Determination of organic acids in Vaccinium berry standard reference materials

Gas chromatography-mass spectrometric determination of organic acids by ion pair liquid extraction followed by in-situ butylation from aqua feed samples

A rapid and sensitive analytical method was developed to quantitatively determine organic acids (OAs) from fish feed samples extracted by ion-pair (IP) solvent extraction, followed by in-situ butylation and gas chromatography-mass spectrometric (GC-MS) analysis. The extraction of OAs was carried out with acetonitrile containing 10 mM tetrabutylammonium hydroxide (TBAH), and the analytes were derivatized to their butyl esters in the injection port of the GC-MS system. The developed method was validated in the range of 1-5000 ng/g, with recoveries ranging from 93-117%. The limit of detection (LOD) and limit of quantification (LOQ) of the method was 1-5 ng/g and 2-10 ng/g, respectively, yielding good linearity (R² > 0.9990) and precision with a relative standard deviation less than 10%. The proposed method was successfully applied to analyze OAs in sinking and floating fish feed samples. The analyzed samples showed the presence of benzoic, succinic, fumaric, glutaric, adipic, and phthalic acids in sinking feed samples; and benzoic, succinic, adipic, phthalic acids in floating feed samples, respectively.

Comparison of chemometric strategies for potential exposure marker discovery and false-positive reduction in untargeted metabolomics: application to the serum analysis by LC-HRMS after intake of Vaccinium fruit supplements

Untargeted liquid chromatographic-high-resolution mass spectrometric (LC-HRMS) metabolomics for potential exposure marker (PEM) discovery in nutrikinetic studies generates complex outputs. The correct selection of statistically significant PEMs is a crucial analytical step for understanding nutrition-health interactions. Hence, in this paper, different chemometric selection workflows for PEM discovery, using multivariate or univariate parametric or non-parametric data analyses, were comparatively tested and evaluated. The PEM selection protocols were applied to a small-sample-size untargeted LC-HRMS study of a longitudinal set of serum samples from 20 volunteers after a single intake of (poly)phenolic-rich Vaccinium myrtillus and Vaccinium corymbosum supplements. The non-parametric Games-Howell test identified a restricted group of significant features, thus minimizing the risk of false-positive retention. Among the forty-seven PEMs exhibiting a statistically significant postprandial kinetics, twelve were successfully annotated as purine pathway metabolites, benzoic and benzodiol metabolites, indole alkaloids, and organic and fatty acids, and five (i.e. octahydro-methyl-β-carboline-dicarboxylic acid, tetrahydro-methyl-β-carboline-dicarboxylic acid, citric acid, caprylic acid, and azelaic acid) were associated to Vaccinium berry consumption for the first time. The analysis of the area under the curve of the longitudinal dataset highlighted thirteen statistically significant PEMs discriminating the two interventions, including four intra-intervention relevant metabolites (i.e. abscisic acid glucuronide, catechol sulphate, methyl-catechol sulphate, and α-hydroxy-hippuric acid). Principal component analysis and sample classification through linear discriminant analysis performed on PEM maximum intensity confirmed the discriminating role of these PEMs.

Pharmacokinetics of Shikimic Acid Following Intragastric and Intravenous Administrations in Rats

Shikimic acid, a critical starting material for the semi-total synthesis of oseltamivir to treat and prevent influenza, exerts many pharmacological effects. However, the optimal bioanalytical method has not been adequately defined. We used liquid chromatography-tandem mass spectrometry to quantitate shikimic acid in rat plasma and studied its pharmacokinetics after intragastric and intravenous administration. Plasma was spiked with an internal standard, and the proteins were precipitated with acetonitrile, followed by solvent evaporation and reconstitution of the mobile phase. Shikimic acid was separated on a hydrophilic reverse-phase column and showed a mass transition ([M-H]⁻) at m/z 173.4→136.6. Shikimic acid exhibited bi-exponential decay after intravenous dosing, with a rapid distribution (5.57 h⁻¹) up to 1 h followed by slow elimination (0.78 h⁻¹). The steady state distribution and clearance volumes were 5.17 and 1.79 L/h/kg, respectively. After intragastric administration, the shikimic acid level peaked at about 3 h, and the material then disappeared mono-exponentially with a half-life of 1.3 h. A double peak phenomenon was observed. The absolute oral bioavailability was about 10% in rats. We explored the relationship between the pharmacokinetics and pharmacodynamics of shikimic acid.

Ion Chromatography and Related Techniques in Carboxylic Acids Analysis

Ion chromatography (IC) is a variant of high-performance liquid chromatography. Its most important applications include the determination of inorganic and some organic ions in different types of liquid samples. The development of new types of stationary phases with various separation mechanisms, sample preparation methods, and detection modes has extended ion chromatography applications to practically all ionic and ionogenic substances, as well as extending sample types to include gaseous and solid matrices. Carboxylic acids and their derivatives are examples of compounds that are becoming more frequently analyzed using ion chromatography and related techniques. Their occurrence in the environment can be natural or anthropogenic in origin and are broadly used in various industries and daily life. This article discusses the applications of ion chromatography and related techniques for the determination of carboxylic acids in different types of liquid, solid, and gaseous matrices. It also presents detailed methodologies and literature data on this subject from the last 15 years.

Evolution of reference materials for the determination of organic nutrients in food and dietary supplements-a critical review

For over 40 years, food-matrix certified reference materials (CRMs) have been available for determination of trace element content, and a wide variety of materials are available from most producers of CRMs. However, the availability of food-matrix CRMs for organic nutrients has been more limited. The European Commission (EC) Bureau Communautaire de Référence (BCR) and the National Institute of Standards and Technology (NIST) introduced food-matrix CRMs with values assigned for vitamins and other organic nutrients such as fatty acids and carotenoids in the 1990s. The number of organic nutrients for which values were assigned has increased significantly in the past decade, and the approach and analytical methods used for assignment of the certified values have also evolved. Recently, dietary supplement-matrix CRMs such as multivitamin tablets with values assigned for vitamins and carotenoids, and fish and plant oils with values assigned for fatty acids have appeared. The development, evolution, and improvement of food- and dietary supplement-matrix CRMs for determination of vitamins, carotenoids, and fatty acids are described, with emphasis on CRMs made available in the past 10 years. Recent food and dietary supplement CRMs for the determination of organic nutrients include infant formula, multivitamin tablets, milk and egg powders, breakfast cereal, meat homogenate, blueberries, soy flour, fish and plant oils, dry cat food, and protein drink powder. Many of these food- and supplement-matrix CRMs have values assigned for over 80 organic and inorganic nutrients, toxic elements, proximates, and contaminants. The review provides a critical assessment of the challenges and evolving improvements in the production and the analytical methods used for value assignment of these CRMs. The current status and future needs for additional food- and dietary supplement-matrix CRMs for organic nutrients are also discussed. Graphical abstract Food Composition Triangle with currently-available food-matrix certified reference materials (CRMs) for the determination of organic nutrients positioned according to fat, protein, and carbohydrate composition.

Chemical profile and antioxidant potential of four table grape (Vitis vinifera) cultivars grown in Douro region, Portugal

The aim of this work was to improve the knowledge about the potential of Douro region (North of Portugal) to produce table grapes of superior quality. Skin, pulp, and seeds of four table grapes ‘Alphonse Lavallée’, ‘Cardinal’, ‘Dona Maria’ and ‘Muscat Hamburgo’ produced in Dour region, collected at commercial maturity stage, were evaluated. Phenolic compounds, organic acids and sugars were determined in each cultivar and in the different parts of the grape by HPLC-DAD, while the antioxidant properties were evaluated by DPPH, Cuprac and lipid peroxidation assays. Phenolics from different classes were found: four anthocyanins (delphynidin, cyanidin, petunidin and malvidin), two hydroxibenzoic acids (gallic acid and protocatechuic acid), three hydroxycinnamic acids (caffeic, chlorogenic and coumaric acids), one flavonol (rutin), three flavan-3-ols ((+)-catechin, (-)-epicatechin, and (-)-epicagallocatechin)), one oligomer (procyanidin B2) and one stilbene (resveratrol). In addition, three organic acids (tartaric, malic and citric acids) and two types of sugars (glucose and fructose) were detected in all samples. Differences were found between cultivars (p<0.001) and sample material type (p<0.001). Skins presented the higher content in anthocyanins, seeds in flavan-3-ols and pulps in phenolic acids, organic acids and free-sugars. The cultivar ‘Cardinal’ showed the highest content in phytochemicals, while ‘Dona Maria’ was the cultivar with the lowest content. Nonetheless, the content of flavan-3-ols and organic acids in ‘Dona Maria’, associated with its higher antioxidant capacity, makes it an interesting choice as table grape from healthier point of view. According to our results, Douro region have proper environmental conditions to produce these table grapes.

Method development for the certification of a ginsenoside calibration solution via liquid chromatography with absorbance and mass spectrometric detection

The research presented here describes the development of two analytical methods for use in the certification of a ginsenoside calibration solution Standard Reference Material (SRM) 3389 consisting of seven ginsenosides: Rg1, Re, Rf, Rb1, Rc, Rb2, and Rd. The new methods utilized the liquid chromatographic (LC) separation of ginsenoside mixtures with absorbance detection (UV) and mass spectrometry (MS). Ginsenosides Rb3, Rg2, Rg3, Rh1, and Rh2 were evaluated for use as internal standards for LC/MS measurements. The 12 ginsenosides were baseline resolved by gradient elution LC/UV, with an initial mobile phase composition of 22% acetonitrile and 78% water, flow rate of 0.7 mL/min, and column temperature of 25 °C. The work presented here includes a detailed investigation into the optimization of the chromatographic conditions to minimize measurement biases that result from unresolved constituents. Temperature and mobile phase composition are known to play a significant role in column selectivity; however, flow rate is expected to influence primarily the separation efficiency and detection sensitivity. In the current study, column selectivity changed with changes in flow rate and the relative retention of ginsenoside Rg2 and Rh1 changed as the flow rate increased from 0.6 mL/min to 1.0 mL/min.

Anti-proliferative properties of commercial Pelargonium sidoides tincture, with cell-cycle G0/G1 arrest and apoptosis in Jurkat leukaemia cells

Context Pelargonium sidoides DC (Geraniaceae) is an important medicinal plant indigenous to South Africa and Lesotho. Previous studies have shown that root extracts are rich in polyphenolic compounds with antibacterial, antiviral and immunomodulatory activities. Little is known regarding the anticancer properties of Pelargonium sidoides extracts. Objective This study evaluates the anti-proliferative effects of a Pelargonium sidoides radix mother tincture (PST). Materials and methods The PST was characterized by LC-MS/MS. Anti-proliferative activity was evaluated in the pre-screen panel of the National Cancer Institute (NCI-H460, MCF-7 and SF-268) and the Jurkat leukaemia cell line at concentrations of 0-150 μg/mL. The effect on cell growth was determined with sulphorhodamine B and 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assays after 72 h. The effect on cell cycle and apoptosis induction in Jurkat cells was determined by flow cytometry with propidium iodide and Annexin V: fluorescein isothiocyanate staining. Results Dihydroxycoumarin sulphates, gallic acid as well as gallocatechin dimers and trimers were characterized in PST by mass spectrometry. Moderate anti-proliferative effects with GI50 values between 40 and 80 μg/mL were observed in the NCI-pre-screen panel. Strong activity observed with Jurkat cells with a GI50 value of 6.2 μg/mL, significantly better than positive control 5-fluorouracil (GI50 value of 9.7 μg/mL). The PST arrested Jurkat cells at the G0/G1 phase of the cell cycle and increased the apoptotic cells from 9% to 21%, while the dead cells increased from 4% to 17%. Conclusion We present evidence that P. sidoides has cancer cell type-specific anti-proliferative effects and may be a source of novel anticancer molecules.

White versus blue: Does the wild 'albino' bilberry (Vaccinium myrtillus L.) differ in fruit quality compared to the blue one?

Wild albino and blue bilberry fruit were analyzed to compare different fruit characteristics linked to the composition of primary and secondary metabolites. Compounds were identified using HPLC-MS and standard quality parameters were determined. Albino berries were significantly smaller, accumulated less water and were characterized by 23% higher dry weight. Soluble solids content and pH value were higher in albino bilberry and their surface was lighter and characterized by a yellow hue. Both bilberry forms accumulated identical individual sugars and organic acids; however, the albino form had 33% higher content of total sugars and 9% higher content of total organic acids compared to the blue type. Fifteen anthocyanins were identified in both forms, but in albino bilberries, individual anthocyanins were only detected in traces. Blue bilberry contained 1.6-fold higher levels of flavanols, 2.1-fold higher levels of flavonols, 2.5-fold higher levels of hydroxycinnamic acid derivatives and consequently, 4.6-fold higher total phenolic content.

Effect of Harvest Year and Altitude on Nutritional and Biometric Characteristics of Blueberry Cultivars

In recent years the consumption of small fruits has increased continuously and knowledge about the more suitable production requirements is essential. This study aims to evaluate the influence of harvest year and altitude on chemical composition of four blueberry cultivars, in order to create rentable opportunities for producers and minimize eventual losses in quality fruits. Dry mass, protein, fat, energy, free sugars, organic acids, and vitamin C contents were determined using HPLC-UV-DAD and spectrophotometric methods. Differences (p<0.05) in the concentrations of free sugars, organic acids, and vitamin C were found among years, while the altitude had no (p>0.05) influence. Citric acid was the main organic acid and fructose the most abundant sugar in blueberries. Fruits of “Ozarkblue” had the highest mass and volume whilst the “Bluecrop” was the cultivar with highest crude protein and fat contents. “Goldtraube” showed the highest content of sucrose and organic acids and “Duke” had the highest content of fructose.

A comparison of fruit quality parameters of wild bilberry (Vaccinium myrtillus L.) growing at different locations

BACKGROUND

As a part of the ongoing interest in nutritional and nutraceutical properties of locally produced fruits, the aim of the article was to determine sugars, organic acids, polyphenols and antioxidant capacity of wild bilberries grown in Slovenia. Primary and secondary metabolite composition of bilberry fruit was compared among six phyto-climatic conditions, differing in photosynthetic active radiation and light intensity.

RESULTS

Three sugars were quantified in bilberry fruit, the predominant being fructose and glucose, along with five organic acids. Bilberry fruit contained high levels of anthocyanins (cyanidin, delphinidin, malvidin, petunidin and peonidin glycosides), hydroxycinnamic acid derivatives and low levels of flavonol glycosides (mainly quercetin and myricetin glycosides), flavan-3-ols, proanthocyanidins and iridoids. The results of the study indicate that bilberries growing in sites with high photosynthetic active radiation (PAR) contained higher levels of total sugars, anthocyanins, flavonols and hydroxycinnamic acids and lower levels of organic acids compared with bilberry fruit from low-light locations. Consequently, total phenolic content and antioxidative capacity of the fruit from high-PAR locations were significantly increased.

CONCLUSION

Bilberries from different natural habitats differ significantly in the quantity of sugars, organic acids and phenolic compounds. Our results contribute to a fuller understanding of the relationships between environmental factors and accumulation of primary and secondary metabolites in bilberry fruits.

Simultaneous separation and determination of organic acids in blueberry juices by capillary electrophoresis- electrospray ionization mass spectrometry

A sensitive and expeditious capillary electrophoresis-electrospray ionization mass spectrometry(CE-ESIMS) method for the separation, identification and determination of succinic, citric, salicylic, malic, benzoic, sorbic, ascorbic, and tartaric acid in blueberry juices has been developed. In order to obtain the analytical separation, CE-MS interface parameters(e.g., buffer pH and composition, sheath liquid and gas flow rates, sheath liquid composition, electrospray voltage, etc.) were carefully optimized. Eight organic acids were baseline separated in 8 min under optimum experimental conditions. The precisions for eight replicate separations of a standard mixture solution were 2.54-4.12 % for peak area and 0.85-2.12 % for migration time respectively. The linear ranges were 10.0-1000.0, 8.0-1000.0, 13.0-1000.0, 6.0-1000.0, 9.0-1000.0, 3.2-600.0, 6.0-1000.0 and 18.0-1000.0 μg/L for succinic, citric, salicylic, malic, benzoic, sorbic, ascorbic, and tartaric acid with detection limits of 2.5, 2.0, 3.4, 1.5, 2.2, 0.8, 1.5, 4.5 μg/L, respectively. The average recoveries of the eight components were between 86.8 and 99.8 % with RSDs of 1.8-5.3 %. The proposed method was applied to the simultaneous analysis of eight analytes in Blueberry Juice samples with satisfactory results.

Metabolomic analysis of key central carbon metabolism carboxylic acids as their 3-nitrophenylhydrazones by UPLC/ESI-MS

Multiple hydroxy-, keto-, di-, and tri-carboxylic acids are among the cellular metabolites of central carbon metabolism (CCM). Sensitive and reliable analysis of these carboxylates is important for many biological and cell engineering studies. In this work, we examined 3-nitrophenylhydrazine as a derivatizing reagent and optimized the reaction conditions for the measurement of ten CCM-related carboxylic compounds, including glycolate, lactate, malate, fumarate, succinate, citrate, isocitrate, pyruvate, oxaloacetate, and α-ketoglutarate as their 3-nitrophenylhydrazones using LC/MS with ESI. With the derivatization protocol which we have developed, and using negative-ion multiple-reaction monitoring on a triple-quadrupole instrument, all of the carboxylates showed good linearity within a dynamic range of ca. 200 to more than 2000. The on-column LODs and LOQs were from high femtomoles to low picomoles. The analytical accuracies for eight of the ten analytes were determined to be between 89.5 to 114.8% (CV≤7.4%, n = 6). Using a QTOF instrument, the isotopic distribution patterns of these carboxylates, extracted from a (13) C-labeled mouse heart, were successfully determined by UPLC/MS with full-mass detection, indicating the possible utility of this analytical method for metabolic flux analysis. In summary, this work demonstrates an efficient chemical derivatization LC/MS method for metabolomic analysis of these key CCM intermediates in a biological matrix.

Characterizing Vaccinium berry Standard Reference Materials by GC-MS using NIST spectral libraries

A gas chromatography-mass spectrometry (GC-MS)-based method was developed for qualitative characterization of metabolites found in Vaccinium fruit (berry) dietary supplement Standard Reference Materials (SRMs). Definitive identifications are provided for 98 unique metabolites determined among six Vaccinium-related SRMs. Metabolites were enriched using an organic liquid/liquid extraction, and derivatized prior to GC-MS analysis. Electron ionization (EI) fragmentation spectra were searched against EI spectra of authentic standards compiled in the National Institute of Standards and Technology's mass spectral libraries, as well as spectra selected from the literature. Metabolite identifications were further validated using a retention index match along with prior probabilities and were compared with results obtained in a previous effort using collision-induced dissociation (CID) MS/MS datasets from liquid chromatography coupled to mass spectrometry experiments. This manuscript describes a nontargeted metabolite profile of Vaccinium materials, compares results among related materials and from orthogonal experimental platforms, and discusses the feasibility and development of using mass spectral library matching for nontargeted metabolite identification.

Composition of sugars, organic acids, and total phenolics in 25 wild or cultivated berry species

Sugars, organic acids, and total phenolic content in fruit of 25 wild and cultivated berry species were identified and quantified with high-performance liquid chromatograph. The composition of sugars, organic acids, and total phenolic compounds in various species of Vaccinium, Rubus, Ribes, and Fragaria genus was evaluated. Additonally, total phenolics of less known berry species of the Morus, Amelanchier, Sorbus, Sambucus, Rosa, Lycium, Actinidia, and Aronia genus were determined in wild growing as well as in cultivated fruits. Significant differences in the concentration of sugars and organic acids were detected among the berry species. Glucose and fructose were the most abundant sugars in berry fruits and the major organic acids were malic and citric acid. However, in kiwi fruit, sucrose represented as much as 71.9% of total sugars. Sorbitol has been detected and quantified in chokeberry, rowanberry, and eastern shadbush fruit. The highest content of total analyzed sugars was determined in rowanberry fruit, followed by dog rose, eastern shadbush, hardy kiwifruit, American cranberry, chokeberry, and jostaberry fruit. Rowanberry stands out as the fruit with the highest content of total analyzed organic acids, followed by jostaberry, lingonberry, red gooseberry, hardy kiwifruit, and black currant. The berries of white gooseberry, black currant, red currant, and white currant had the lowest sugar/organic acid ratio and were thus perceptively the sourest species analyzed. On the other hand, the species with highest sugar/organic acid ratio were goji berry, eastern shadbush, black mulberry, and wild grown blackberry. The highest amounts of total phenols were quantified in chokeberry fruit. Wild strawberry, raspberry, and blackberry had 2- to 5-fold more total phenolics compared to cultivated plants.

PRACTICAL APPLICATION

The fruit of analyzed berry species contained different levels of sugars, organic acids, and total phenolics. Moreover, it has been demonstrated that wild grown species generally contain more phenolics than cultivated ones. This information is interesting for nutritionists as well as berry growers and breeders who can promote the cultivation of species and new cultivars with higher phenolic content.

Role of chromatography in the development of Standard Reference Materials for organic analysis

The certification of chemical constituents in natural-matrix Standard Reference Materials (SRMs) at the National Institute of Standards and Technology (NIST) can require the use of two or more independent analytical methods. The independence among the methods is generally achieved by taking advantage of differences in extraction, separation, and detection selectivity. This review describes the development of the independent analytical methods approach at NIST, and its implementation in the measurement of organic constituents such as contaminants in environmental materials, nutrients and marker compounds in food and dietary supplement matrices, and health diagnostic and nutritional assessment markers in human serum. The focus of this review is the important and critical role that separation science techniques play in achieving the necessary independence of the analytical steps in the measurement of trace-level organic constituents in natural matrix SRMs.

Analysis of organic acids in fruit juices by liquid chromatography-mass spectrometry: an enhanced tool for authenticity testing

Organic acid analysis plays a fundamental role in the testing of authenticity of fruit juices. Analytical methods used routinely for organic acids suffer from poor reproducibility, often give false positives/negatives for tartaric acid, and do not offer the possibility of analyte confirmation. There are conflicting reports in the literature on the presence/absence of tartaric acid in pomegranate juice, a potential indicator of adulteration with grape juice. In this work, a method based on stable isotope dilution liquid chromatography-tandem mass spectrometry is described for citric, malic, quinic, and tartaric acid in fruit juices. Validation data including precision and recovery in six types of juice are presented. Tartaric and quinic acids were confirmed in pomegranate juice at concentrations of 1-5 and ∼1 mg/L, respectively. These concentrations are much lower than those resulting from adulteration with grape juice and apple juice, respectively, at the 5% level. A separate method for isocitric acid in orange juice based on the single standard addition method is also described.