Oxidative Decomposition of Vitamin C in Drinking Water

Open port sampling interface mass spectrometry of wipe-based explosives, oxidizers, and narcotics for trace contraband detection

Rapid screening for chemical traces of explosives and narcotics is widely used to support homeland security and law enforcement. These target compounds span a range of physicochemical properties from organic to inorganic, with preferential ionization pathways in both negative and positive mode operation. Nonvolatile inorganic oxidizers present in homemade fuel-oxidizer mixtures, pyrotechnics, and propellants create a unique challenge to traditional thermal desorption-based technologies. Developments in solid-liquid extraction techniques, specifically, open port sampling interface mass spectrometry (OPSI-MS) provide compelling capabilities to address these hurdles. In this proof of concept study, we investigated the trace detection of wipe-based (i.e., common swipe sampling collection method) explosives, oxidizers, and narcotics using an OPSI source and compact single quadrupole mass analyzer. The liquid dissolution and extraction capabilities of OPSI enabled detection of both traditional military-grade explosives and homemade explosive oxidizers. OPSI-MS sensitivities to a series of seven target compounds from polytetrafluoroethylene (PTFE) coated fiberglass sampling wipes were on the order of several nanograms to sub-nanogram levels. Comparisons with direct solution-based sample analysis enabled quantification of wipe-based sample extraction effects. The system demonstrated quick temporal responses, polarity switching capabilities, and rapid signal decay with minimal carryover, all critical to high throughput screening applications. Coupling traditional swipe sampling with OPSI-MS offers a promising tool for contraband screening applications.

DART-MS Spectral Similarity of Infrared Thermally Desorbed Solid Particulate and Solution Cast Propellant Samples

Security and forensic applications employ test and reference materials to develop, calibrate, and validate analytical instrumentation such as mass spectrometry for the trace detection and chemical analysis of target analytes. An emerging class of target analytes includes homemade fuel oxidizer explosives based on pyrotechnics, propellants, and powder mixtures. Test materials for these compounds must appropriately and accurately embody the physical and chemical nature of the threat. Precision liquid deposition methods have long been employed for creation of trace level test materials. Mass spectral similarity and chemical signature differences between solid particulate and solution cast (i.e., liquid deposited) propellant samples were investigated by infrared thermal desorption direct analysis in real time mass spectrometry (IRTD-DART-MS). Differences in the mass spectra and ion distributions of solid and liquid deposited black powders and black powder substitutes were observed. These differences were attributed to chemical processes (e.g., degradation) and physical differences in the crystal formation, spatial distribution, morphology, and size. The production and deposition of test and reference materials remain critical to developing new technologies and detecting evolving threats.

Vitamin C supplementation is necessary for patients with coronavirus disease: An ultra-high-performance liquid chromatography-tandem mass spectrometry finding

To administer vitamin C (VC) with precision to patients with the coronavirus disease (COVID-19), we developed an ultra-high-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) method to assess plasma VC concentrations. 31 patients with COVID-19 and 51 healthy volunteers were enrolled. VC stability was evaluated in blood, plasma, and precipitant-containing stabilizers. A proportion of 7.7 % of VC was degraded in blood at room temperature (RT) (approximately 20–25 °C) at 1.5 h post administration with respect to the proportion degraded at 0.5 h, but without statistical difference. VC was stable in plasma for 0.75 h at RT, 2 h at 4 °C, 5 days at −40 °C, and 4 h in precipitant-containing stabilizer (2 % oxalic acid) at RT. The mean plasma concentration of VC in patients with COVID-19 was 2.00 mg/L (0.5–4.90) (n = 8), which was almost 5-fold lower than that in healthy volunteers (9.23 mg/L (3.09. 35.30)) (n = 51). After high-dose VC treatment, the mean VC concentration increased to 13.46 mg/L (3.93. 34.70) (n = 36), higher than that in healthy volunteers, and was within the normal range (6–20 mg/L). In summary, we developed a simple UPLC-MS/MS method to quantify VC in plasma, and determined the duration for which the sample remained stable. VC levels in patients with COVID-19 were considerably low, and supplementation at 100 mg/kg/day is considered highly essential.

1H-NMR-based urinary metabolomic analysis for the preventive effects of gushudan on glucocorticoid-induced osteoporosis rats

Gushudan (GSD), a traditional Chinese medicine with a history of more than 15 years, has been shown to have anti-osteoporosis effects, but the specific therapeutic mechanism behind it is still unclear. To further elucidate the pathogenesis of osteoporosis and the preventive mechanism of GSD on glucocorticoid-induced osteoporosis (GIOP) rats, a rapid and comprehensive ¹H NMR metabolomics method was established to detect urinary metabolic profiles in the control group, model group and GSD treatment group in this study. The orthogonal partial least squares discriminant analysis (OPLS-DA) was performed to investigate changes in the metabolites, and related metabolic pathways were discovered using MetaboAnalyst platform. As a result, a total of 27 differential metabolites were identified. Of these, 17 metabolites such as formate, allantoin and l-threonate were newly discovered as GIOP potential biomarkers. Energy metabolism, intestinal flora metabolism, amino acid metabolism and oxidative stress response were significantly changed in the urinary profiles of GIOP rats, and GSD could play an anti-osteoporosis role by regulating these metabolic pathways. This study compliments the earlier LC-MS based urine metabolomics research, and helps further understand the pathogenesis of osteoporosis and the potential preventive effects of GSD on GIOP rats.

Plasma metabolomic fingerprint of advanced cirrhosis stages among HIV/HCV-coinfected and HCV-monoinfected patients

BACKGROUND & AIMS

Hepatitis C virus (HCV), human immunodeficiency virus (HIV) and cirrhosis induce metabolic disorders. Here, we aimed to evaluate the association of plasma metabolites with Child-Turcotte-Pugh (CTP) score and hepatic decompensation in HIV/HCV-coinfected and HCV-monoinfected patients with advanced cirrhosis.

METHODS

A cross-sectional study was carried out in 62 HIV/HCV-coinfected and 28 HCV-monoinfected patients. Metabolomics analysis was performed by gas chromatography-mass spectrometry (GC-MS) and liquid chromatography-mass spectrometry (LC-MS). The statistical association analysis was performed by partial least squares discriminant analysis (PLS-DA) and generalized linear model (GLM) with binomial distribution (to analyse HIV coinfection, high alcohol intake, treatment with statins, previous HCV therapy failure and decompensation) and ordinal logistic regression (OLR) models to analyse different stages of cirrhosis (CTP score).

RESULTS

The statistical analysis identified plasma metabolites associated with HIV coinfection, high alcohol intake, CTP score and hepatic decompensation. Overall, fatty acids, bile acids, aromatic and sulphur amino acids, butyrate derivatives, oxidized phospholipids, energy-related metabolites and bacterial fermentation-related metabolites were increased in more advanced cirrhosis stages; while lysophosphatidylcholines and lysophosphatidylethanolamines, branched-chain amino acids (BCAA) and metabolites of tricarboxylic acid cycle, among others, were decreased in more advanced cirrhosis. Most of the significant metabolites displayed a similar trend after stratifying for HIV/HCV- and HCV-infected patients. Glycolic acid, LPC (16:0) and taurocholic acid had high accuracy for discriminating patients according to decompensated cirrhosis (CTP ≥ 7).

CONCLUSION

Altered plasma metabolomic profile was associated with advanced stages of cirrhosis in HIV/HCV-coinfected and HCV-monoinfected patients.

Investigating the Interaction of Ascorbic Acid with Anthocyanins and Pyranoanthocyanins

Juices colored by anthocyanins experience color loss related to fortification with ascorbic acid (AA), thought to be the result of condensation at Carbon-4 of anthocyanins. To further understand this mechanism, pyranoanthocyanins, having a fourth-ring covalently occupying Carbon-4, were synthesized to compare its reactivity with AA against that of anthocyanins. Pyranoanthocyanins were synthesized by combining chokeberry anthocyanins with pyruvic acid. AA (250–1000 mg/L) was added to either chokeberry extract, cyanidin-3-galactoside, or 5-Carboxypyranocyanidin-3-galactoside. Samples were stored in the dark for 5 days at 25 °C and spectra (380–700 nm), color (CIE-L*c*h*), and composition changes (HPLC-MS/MS) were monitored. Extensive bleaching occurred for cyanidin-3-galactoside and chokeberry colored solutions, with a decrease in half-lives from 22.8 to 0.3 days for Cyanidin-3-galactoside when 1000 mg/L AA was added. 5-Carboxypyranocyanidin-3-galactoside solution better maintained color with limited loss in absorbance, due to the formation of colored degradation products (λ_vis-max = 477 to 487 nm), and half-life decrease from 40.8 to 2.7 days, an 8–13-fold improvement compared to anthocyanins. This suggested alternative sites of reactivity with AA. Carbon-4 may be the preferred site for AA-pigment interactions, but it was not the only location. With Carbon-4 blocked, 5-Carboxypyranocyanidin-3-galactoside reacted with AA to form new pigments and reduce bleaching.

Defective methionine metabolism in the brain after repeated blast exposures might contribute to increased oxidative stress

Blast-induced traumatic brain injury (bTBI) is one of the major disabilities in Service Members returning from recent military operations. The neurobiological underpinnings of bTBI, which are associated with acute and chronic neuropathological and neurobehavioral deficits, are uncertain. Increased oxidative stress in the brain is reported to play a significant role promoting neuronal damage associated with both brain injury and neurodegenerative disorders. In this study, brains of rats exposed to repeated blasts in a shock tube underwent untargeted profiling of primary metabolism by automatic linear exchange/cold injection GC-TOF mass spectrometry and revealed acute and sub-acute disruptions in the metabolism of the essential amino acid methionine and associated antioxidants. Methionine sulfoxide, the oxidized metabolite of methionine, showed a sustained increase in the brain after blast exposure which was associated with a significant decrease in cysteine, the amino acid derived from methionine. Glutathione, the antioxidant synthesized from cysteine, also concomitantly decreased as did the antioxidant ascorbic acid. Reductions in ascorbic acid were accompanied by increased levels of its oxidized metabolite, dehydroascorbic acid and other metabolites such as threonic acid, isothreonic acid, glycolic acid and oxalic acid. Fluorometric analysis of the brains showed acute and sub-acute increase in total reactive oxygen species. In view of the fundamental importance of glutathione in the brain as an antioxidant, including its role in the reduction of dehydroascorbic acid to ascorbic acid, the disruptions in methionine metabolism elicited by blast exposure might prominently contribute to neuronal injury by promoting increased and sustained oxidative stress.

Metabolomics to Detect Response of Lettuce (Lactuca sativa) to Cu(OH)2 Nanopesticides: Oxidative Stress Response and Detoxification Mechanisms

There has been an increasing influx of nanopesticides into agriculture in recent years. Understanding the interaction between nanopesticides and edible plants is crucial in evaluating the potential impact of nanotechnology on the environment and agriculture. Here we exposed lettuce plants to Cu(OH)2 nanopesticides (1050-2100 mg/L) through foliar spray for one month. Inductively coupled plasma-mass spectrometry (ICP-MS) results indicate that 97-99% (1353-2501 mg/kg) of copper was sequestered in the leaves and only a small percentage (1-3%) (17.5-56.9 mg/kg) was translocated to root tissues through phloem loading. Gas chromatography-time-of-flight mass spectrometry (GC-TOF-MS) based metabolomics combined with partial least squares-discriminant analysis (PLS-DA) multivariate analysis revealed that Cu(OH)2 nanopesticides altered metabolite levels of lettuce leaves. Tricarboxylic (TCA) cycle and a number of amino acid-related biological pathways were disturbed. Some antioxidant levels (cis-caffeic acid, chlorogenic acid, 3,4-dihydroxycinnamic acid, dehydroascorbic acid) were significantly decreased compared to the control, indicating that oxidative stress and a defense response occurred. Nicotianamine, a copper chelator, increased by 12-27 fold compared to the control, which may represent a detoxification mechanism. The up-regulation of polyamines (spermidine and putrescine) and potassium may mitigate oxidative stress and enhance tolerance. The data presented here provide a molecular-scale perspective on the response of plants to copper nanopesticides.

Ascorbic acid intake and oxalate synthesis

In humans, approximately 60 mg of ascorbic acid (AA) breaks down in the body each day and has to be replaced by a dietary intake of 70 mg in women and 90 mg in men to maintain optimal health and AA homeostasis. The breakdown of AA is non-enzymatic and results in oxalate formation. The exact amount of oxalate formed has been difficult to ascertain primarily due to the limited availability of healthy human tissue for such research and the difficulty in measuring AA and its breakdown products. The breakdown of 60 mg of AA to oxalate could potentially result in the formation of up to 30 mg oxalate per day. This exceeds our estimates of the endogenous production of 10-25 mg oxalate per day, indicating that degradative pathways that do not form oxalate exist. In this review, we examine what is known about the pathways of AA metabolism and how oxalate forms. We further identify how gaps in our knowledge may be filled to more precisely determine the contribution of AA breakdown to oxalate production in humans. The use of stable isotopes of AA to directly assess the conversion of vitamin to oxalate should help fill this void.

Dual release of a hydrophilic and a hydrophobic osteogenic factor from a single liposome

Dual release of growth/differentiation factors from liposomes induced osteogenic differentiation of mesenchymal stem cells.

Analysis of ascorbic acid based black powder substitutes by high-performance liquid chromatography/electrospray ionization quadrupole time-of-flight mass spectrometry

Black powder substitutes are an important sub-group of explosive propellants in the United States because they are readily accessible, and can be used as fillers for improvised explosive devices. Many brands of black powder substitutes incorporate an ascorbic acid fuel source with potassium nitrate (KNO(3)) and/or potassium perchlorate (KClO(4)) oxidizer(s). A gradient high-performance liquid chromatography/electrospray ionization quadrupole time-of-flight mass spectrometry (HPLC/ESI-QToFMS) method has been developed for the analysis of both the organic and the inorganic constituents. The HPLC/ESI-QToFMS method was utilized to examine aqueous extracts of intact samples and post-burn residues from six different brands of ascorbic acid based powders. Aqueous extracts of the post-blast residues from two brands of ascorbic acid based propellant were also analyzed. The results showed that both the ascorbic acid fuel and the inorganic oxidizer(s) KClO(4) and/or KNO(3) were successfully detected via the [M-H](-) ion of ascorbic acid and the anions (ClO(4) (-) and NO(3) (-)) of the oxidizers. This method was proven to be a rapid and efficient procedure for the analysis of this class of explosives. The high mass resolution provided by the QToFMS instrument fulfills the degree of certainty required in a court of law.

Effects of iron on Vitamin C/copper-induced hydroxyl radical generation in bicarbonate-rich water

The aim of this study was to evaluate whether iron, like copper, could support Vitamin C mediated hydroxyl radical formation in bicarbonate-rich water. By using the hydroxyl radical indicator coumarin-3-carboxylic acid, we found that iron, in contrast to copper, was not capable to support Vitamin C induced hydroxyl radical formation. However, when 0.2 mg/l iron and 0.1 mg/l copper were both added to bicarbonate supplemented Milli-Q water, the Vitamin C induced formation of 7-hydroxycoumarin, as measured by HPLC analysis, was inhibited by 47.5%. The inhibition of hydroxyl radical formation by iron was also evident in the experiments performed on copper contaminated bicarbonate-rich household drinking water samples. In the presence of 0.2 mg/l of ferric iron the ascorbic acid induced hydroxyl radical formation was inhibited by 36.0-44.6%. This inhibition was even more significant, 47.0-59.2%, when 0.8 mg/l of ferric iron was present. None of the other redox-active metals, e.g. manganese, nickel or cobalt, could support ascorbic acid induced hydroxyl radical formation and did not have any impact on the ascorbic acid/copper-induced hydroxyl radical generation. Our results show, that iron cannot by itself produce hydroxyl radicals in bicarbonate rich water but can significantly reduce Vitamin C/copper-induced hydroxyl radical formation. These findings might partly explain the mechanism for the iron-induced protective effect on various copper related degenerative disorders that earlier has been observed in animal model systems.

Reduction of dehydroascorbic acid at low pH

Ascorbic acid and dehydroascorbic acid are unstable in aqueous solution in the presence of copper and iron ions, causing problems in the routine analysis of vitamin C. Their stability can be improved by lowering the pH below 2, preferably with metaphosphoric acid. Dehydroascorbic acid, an oxidised form of vitamin C, gives a relatively low response on the majority of chromatographic detectors, and is therefore routinely determined as the increase of ascorbic acid formed after reduction. The reduction step is routinely performed at a pH that is suboptimal for the stability of both forms. In this paper, the reduction of dehydroascorbic acid with tris-[2-carboxyethyl] phosphine (TCEP) at pH below 2 is evaluated. Dehydroascorbic acid is fully reduced with TCEP in metaphosphoric acid in less than 20 min, and yields of ascorbic acid are the same as at higher pH. TCEP and ascorbic acid formed by reduction, are more stable in metaphosphoric acid than in acetate or citrate buffers at pH 5, in the presence of redox active copper ions. The simple experimental procedure and low probability of artefacts are major benefits of this method, over those currently applied in a routine assay of vitamin C, performed on large number of samples.

Iron prevents ascorbic acid (vitamin C) induced hydrogen peroxide accumulation in copper contaminated drinking water

Ascorbic acid (vitamin C) induced hydrogen peroxide (H(2)O(2)) formation was measured in household drinking water and metal supplemented Milli-Q water by using the FOX assay. Here we show that ascorbic acid readily induces H(2)O(2) formation in Cu(II) supplemented Milli-Q water and poorly buffered household drinking water. In contrast to Cu(II), iron was not capable to support ascorbic acid induced H(2)O(2) formation during acidic conditions (pH: 3.5-5). In 12 out of the 48 drinking water samples incubated with 2 mM ascorbic acid, the H(2)O(2) concentration exceeded 400 microM. However, when trace amounts of Fe(III) (0.2 mg/l) was present during incubation, the ascorbic acid/Cu(II)-induced H(2)O(2) accumulation was totally blocked. Of the other common divalent or trivalent metal ions tested, that are normally present in drinking water (calcium, magnesium, zinc, cobalt, manganese or aluminum), only calcium and magnesium displayed a modest inhibitory activity on the ascorbic acid/Cu(II)-induced H(2)O(2) formation. Oxalic acid, one of the degradation products from ascorbic acid, was confirmed to actively participate in the iron induced degradation of H(2)O(2). Ascorbic acid/Cu(II)-induced H(2)O(2) formation during acidic conditions, as demonstrated here in poorly buffered drinking water, could be of importance in host defense against bacterial infections. In addition, our findings might explain the mechanism for the protective effect of iron against vitamin C induced cell toxicity.