% ¹³C-glucose as a carbon source. The U-¹³C IS mixture combined with ¹²C authentic standards was used to validate the linearity, precision, accuracy, repeatability, limits of detection, and quantification for each metabolite. A robust-fitting algorithm was employed to reduce the weight of the outliers on the quantification data. The metabolite calibration curves were linear with R ² ≥ 0.99, limits of detection were ≤1.0 μM, limits of quantification were ≤10 μM, and precision/accuracy was within RSDs of 15% for all metabolites. The method was subsequently applied for the daily monitoring of the intracellular metabolites of C. autoethanogenum during a CO gas fermentation over 40 days as part of a study to optimize biofuel production. The concentrations of the metabolites were estimated at steady states of different pH levels using the robust-fitting mathematical approach, and we demonstrate improved accuracy of results compared to conventional regression. Metabolic pathway analysis showed that reactions of the incomplete (branched) tricarboxylic acid "cycle" were the most affected pathways associated with the pH shift in the bioreactor fermentation of C. autoethanogenum and the concomitant changes in ethanol production.

The effect of feeding adequate or deficient vitamin B6 or folic acid to breeders on methionine metabolism in 18-day-old chick embryos

Three isotopic tracers ([2,3,3-²H₃]-L-serine, [²H₁₁]-L-betaine, and [1-¹³C]-L-methionine) were administered by amnion injection into 18-day-old chick embryos to investigate the kinetics of methionine metabolism. The embryos utilized were from eggs collected from 34-week-old Cobb 500 broiler breeders that were fed either a control diet containing folic acid (1.25 mg/kg diet) and pyridoxine HCl (5 mg/kg diet) or diets devoid of supplemental pyridoxine or folic acid. Intermediate metabolites of methionine metabolism and polyamines were analyzed in 18-day-old chick embryos. There were no differences in hepatic [²H₂] methionine or [²H₃] cysteine enrichments or in physiological concentrations of sulfur amino acids for chick embryos from breeders fed the control diet and embryos from breeders fed diets containing no pyridoxine or folic acid. Supplementation of B₆ or folic acid did not affect the production of methionine and cysteine in chick embryos. However, breeders fed the control diet with both folic acid and pyridoxine supplementation produced embryos with a two-fold reduction of hepatic homocysteine and increased spermine compared with embryos from breeders fed diets containing no supplemental pyridoxine or folic acid (P < 0.05). Hepatic S-adenosylmethionine for embryos from breeders fed no supplemental B₆ was half the concentration compared with embryos from breeders fed the control diet. Embryos from breeders fed the control diet were utilized to determine the proportion of homocysteine going through remethylation and transsulfuration and also to determine the pathway of remethylation. Sixty-five percent of the methyl groups used for homocysteine remethylation from control embryos was via the MFMT pathway. Alternatively, 61% of homocysteine from control embryos was remethylated via the MFMT and the BHMT reactions and 39% of homocysteine was catabolized to cysteine via the transsulfuration pathway. These data show that in embryos, intermediate metabolites of methionine and polyamines increase in concentration when pyridoxine levels are provided in deficient concentrations to the breeder hen. In addition, this research demonstrates that folic acid deficient embryos conserve methionine, rather than catabolize it to cysteine.

Liquid Chromatography Methods for Separation of Polar and Charged Intracellular Metabolites for 13C Metabolic Flux Analysis

Accurate quantification of mass isotopolog distribution (MID) of intracellular metabolites is a key requirement for ¹³C metabolic flux analysis (¹³C-MFA). Liquid chromatography coupled with mass spectrometry (LC/MS) has emerged as a frontrunner technique that combines two orthogonal separation strategies. While metabolomics requires separation of monoisotopic peaks, ¹³C-MFA imposes additional demands for chromatographic separation as isotopologs of metabolites significantly add to the number of analytes. In this protocol chapter, we discuss two liquid chromatography methods, namely, reverse phase ion-pairing and hydrophilic interaction chromatography (HILIC) that together can separate a wide variety of metabolites that are typically used for ¹³C metabolic flux analysis.

Anthocyanin Profiling of Maize Grains Using DIESI-MSQD Reveals That Cyanidin-Based Derivatives Predominate in Purple Corn, whereas Pelargonidin-Based Molecules Occur in Red-Pink Varieties from Mexico

Corn seeds contain natural pigments and antioxidants, such as the molecular variants of flavonoids and carotenoids. The aleurone and pericarp tissues from pigmented genotypes were extracted for metabolic fingerprinting and evaluated using UV-vis and mass spectrometry (MS). MS ionomic fingerprints classified samples according to genetic background and kernel color. The MS/MS fragmentation pattern (Daughter and Neutral Loss methods) allowed the tentative identification of 18 anthocyanins with glycosyl, malonyl, and succinyl moieties, including 535 m/z for cyanidin-3-O-(6″-malonyl-glucoside) and 621 m/z for cyanidin-3-O-(3″,6″-dimalonyl-glucoside). We also detected 663 m/z for pelargonidin-3-O-(disuccinyl-glucoside) and 633 m/z for peonidin-3-O-(disuccinyl-glucoside). Cyanidin-based anthocyanins were the most abundant in dark purple colored kernels, while pelargonidins predominated in the red-pink kernels of the "Elote occidental" landrace. Grains of "Conico negro" had a simultaneous pigmentation of aleurone and pericarp, while Vitamaize had purple pigmentation only in the aleurone layer. Most landraces had a white endosperm, while Vitamaize had a yellow endosperm and a dark seed coat. We conclude that Vitamaize grains contain both carotenes and anthocyanins, and therefore it is proposed as a nontransgenic agronomically improved variety of tropical purple maize, a good source for organic superfoods.

Diazo Reagent Labeling with Mass Spectrometry Analysis for Sensitive Determination of Ribonucleotides in Living Organisms

Ribonucleotide analogues and their related phosphorylated metabolites play critical roles in tumor metabolism. However, determination of the endogenous ribonucleotides from the complex biological matrix is still a challenge due to their high structural similarity and high polarity that will lead to the low retention and low detection sensitivities by liquid chromatogram mass spectrometry analysis. In this study, we developed the diazo reagent labeling strategy with mass spectrometry analysis for sensitive determination of ribonucleotides in the living organism. A pair of light and heavy stable isotope labeling reagents, 2-(diazomethyl)-N-methyl-N-phenyl-benzamide (2-DMBA) and d₅-2-(diazomethyl)-N-methyl-N-phenyl-benzamide (d₅-2-DMBA), were synthesized to label ribonucleotides. 2-DMBA showed high specificity and high efficiency for the labeling of ribonucleotides. Our results demonstrated that the detection sensitivities of 12 ribonucleotides increased by 17-174-fold upon 2-DMBA labeling. The obtained limits of detection (LODs) of ribonucleotides ranged from 0.07 fmol to 0.41 fmol. Using this method, we achieved the sensitive and accurate detection of ribonucleotides from only a few cells (8 cells). To the best of our knowledge, this is the highest detection sensitivity for ribonucleotides ever reported. In addition, we found that the contents of almost all of these ribonucleotides were significantly increased in human breast carcinoma tissues compared to tumor-adjacent normal tissues, suggesting that endogenous ribonucleotides may play certain functional roles in the regulation of cancer development and formation. This method also can be potentially applied in the analysis of phosphorylated compounds.

Phosphatidylcholine Biosynthesis in Mitis Group Streptococci via Host Metabolite Scavenging

We lack fundamental information about the composition of the cellular membrane even for the best-studied pathogens of critical significance for human health. The mitis group streptococci are closely linked to humans in health and disease, but their membrane biology is poorly understood. Here, we demonstrate that these streptococci scavenge major human metabolites and use them to synthesize the membrane phospholipid PC. Our work is significant because it identifies a mechanism by which the major human pathogen S. pneumoniae and the primary human oral colonizers S. mitis and S. oralis remodel their membranes in response to host metabolites.

The mitis group streptococci include the major human pathogen Streptococcus pneumoniae and the opportunistic pathogens Streptococcus mitis and Streptococcus oralis, which are human oral cavity colonizers and agents of bacteremia and infective endocarditis in immunocompromised patients. Bacterial membrane lipids play crucial roles in microbe-host interactions; for many pathogens, however, the composition of the membrane is poorly understood. In this study, we characterized the lipidomes of selected species of mitis group streptococci and investigated the mechanistic basis for biosynthesis of the phospholipid phosphatidylcholine (PC). PC is a major lipid in eukaryotic cellular membranes, but it is considered to be comparatively rare in bacterial taxa. Using liquid chromatography-mass spectrometry in conjunction with stable isotope tracing, we determined that mitis group streptococci synthesize PC via a rare host-metabolite-scavenging pathway, the glycerophosphocholine (GPC) pathway, which is largely uncharacterized in bacteria. Our work demonstrates that mitis group streptococci, including S. pneumoniae, remodel their membranes in response to the major human metabolites GPC and lysophosphatidylcholine.

IMPORTANCE We lack fundamental information about the composition of the cellular membrane even for the best-studied pathogens of critical significance for human health. The mitis group streptococci are closely linked to humans in health and disease, but their membrane biology is poorly understood. Here, we demonstrate that these streptococci scavenge major human metabolites and use them to synthesize the membrane phospholipid PC. Our work is significant because it identifies a mechanism by which the major human pathogen S. pneumoniae and the primary human oral colonizers S. mitis and S. oralis remodel their membranes in response to host metabolites.

Isotopic ratio outlier analysis improves metabolomics prediction of nitrogen treatment in maize

We evaluated Isotope Ratio Outlier Analysis (IROA) as a metabolome-wide internal standard approach to improve the quality of LC/MS data collected from a large-scale greenhouse experiment designed to metric the ability of metabolomics to model quantitatively nitrogen treatments. We further looked at how IROA would be incorporated into a metabolomics workflow. For this we compared IROA processed data with that generated without the benefit of metabolome-wide internal standards using our current tool, Genedata Expressionist, from the same raw LC/MS data files. In our experiment, 367 maize plants were grown from kernel in a greenhouse under controlled conditions. Plants were treated from germination on with varying concentrations of nutrient nitrogen as one (treatment) variable. A second variable was the presence of one of two transgenes. Metabolomics analysis of leaves was performed by LC/MS positive and negative electrospray ionization modes, and raw data were processed with both our routine and IROA protocols. IROA data analysis detected 184 metabolites in each ionization mode. Analysis without IROA yielded 281 metabolites in positive ionization mode and 172 in negative ionization mode. Data from both protocols were normalized for sample dry weight, location in the greenhouse, extraction batch, sample run order, and internal standard. Normalized results were subjected to partial least squares (PLS) analysis to model the relationship between the metabolome and nitrogen treatment. Without IROA, regression coefficients of 0.819 and 0.849 for positive and negative modes, respectively were achieved. The IROA protocol improved on the values, yielding regression coefficients of 0.876 and 0.879 for positive and negative modes, respectively. In addition, IROA corrected for detector saturation for several high abundant peaks. Our experiment demonstrates that incorporating IROA into an LC/MS metabolomics experiment improves data quality and facilitates more precise modeling of a biological response.

Modulatory effect of Prosopis juliflora leaves on hepatic fibrogenic and fibrolytic alterations induced in rats by thioacetamide

This study investigated the antifibrotic effect of Prosopis juliflora leaves crude methanolic extract (PJEL) against thioacetamide (TAA)-induced liver fibrosis. The phytochemical analysis of PJEL was performed via HPLC/MS in association with evaluating its free radical scavenging and cytotoxic activities. The antifibrotic activity of PJEL was assessed by dividing Wistar rats into 8 groups: normal control, PJEL1-administered rats (2 mg/ Kg b.w.), PJEL2-administered rats (4 mg/ Kg b.w.), PJEL3-administered rats (8 mg/Kg b.w.), TAA-induced hepatic fibrosis, TTA + PJEL1, TAA + PJEL2, and TAA + PJEL3. Results indicated that PJEL crude methanolic extract is rich in polyphenolic compounds and alkaloids. PJEL exerted free radical scavenging activity with IC₅₀ of 123.5 μg/mL and cytotoxic activity against a well-differentiated hepatocellular cell line (IC₅₀ = 11.1 μg/mL). PJEL at a dose of 4 mg/Kg b.w. ameliorated serum ALT activity and improved serum albumin level and hepatic hydroxyproline content in association with a reduction in the fibrosis stage. PJEL elevated hepatic tumor necrosis factor-α and interleukin-6 contents with less necrosis grade. PJEL post-therapy ameliorated the relative expression of Bcl-2, Col1A1, Mmp-9, and Mmp-2 genes in liver. CONCLUSION: PJEL possesses a good therapeutic activity against TAA-induced liver fibrosis via enhancing extracellular matrix removal and stimulating hepatic regeneration to decrease hepatic necrosis.

Isocitrate dehydrogenase 1 and 2 mutations, 2-hydroxyglutarate levels, and response to standard chemotherapy for patients with newly diagnosed acute myeloid leukemia

BACKGROUND

Acute myeloid leukemia (AML) cells harboring mutations in isocitrate dehydrogenase 1 (IDH1) and isocitrate dehydrogenase 2 (IDH2) produce the oncometabolite 2-hydroxyglutarate (2HG). This study prospectively evaluated the 2HG levels, IDH1/2 mutational status, and outcomes of patients receiving standard chemotherapy for newly diagnosed AML.

METHODS

Serial samples of serum, urine, and bone marrow aspirates were collected from patients newly diagnosed with AML, and 2HG levels were measured with mass spectrometry. Patients with baseline serum 2HG levels greater than 1000 ng/mL or marrow pellet 2HG levels greater than 1000 ng/2 × 10⁶ cells, which suggested the presence of an IDH1/2 mutation, underwent serial testing. IDH1/2 mutations and estimated variant allele frequencies were identified. AML characteristics were compared with the Wilcoxon test and Fisher's exact test. Disease-free survival and overall survival (OS) were evaluated with log-rank tests and Cox regression.

RESULTS

Two hundred and two patients were treated for AML; 51 harbored IDH1/2 mutations. IDH1/2-mutated patients had significantly higher 2HG levels in serum, urine, bone marrow aspirates, and aspirate cell pellets than wild-type patients. A serum 2HG level greater than 534.5 ng/mL was 98.8% specific for the presence of an IDH1/2 mutation. Patients with IDH1/2-mutated AML treated with 7+3-based induction had a 2-year event-free survival (EFS) rate of 44% and a 2-year OS rate of 57%. There was no difference in complete remission rates, EFS, or OS between IDH1/2-mutated and wild-type patients. Decreased serum 2HG levels on day 14 as a proportion of the baseline were significantly associated with improvements in EFS (P = .047) and OS (P = .019) in a multivariate analysis.

CONCLUSIONS

Among patients with IDH1/2-mutated AML, 2HG levels are highly specific for the mutational status at diagnosis, and they have prognostic relevance in patients receiving standard chemotherapy.

Structural and Functional Analysis of the Gut Microbiome for Toxicologists

Characterizing the reciprocal interactions between toxicants, the gut microbiota, and the host, holds great promise for improving our mechanistic understanding of toxic endpoints. Advances in culture-independent sequencing analysis (e.g., 16S rRNA gene amplicon sequencing) combined with quantitative metabolite profiling (i.e., metabolomics) have provided new ways of studying the gut microbiome and have begun to illuminate how toxicants influence the structure and function of the gut microbiome. Developing a standardized protocol is important for establishing robust, reproducible, and importantly, comparative data. This protocol can be used as a foundation for examining the gut microbiome via sequencing-based analysis and metabolomics. Two main units follow: (1) analysis of the gut microbiome via sequencing-based approaches; and (2) functional analysis of the gut microbiome via metabolomics. © 2018 by John Wiley & Sons, Inc.

Recent advances in cancer metabolism: a technological perspective

Cancer cells are highly dependent on metabolic pathways to sustain both their proliferation and adaption to harsh microenvironments. Thus, understanding the metabolic reprogramming that occurs in tumors can provide critical insights for the development of therapies targeting metabolism. In this review, we will discuss recent advancements in metabolomics and other multidisciplinary techniques that have led to the discovery of novel metabolic pathways and mechanisms in diverse cancer types.

Researchers now have access to a rapidly growing number of tools for probing the metabolic abnormalities associated with tumor growth. Unrestrained growth puts special demands on cancer cells, and scientists have known for nearly a century that tumor metabolism differs considerably from healthy tissue metabolism. Gina DeNicola and colleagues at the Moffitt Cancer Center and Research Institute, Tampa, USA, have reviewed the technological tools available for monitoring the molecules that power cell growth and survival. These include mass spectrometry, which can generate an extremely detailed census of cellular metabolites in a single experiment. The authors also highlight techniques that can help ‘trap’ short-lived or unstable chemical intermediates for analysis. Other chemical labeling and tracing techniques can illuminate activity of selected metabolic processes in living tumor cells or even in patients, findings that could reveal therapeutic vulnerabilities.

Modified nucleoside triphosphates exist in mammals

By establishing a chemical labeling method in combination with liquid chromatography-mass spectrometry analysis, we reported the widespread existence of various modified nucleoside triphosphates in eukaryotes.

DNA and RNA contain diverse chemical modifications that exert important influences in a variety of cellular processes. In addition to enzyme-mediated modifications of DNA and RNA, previous in vitro studies showed that pre-modified nucleoside triphosphates (NTPs) can be incorporated into DNA and RNA during replication and transcription. Herein, we established a chemical labeling method in combination with liquid chromatography-electrospray ionization-mass spectrometry (LC-ESI-MS) analysis for the determination of endogenous NTPs in the mammalian cells and tissues. We synthesized 8-(diazomethyl)quinoline (8-DMQ) that could efficiently react with the phosphate group under mild condition to label NTPs. The developed method allowed sensitive detection of NTPs, with the detection limits improved by 56–137 folds. The results showed that 12 types of endogenous modified NTPs were distinctly determined in the mammalian cells and tissues. In addition, the majority of these modified NTPs exhibited significantly decreased contents in human hepatocellular carcinoma (HCC) tissues compared to tumor-adjacent normal tissues. Taken together, our study revealed the widespread existence of various modified NTPs in eukaryotes.

Quantitative Isotope-Dilution High-Resolution-Mass-Spectrometry Analysis of Multiple Intracellular Metabolites in Clostridium autoethanogenum with Uniformly 13C-Labeled Standards Derived from Spirulina

We have investigated the applicability of commercially available lyophilized spirulina ( Arthrospira platensis), a microorganism uniformly labeled with ¹³C, as a readily accessible source of multiple ¹³C-labeled metabolites suitable as internal standards for the quantitative determination of intracellular bacterial metabolites. Metabolites of interest were analyzed by hydrophilic-interaction liquid chromatography coupled with high-resolution mass spectrometry. Multiple internal standards obtained from uniformly (U)-¹³C-labeled extracts from spirulina were used to enable isotope-dilution mass spectrometry (IDMS) in the identification and quantification of intracellular metabolites. Extraction of the intracellular metabolites of Clostridium autoethanogenum using 2:1:1 chloroform/methanol/water was found to be the optimal method in comparison with freeze-thaw, homogenization, and sonication methods. The limits of quantification were ≤1 μM with excellent linearity for all of the calibration curves ( R² ≥ 0.99) for 74 metabolites. The precision and accuracy were found to be within relative standard deviations (RSDs) of 15% for 49 of the metabolites and within RSDs of 20% for all of the metabolites. The method was applied to study the effects of feeding different levels of carbon monoxide (as a carbon source) on the central metabolism and Wood-Ljungdahl pathway of C. autoethanogenum grown in continuous culture over 35 days. Using LC-IDMS with U-¹³C spirulina allowed the successful quantification of 52 metabolites in the samples, including amino acids, carboxylic acids, sugar phosphates, purines, and pyrimidines. The method provided absolute quantitative data on intracellular metabolites that was suitable for computational modeling to understand and optimize the C. autoethanogenum metabolic pathways active in gas fermentation.

mTOR Inhibition Restores Amino Acid Balance in Cells Dependent on Catabolism of Extracellular Protein

Scavenging of extracellular protein via macropinocytosis is an alternative to monomeric amino acid uptake. In pancreatic cancer, macropinocytosis is driven by oncogenic Ras signaling and contributes substantially to amino acid supply. While Ras signaling promotes scavenging, mTOR signaling suppresses it. Here, we present an integrated experimental-computational method that enables quantitative comparison of protein scavenging rates across cell lines and conditions. Using it, we find that, independently of mTORC1, amino acid scarcity induces protein scavenging and that under such conditions the impact of mTOR signaling on protein scavenging rate is minimal. Nevertheless, mTOR inhibition promotes growth of cells reliant on eating extracellular protein. This growth enhancement depends on mTORC1's canonical function in controlling translation rate: mTOR inhibition slows translation, thereby matching protein synthesis to the limited amino acid supply. Thus, paradoxically, in amino acid-poor conditions the pro-anabolic effects of mTORC1 are functionally opposed to growth.

Bisphosphoglycerate mutase controls serine pathway flux via 3-phosphoglycerate

Lower glycolysis involves a series of reversible reactions, which interconvert intermediates that also feed anabolic pathways. 3-phosphoglycerate (3-PG) is an abundant lower glycolytic intermediate that feeds serine biosynthesis via the enzyme phosphoglycerate dehydrogenase, which is genomically amplified in several cancers. Phosphoglycerate mutase (PGAM1) catalyzes the isomerization of 3-PG into the downstream glycolytic intermediate 2-phosphoglycerate (2-PG). Catalytic activity of PGAM1 requires its histidine phosphorylation. We show that the primary PGAM1 histidine phosphate donor is 2,3-bisphosphoglycerate (2,3-BPG), which is made from the glycolytic intermediate 1,3-bisphosphoglycerate (1,3-BPG) by bisphosphoglycerate mutase (BPGM). When BPGM is knocked out, 1,3-BPG can directly phosphorylate PGAM1. In this case, PGAM1 phosphorylation and activity are decreased, but nevertheless sufficient to maintain normal glycolytic flux and cellular growth rate. 3-PG, however, accumulates, leading to increased serine synthesis. Thus, one biological function of BPGM is to control glycolytic intermediate levels and thereby serine biosynthetic flux.

Comparing the impact of ultrafine particles from petrodiesel and biodiesel combustion to bacterial metabolism by targeted HPLC-MS/MS metabolic profiling

Alterations of gut bacterial metabolism play an important role in their host metabolism, and can result in diseases such as obesity and diabetes. While many factors were discovered influencing the gut bacterial metabolism, exposure to ultrafine particles (UFPs) from engine combustions were recently proposed to be a potential risk factor for the perturbation of gut bacterial metabolism, and consequentially to obesity and diabetes development. This study focused on evaluation of how UFPs from diesel engine combustions impact gut bacterial metabolism. We hypothesize that UFPs from different type of diesel (petrodiesel vs. biodiesel) will both impact bacterial metabolism, and the degree of impact is also diesel type-dependent. Targeted metabolic profiling of 221 metabolites were applied to three model gut bacteria in vitro, Streptococcus salivarius, Lactobacillus acidophilus and Lactobacillus fermentum. UFPs from two types of fuels, petrodiesel (B0) and a biodiesel blend (B20: 20% soy biodiesel/80% B0 by volume), were exposed to the bacteria and their metabolic changes were compared. For each bacterial strain, metabolites with significantly changed abundance were observed in both perturbations, and all three strains have increased number of altered metabolites detected from B20 UFPs perturbation in comparison to B0 UFPs. Multivariate statistical analysis further confirmed that the metabolic profiles were clearly different between testing groups. Metabolic pathway analyses also demonstrated several important metabolic pathways, including pathways involves amino acids biosynthesis and sugar metabolism, were significantly impacted by UFPs exposure.

Determination and quantification of intracellular fludarabine triphosphate, cladribine triphosphate and clofarabine triphosphate by LC-MS/MS in human cancer cells

Purine nucleoside analogues are widely used in the treatment of haematological malignancies, and their biological activity is dependent on the intracellular accumulation of their triphosphorylated metabolites. In this context, we developed and validated a liquid chromatography tandem mass spectrometry (LC-MS/MS) method to study the formation of 5'-triphosphorylated derivatives of cladribine, fludarabine, clofarabine and 2'-deoxyadenosine in human cancer cells. Br-ATP was used as internal standard. Separation was achieved on a hypercarb column. Analytes were eluted with a mixture of hexylamine (5 mM), DEA (0.4%, v/v, pH 10.5) and acetonitrile, in a gradient mode at a flow rate of 0.3mLmin^-1. Multiple reactions monitoring (MRM) and electrospray ionization in negative mode (ESI-) were used for detection. The application of this method to the quantification of these phosphorylated cytotoxic compounds in a human follicular lymphoma cell line, showed that it was suitable for the study of relevant biological samples.

Formation and Determination of Endogenous Methylated Nucleotides in Mammals by Chemical Labeling Coupled with Mass Spectrometry Analysis

5-Methylcytosine (5-mC) is an important epigenetic mark that plays critical roles in a variety of cellular processes. To properly exert physiological functions, the distribution of 5-mC needs to be tightly controlled in both DNA and RNA. In addition to methyltransferase-mediated DNA and RNA methylation, premethylated nucleotides can be potentially incorporated into DNA and RNA during replication and transcription. To exclude the premodified nucleotides into DNA and RNA, endogenous 5-methyl-2'-deoxycytidine monophosphate (5-Me-dCMP) generated from nucleic acids metabolism can be enzymatically deaminated to thymidine monophosphate (TMP). Therefore, previous studies failed to detect 5-Me-dCMP or 5-methylcytidine monophosphate (5-Me-CMP) in cells. In the current study, we established a method by chemical labeling coupled with liquid chromatography-electrospray ionization mass spectrometry (LC-ESI-MS/MS) for sensitive and simultaneous determination of 10 nucleotides, including 5-Me-dCMP and 5-Me-CMP. As N,N-dimethyl-p-phenylenediamine (DMPA) was utilized for labeling, the detection sensitivities of nucleotides increased by 88-372-fold due to the introduction of a tertiary amino group and a hydrophobic moiety from DMPA. Using this method, we found that endogenous 5-Me-dCMP and 5-Me-CMP widely existed in cultured human cells, human tissues, and human urinary samples. The presence of endogenous 5-Me-dCMP and 5-Me-CMP indicates that deaminases may not fully deaminate these methylated nucleotides. Consequently, the remaining premethylated nucleosides could be converted to nucleoside triphosphates as building blocks for DNA and RNA synthesis. Furthermore, we found that the contents of 5-Me-dCMP and 5-Me-CMP exhibited significant decreases in renal carcinoma tissues and urine samples of lymphoma patients compared to their controls, probably due to more reutilization of methylated nucleotides in DNA and RNA synthesis. This study is, to the best of our knowledge, the first report for detecting endogenous 5-Me-dCMP and 5-Me-CMP in mammals. The detectable endogenous methylated nucleotides indicate the potential deleterious effects of premodified nucleotides on aberrant gene regulation in cancers.

LC-MS/MS method for quantitation of seven biomarkers in human plasma for the assessment of insulin resistance and impaired glucose tolerance

Early detection of insulin resistance (IR) and/or impaired glucose tolerance (IGT) is crucial for delaying and preventing the progression toward type 2 diabetes. We recently developed and validated a straightforward metabolite-based test for the assessment of IR and IGT in a single LC-MS/MS method. Plasma samples were diluted with isotopically-labeled internal standards and extracted by simple protein precipitation. The extracts were analyzed by LC-MS/MS for the quantitation of 2-hydroxybutyric acid (0.500-40.0μg/mL), 3-hydroxybutyric acid (1.00-80.0μg/mL), 4-methyl-2-oxopentanoic acid (0.500-20.0μg/mL), 1-linoleoyl-2-hydroxy-sn-glycero-3-phosphocholine (2.50-100μg/mL), oleic acid (10.0-400μg/mL), pantothenic acid (0.0100-0.800μg/mL), and serine (2.50-100μg/mL). Liquid chromatography was carried out on a reversed phase column with a run time of 3.1min and the mass spectrometer operated in negative MRM mode. Method validation was performed on three identical LC-MS/MS systems with five runs each. Sufficient linearity (R2>0.99) was observed for all the analytes over the ranges. The imprecision (CVs) was found to be less than 5.5% for intra-run and less than 5.8% for inter-run for the seven analytes. The analytical recovery was determined to be between 96.3 and 103% for the seven analytes. This fast and robust method has subsequently been used for patient sample analysis for the assessment of IR and IGT.

Metabolomic Profiling of the Malaria Box Reveals Antimalarial Target Pathways

The threat of widespread drug resistance to frontline antimalarials has renewed the urgency for identifying inexpensive chemotherapeutic compounds that are effective against Plasmodium falciparum, the parasite species responsible for the greatest number of malaria-related deaths worldwide. To aid in the fight against malaria, a recent extensive screening campaign has generated thousands of lead compounds with low micromolar activity against blood stage parasites. A subset of these leads has been compiled by the Medicines for Malaria Venture (MMV) into a collection of structurally diverse compounds known as the MMV Malaria Box. Currently, little is known regarding the activity of these Malaria Box compounds on parasite metabolism during intraerythrocytic development, and a majority of the targets for these drugs have yet to be defined. Here we interrogated the in vitro metabolic effects of 189 drugs (including 169 of the drug-like compounds from the Malaria Box) using ultra-high-performance liquid chromatography-mass spectrometry (UHPLC-MS). The resulting metabolic fingerprints provide information on the parasite biochemical pathways affected by pharmacologic intervention and offer a critical blueprint for selecting and advancing lead compounds as next-generation antimalarial drugs. Our results reveal several major classes of metabolic disruption, which allow us to predict the mode of action (MoA) for many of the Malaria Box compounds. We anticipate that future combination therapies will be greatly informed by these results, allowing for the selection of appropriate drug combinations that simultaneously target multiple metabolic pathways, with the aim of eliminating malaria and forestalling the expansion of drug-resistant parasites in the field.

NanoLC MALDI MS/MS based quantitative metabolomics reveals the alteration of membrane biogenesis in oral cancer

We present a label-free untargeted metabolomics approach using nanoLC-MALDI MS/MS interface for the separation, identification and quantification of the metabolites from cancer biopsies.

The Protein Interaction of RNA Helicase B (RhlB) and Polynucleotide Phosphorylase (PNPase) Contributes to the Homeostatic Control of Cysteine in Escherichia coli

PNPase, one of the major enzymes with 3′ to 5′ single-stranded RNA degradation and processing activities, can interact with the RNA helicase RhlB independently of RNA degradosome formation in Escherichia coli. Here, we report that loss of interaction between RhlB and PNPase impacts cysteine homeostasis in E. coli. By random mutagenesis, we identified a mutant RhlB^P238L that loses 75% of its ability to interact with PNPase but retains normal interaction with RNase E and RNA, in addition to exhibiting normal helicase activity. Applying microarray analyses to an E. coli strain with impaired RNA degradosome formation, we investigated the biological consequences of a weakened interaction between RhlB and PNPase. We found significant increases in 11 of 14 genes involved in cysteine biosynthesis. Subsequent Northern blot analyses showed that the up-regulated transcripts were the result of stabilization of the cysB transcript encoding a transcriptional activator for the cys operons. Furthermore, Northern blots of PNPase or RhlB mutants showed that RhlB-PNPase plays both a catalytic and structural role in regulating cysB degradation. Cells expressing the RhlB^P238L mutant exhibited an increase in intracellular cysteine and an enhanced anti-oxidative response. Collectively, this study suggests a mechanism by which bacteria use the PNPase-RhlB exosome-like complex to combat oxidative stress by modulating cysB mRNA degradation.

Development, validation, and comparison of four methods to simultaneously quantify l-arginine, citrulline, and ornithine in human plasma using hydrophilic interaction liquid chromatography and electrospray tandem mass spectrometry

To understand the role of l-arginine depletion in impaired nitric oxide synthesis in disease, it is important to simultaneously quantify arginine, citrulline, and ornithine in the plasma. Because the three amino acids are endogenous analytes, true blank matrix for them is not available. It is necessary and valuable to compare the performance of different approaches due to lack of regulatory clarity for validation. A two-step sample preparation method using methanol as protein precipitation reagent was developed in this study is used for sample preparation. Because true blank matrix for endogenous analytes is not available, water as blank matrix, 1% BSA in PBS as blank matrix, surrogate analyte, and background subtraction were designed to establish successful quantification methods. Four methods to simultaneously quantify arginine, citrulline, and ornithine in human plasma using hydrophilic interaction liquid chromatography and electrospray tandem mass spectrometry were developed, validated, and compared. The developed two-step sample preparation method using methanol as protein precipitation reagent in this study needs less time and provides higher recovery comparing with other approaches. Three of the four methods, water as blank matrix, 1% BSA in PBS as blank matrix, and surrogate analyte, have been successful in fulfilling all the criteria, while background subtraction has failed. Results of the measured concentrations in 97 human plasma samples using the three methods show that the difference between any two methods or among the three methods presents 100% of samples with less than 20% for all the three amino acids and majority of them are under 10%. The developed two-step sample preparation method using methanol as protein precipitation reagent is simple and convenient. Three of the four methods are fully validated and the validation is successful. The BSA functioned effectively as a blank matrix for these three amino acids, considering cost, data quality, matrix similarity, and practicality.

Evolution of a thienopyrimidine antitubercular relying on medicinal chemistry and metabolomics insights

The metabolic instability of an antitubercular small molecule CD117 was addressed through iterative alteration of a key sulfide substituent and interrogation of the effect on growth inhibition of cultured Mycobacterium tuberculosis. This process was informed by studies of the intramycobacterial metabolism of CD117 and its inactive carboxylic acid derivative. Isoxazole 4e and thiazole 4m demonstrated significant gains in mouse liver microsomal stability with slight losses in whole-cell activity. This work illustrates the challenges of antitubercular hit evolution, requiring a balance of chemical and biological insights.

Fast sampling method for mammalian cell metabolic analyses using liquid chromatography-mass spectrometry

Metabolomics has emerged as a powerful tool for addressing biological questions. Liquid chromatography coupled with mass spectrometry (LC-MS) is widely used for metabolic characterization, including targeted and untargeted approaches. Despite recent innovations, a crucial aspect of this technique is the sample preparation for accurate data analyses. In this protocol, we present a robust and adaptable workflow for metabolic analyses of mammalian cells from adherent cell cultures, which is particularly suited for qualitative and quantitative central metabolite characterization by LC-MS. Each sample consists of 600,000 mammalian cells grown on cover glasses, allowing for fast and complete transfer of the cells for metabolite extraction or medium exchange, e.g., for labeling experiments. The sampling procedure includes a fast and efficient washing step in liquid flow in water, which reduces cross-contamination and matrix effects while minimizing perturbation of the metabolic steady state of the cells; it is followed by quenching cell metabolism. The latter is achieved by using a -20 °C cold methanol acetonitrile mixture acidified with formic acid, followed by freeze drying, metabolite extraction and LC-MS. The protocol requires 2 s for cell sampling until quenching, and the entire protocol takes a total of 1.5 h per sample when the provided nanoscale LC-MS method is applied.

Multiplexed, quantitative, and targeted metabolite profiling by LC-MS/MRM

Targeted metabolomics, which focuses on a subset of known metabolites representative of biologically relevant metabolic pathways, is a valuable tool to discover biomarkers and link disease phenotypes to underlying mechanisms or therapeutic modes of action. A key advantage of targeted metabolomics, compared to discovery metabolomics, is its immediate readiness for extracting biological information derived from known metabolites and quantitative measurements. However, simultaneously analyzing hundreds of endogenous metabolites presents a challenge due to their diverse chemical structures and properties. Here we report a method which combines different chromatographic separation conditions, optimal ionization polarities, and the most sensitive triple-quadrupole MS-based data acquisition mode, multiple reaction monitoring (MRM), to quantitatively profile 205 endogenous metabolites in 10 min.

Pyrimidine homeostasis is accomplished by directed overflow metabolism

Cellular metabolism converts available nutrients into usable energy and biomass precursors. The process is regulated to facilitate efficient nutrient use and metabolic homeostasis. Feedback inhibition of the first committed step of a pathway by its final product is a classical means of controlling biosynthesis^1–4. In a canonical example, the first committed enzyme in the pyrimidine pathway in Escherichia coli is allosterically inhibited by cytidine triphosphate^1,4,5. The physiological consequences of disrupting this regulation, however, have not been previously explored. Here we identify an alternative regulatory strategy that enables precise control of pyrimidine pathway end-product levels, even in the presence of dysregulated biosynthetic flux. The mechanism involves cooperative feedback regulation of the near-terminal pathway enzyme uridine monophosphate kinase⁶. Such feedback leads to build-up of the pathway intermediate uridine monophosphate, which is in turn degraded by a conserved phosphatase, here termed UmpH, with previously unknown physiological function^7,8. Such directed overflow metabolism allows homeostasis of uridine triphosphate and cytidine triphosphate levels at the expense of uracil excretion and slower growth during energy limitation. Disruption of the directed overflow regulatory mechanism impairs growth in pyrimidine-rich environments. Thus, pyrimidine homeostasis involves dual regulatory strategies, with classical feedback inhibition enhancing metabolic efficiency and directed overflow metabolism ensuring end-product homeostasis.

Targeted inhibition of mutant IDH2 in leukemia cells induces cellular differentiation

A number of human cancers harbor somatic point mutations in the genes encoding isocitrate dehydrogenases 1 and 2 (IDH1 and IDH2). These mutations alter residues in the enzyme active sites and confer a gain-of-function in cancer cells, resulting in the accumulation and secretion of the oncometabolite (R)-2-hydroxyglutarate (2HG). We developed a small molecule, AGI-6780, that potently and selectively inhibits the tumor-associated mutant IDH2/R140Q. A crystal structure of AGI-6780 complexed with IDH2/R140Q revealed that the inhibitor binds in an allosteric manner at the dimer interface. The results of steady-state enzymology analysis were consistent with allostery and slow-tight binding by AGI-6780. Treatment with AGI-6780 induced differentiation of TF-1 erythroleukemia and primary human acute myelogenous leukemia cells in vitro. These data provide proof-of-concept that inhibitors targeting mutant IDH2/R140Q could have potential applications as a differentiation therapy for cancer.

Addressing the current bottlenecks of metabolomics: Isotopic Ratio Outlier Analysis™, an isotopic-labeling technique for accurate biochemical profiling

Metabolomics or biochemical profiling is a fast emerging science; however, there are still many associated bottlenecks to overcome before measurements will be considered robust. Advances in MS resolution and sensitivity, ultra pressure LC-MS, ESI, and isotopic approaches such as flux analysis and stable-isotope dilution, have made it easier to quantitate biochemicals. The digitization of mass spectrometers has simplified informatic aspects. However, issues of analytical variability, ion suppression and metabolite identification still plague metabolomics investigators. These hurdles need to be overcome for accurate metabolite quantitation not only for in vitro systems, but for complex matrices such as biofluids and tissues, before it is possible to routinely identify biomarkers that are associated with the early prediction and diagnosis of diseases. In this report, we describe a novel isotopic-labeling method that uses the creation of distinct biochemical signatures to eliminate current bottlenecks and enable accurate metabolic profiling.

Prospective serial evaluation of 2-hydroxyglutarate, during treatment of newly diagnosed acute myeloid leukemia, to assess disease activity and therapeutic response

Mutations of genes encoding isocitrate dehydrogenase (IDH1 and IDH2) have been recently described in acute myeloid leukemia (AML). Serum and myeloblast samples from patients with IDH-mutant AML contain high levels of the metabolite 2-hydroxyglutarate (2-HG), a product of the altered IDH protein. In this prospective study, we sought to determine whether 2-HG can potentially serve as a noninvasive biomarker of disease burden through serial measurements in patients receiving conventional therapy for newly diagnosed AML. Our data demonstrate that serum, urine, marrow aspirate, and myeloblast 2-HG levels are significantly higher in IDH-mutant patients, with a correlation between baseline serum and urine 2-HG levels. Serum and urine 2-HG, along with IDH1/2-mutant allele burden in marrow, decreased with response to treatment. 2-HG decrease was more rapid with induction chemotherapy compared with DNA-methyltransferase inhibitor therapy. Our data suggest that serum or urine 2-HG may serve as noninvasive biomarkers of disease activity for IDH-mutant AML.

Comparison of the secondary metabolites in two scales of cephalosporin C (CPC) fermentation and two different post-treatment processes

Cephalosporin C (CPC) is the precursor of a class of antibiotics that were more effective than traditional penicillins. CPC production is performed mainly through fermentation by Acremonium chrysogenum, whose secondary metabolism was sensitive to the environmental changes. In the present work, secondary metabolites were measured by ion-pair reversed-phase liquid chromatography tandemed with hybrid quadrupole time-of-flight mass spectrometry, and the disparity of them from two scales of CPC fermentations (pilot and industrial) and also two different post-treatment processes (oxalic acid and formaldehyde added and control) were investigated. When fermentation size was enlarged from pilot scale (50 l) to industrial scale (156,000 l), the remarkable disparities of concentrations and changing trends of the secondary metabolites in A. chrysogenum were observed, which indicated that the productivity of CPC biosynthesis was higher in the large scale of fermentation. Three environmental factors were measured, and the potential reasons that might cause the differences were analyzed. In the post-treatment process after industrial fermentation, the changes of these secondary metabolites in the tank where oxalic acid and formaldehyde were added were much less than the control tank where none was added. This indicated that the quality of the final product was more stable after the oxalic acid and formaldehyde were added in the post-treatment process. These findings provided new insight into industrial CPC production.

Quantitative analysis of anthocyanins in Euterpe oleracea (açaí) dietary supplement raw materials and capsules by Q-TOF liquid chromatography/mass spectrometry

CONTEXT

Euterpe oleracea Mart. (Arecaceae) fruits and their dietary supplements are gaining much popularity internationally. Anthocyanins and their aglycons are responsible for the dense color of açaí fruit and are associated with a wide spectrum of health promoting effects.

OBJECTIVE

Quantitative analysis of anthocyanins in açaí dietary supplement raw materials; processed açaí powder (ADSR-1), organic açaí powder (ADSR-2), and nonorganic açaí powder (ADSR-3) by quadrupole-time-of-flight liquid chromatography/mass spectrometry (Q-TOF LC/MS) have been reported in this study.

MATERIALS AND METHODS

The chromatographic separation for anthocyanins was achieved using a C-18 column with a gradient of 0.1% formic acid in water and 0.1% formic acid in methanol and acetonitrile (50:50, v/v). MS and MS/MS experiments were carried out on an electrospray ionization-Q-TOF LC/MS.

RESULTS

Except for ASDR-2, all the açaí samples were found to have cyanidin 3-glucoside (1), cyanidin 3-sambubioside (2), cyanidin 3-rutinoside (3), and peonidin 3-rutinoside (4). ASDR-2 contained anthocyanins 1 and 3. Among the açaí samples quantified, ADSR-3 showed higher concentration of anthocyanins compared to other raw materials and capsules tested in this study.

DISCUSSION AND CONCLUSION

The anthocyanins 1-4 present in ADSR-3 were 27.13 ± 0.37, 1.76 ± 0.04, 31.07 ± 0.49, and 3.46 ± 0.08 mg/100 g dry wt, respectively. The LOQ values for anthocyanins 1-4 were in the range of 2.44-9.76 ng/mL. Accuracy of the method was assessed by performing a recovery experiments. The intraday and interday variations (RSDs) were <10%. This is the first report on quantitation of anthocyanins in açaí dietary supplement raw materials and capsules.