Plasma ascorbic acid: measurement, stability and clinical utility revisited

Early Detection Is the Best Prevention-Characterization of Oxidative Stress in Diabetes Mellitus and Its Consequences on the Cardiovascular System

Previous studies demonstrated an important role of oxidative stress in the pathogenesis of cardiovascular disease (CVD) in diabetic patients due to hyperglycemia. CVD remains the leading cause of premature death in the western world. Therefore, diabetes mellitus-associated oxidative stress and subsequent inflammation should be recognized at the earliest possible stage to start with the appropriate treatment before the onset of the cardiovascular sequelae such as arterial hypertension or coronary artery disease (CAD). The pathophysiology comprises increased reactive oxygen and nitrogen species (RONS) production by enzymatic and non-enzymatic sources, e.g., mitochondria, an uncoupled nitric oxide synthase, xanthine oxidase, and the nicotinamide adenine dinucleotide phosphate (NADPH) oxidase (NOX). Considering that RONS originate from different cellular mechanisms in separate cellular compartments, adequate, sensitive, and compartment-specific methods for their quantification are crucial for early detection. In this review, we provide an overview of these methods with important information for early, appropriate, and effective treatment of these patients and their cardiovascular sequelae.

Evaluation of a high-performance liquid chromatography method for urinary oxalate determination and investigation regarding the pediatric reference interval of spot urinary oxalate to creatinine ratio for screening of primary hyperoxaluria

BACKGROUND

Urinary oxalate can provide important clues for the screening and monitoring of children with primary hyperoxaluria (PH), which is a potentially life-threatening condition. However, little effort has been devoted to improve the oxalate assay in recent years. We have proposed a reliable and cost-effective high-performance liquid chromatography (HPLC) method for urinary oxalate determination.

METHODS

Urine specimens were centrifuged after one-step derivatization, and the supernatants were subjected to HPLC analysis.

RESULTS

The method was validated with consistent linearity from 0.0625 to 2.0 mmol/L with coefficients of variation ≤7.73%, good recovery, low carryover, satisfactory sample stability, and analytical specificity. The lower limit of quantification and the limit of detection were 0.03130 and 0.0156 mmol/L, respectively. Imprecision values were ≤2.92% and ≤16.6% for externally and internally produced controls, respectively. The pediatric reference interval of spot urinary oxalate to creatinine ratios was established together with its application in screening of PH in patients with renal diseases, revealing its successful deployment in our laboratory.

CONCLUSIONS

This reliable HPLC method could serve as a significant tool to determine urinary oxalate levels for screening and monitoring of children with PH in routine clinical laboratories.

Analytical Methods Used in Determining Antioxidant Activity: A Review

The study of antioxidants and their implications in various fields, from food engineering to medicine and pharmacy, is of major interest to the scientific community. The present paper is a critical presentation of the most important tests used to determine the antioxidant activity, detection mechanism, applicability, advantages and disadvantages of these methods. Out of the tests based on the transfer of a hydrogen atom, the following were presented: the Oxygen Radical Absorption Capacity (ORAC) test, the Hydroxyl Radical Antioxidant Capacity (HORAC) test, the Total Peroxyl Radical Trapping Antioxidant Parameter (TRAP) test, and the Total Oxyradical Scavenging Capacity (TOSC) test. The tests based on the transfer of one electron include the Cupric Reducing Antioxidant Power (CUPRAC) test, the Ferric Reducing Antioxidant Power (FRAP) test, the Folin-Ciocalteu test. Mixed tests, including the transfer of both a hydrogen atom and an electron, include the 2,2'-Azinobis-(3-ethylbenzothiazoline-6-sulfonic acid (ABTS) test, and the [2,2-di(4-tert-octylphenyl)-1-picrylhydrazyl] (DPPH) test. All these assays are based on chemical reactions and assessing the kinetics or reaching the equilibrium state relies on spectrophotometry, presupposing the occurrence of characteristic colours or the discolouration of the solutions to be analysed, which are processes monitored by specific wavelength adsorption. These assays were successfully applied in antioxidant analysis or the determination of the antioxidant capacity of complex samples. As a complementary method in such studies, one may use methods based on electrochemical (bio)sensors, requiring stages of calibration and validation. The use of chemical methods together with electrochemical methods may result in clarification of the operating mechanisms and kinetics of the processes involving several antioxidants.

Seasonal variations in nutritional status and oxidative stress in patients on hemodialysis: Are they related?

OBJECTIVE

Seasonal variations in body composition and parameters that reflect nutritional status are well established in patients on hemodialysis (HD). However, to our knowledge, no study has assessed the changes in oxidative stress (OS). The aims of this study were to assess seasonal variations in OS, body composition, and other nutritional parameters.

METHODS

Seasonal variations in fat tissue mass (FTM), fat tissue index (FTI), adipose tissue mass (ATM), lean tissue mass (LTM), lean tissue index (LTI), body cell mass (BCM), overhydration (OH) volume, and OS (blood levels of derivatives of reactive oxygen metabolites [d-ROMs], thiobarbituric reactive substances, plasma protein reduced thiol content [THIOLS], and ferric reducing ability of plasma) were assessed in 45 patients on HD, 70 y of age (60.5-76.5 y).

RESULTS

FTM (P < 0.001), FTI (P < 0.001), and ATM (P < 0.001) significantly increased, whereas LTI (P < 0.001), LTM (P < 0.001), BCM (P < 0.001), and OH volume (P = 0.004) significantly decreased over the season. Additionally, significant seasonal variations in the levels of d-ROMs (P = 0.02) and THIOLS (P = 0.02) were found. Levels of d-ROMs were found to be a significant predictor of LTM and BCM (β = -0.57; 95% confidence interval [CI], -1.08 to -0.06; P = 0.03; β = -0.04; 95% CI, -0.075 to -0.006; P = 0.02). Furthermore, hip circumference was found to be the most significant predictor of the level of d-ROMs (β = 2.66; 95% CI; 0.28-5.04; P = 0.03) and waist-to-height ratio (β = 251; 95% CI, 16.6-477.2; P = 0.03) and serum prealbumin levels of THIOLS (β = 263; 95% CI, 6.8-521.1; P = 0.04).

CONCLUSION

These results suggest seasonal variations in OS in patients on HD and a possible interaction between OS and nutritional status in these patients.

The testicular protective effects of standardised hydroalcoholic extract of Ziziphus jujuba Mill against adriamycin-induced toxicity

In this study, because of the anti-inflammatory and antioxidant effect of the Ziziphus jujuba (ZJ), we assessed the protective properties of the ZJ extract against testis toxicity caused by Adriamycin in the rat. Twenty rats were grouped into (a) control, (b) Adriamycin, (c) ZJ group and (d) treatment group in which Adriamycin was administrated and the ZJ hydroalcoholic extract was used for three weeks. On the 21st day, two testes were removed to determine the oxidation markers and pathological evaluation. The levels of sex hormones were determined. Epididymis also was crushed, and its spermatozoa were evaluated as concentration, motility and normality. Adriamycin increased oxidative stress markers as well as Luteinising hormone, and follicle-stimulating hormone and decreased testosterone levels compared to control. In the treated group, the levels of the above markers improved. The decreased number and motility of spermatozoa in treatment group increased, and the increased rate of abnormal spermatozoa in this group decreased. Pathological evaluations also show the healing process of damaged testicular tissue in the group receiving the ZJ extract. The ZJ extract relatively improves oxidative stress, sperm characteristics, hormonal alternation and pathological changes. These findings reveal the probable role of ZJ effective compounds in repairing tissue damage.

The Effects of Surgery on Plasma/Serum Vitamin C Concentrations: A Systematic Review and Meta-Analysis

Vitamin C (ascorbic acid) is a water soluble vitamin with an array of biological functions. A number of proposed factors contribute to the vitamin’s plasma bioavailability and ability to exert optimal functionality. The aim of this review was to systematically assess plasma vitamin C levels post-surgery compared with pre-surgery/ the magnitude and timeframe of potential changes in concentration. We searched the PUBMED, SCOPUS, SciSearch and the Cochrane Library databases between 1970 to April 2020 for relevant research papers. Prospective studies, control groups and true placebo groups derived from controlled trials that reported means and standard deviations of plasma vitamin C concentrations pre and post operatively were included into the meta-analysis. Data were grouped into short-term (≤7 days) and long term (> 7 days) post-operative follow-up. 23 of 31 studies involving 642 patients included in the systematic review were suitable for meta-analysis. Pooled data from the meta-analysis revealed a mean depletion of plasma vitamin C concentration of -17.99 µmol/L (39% depletion) (CI = -22.81, -13.17) (trial arms = 25, n = 565, p < 0.001) during the first post-operative week and -18.80 µmol/L (21% depletion) (-25.04, -12.56) (trial arms = 6, n = 166, p < 0.001) 2-3 months post-operatively. Subgroup analyses revealed that these depletions occurred following different types of surgery, however, high heterogeneity was observed amongst trials assessing concentration change during the first post-operative week. Overall, our results warrant larger, long term investigations of changes in post-operative plasma vitamin C concentrations and their potential effects on clinical symptomology.

Activity-Based Sensing of Ascorbate by Using Copper-Mediated Oxidative Bond Cleavage

Ascorbate is an important biological reductant and enzyme cofactor. Although direct detection through ascorbate-mediated reduction is possible, this approach suffers from poor selectivity due to the wide range of cellular reducing agents. To overcome this limitation, we leverage reduction potential of ascorbate to mediate a copper-mediated oxidative bond cleavage of ether-caged fluorophores. The copper(II) complexes supported by a {bis(2-pyridylmethyl)}benzylamine or a {bis(2-pyridylmethyl)}(2-methoxybenzyl)amine ligand were identified as an ascorbate responsive unit and their reaction with ascorbate yields a copper-based oxidant that enables rapid benzylic oxidation and the release of an ether-caged dye (coumarin or fluorescein). The copper-mediated bond cleavage is specific to ascorbate and the trigger can be readily derivatized for tuning photophysical properties of the probes. The probes were successfully applied for the fluorometric detection of ascorbate in commercial food samples, human plasma, and serum, and within live cells by using confocal microscopy and flow cytometry.

Paper-based platforms with coulometric readout for ascorbic acid determination in fruit juices

There is growing interest in the development of simple, fast, sustainable and low-cost analytical methodologies on paper-based platforms. However, sensitive detection strategies that fit properly with these devices are still required. In this work, a calibration-free method is proposed for analytical determinations performed on paper-based electrochemical devices, in this case, for ascorbic acid. Carbon ink is deposited on a hydrophilic working area of the paper delimited with a hydrophobic wax. This maskless procedure is fast and cuts down ink waste. The connection of this working electrode to the potentiostat is provided by reusable gold-plated connector headers that provide also the reference and counter electrodes. The thickness of the paper substrate defines the electrochemical cell and confines a sample volume, ideal for thin-layer coulometry. Controlled-potential coulometry is performed applying a potential of +0.6 V for 50 s. The charge is calculated by measuring the area under the fast chronoamperogram and the concentration is determined following Faraday's law (known number of transferred electrons). This methodology was applied to the determination of ascorbic acid, with a limit of detection of 40 μM. Its concentration in commercial fruit juices can be directly determined in diluted samples. The absence of matrix effects is observed by comparing the results obtained before and after enzymatic reaction of the sample with cucumber ascorbate oxidase. Good accuracy and precision makes this method suitable for quality control of ascorbic acid in commercial juices. Underexploited coulometric readout can be applied as a fast (calibration-free) and low-cost (standards not required) transduction principle for the newly developed paper devices.

Gender Differences in Plasma Vitamin C Concentrations and Cognitive Function: A Pilot Cross-Sectional Study in Healthy Adults

BACKGROUND

A number of investigations have highlighted the importance of vitamin C in maintaining brain health. Biologically, vitamin C has exhibited roles in neuromodulation, neurodevelopment, vascular support, and neuroprotection. Vitamin C's contribution to cognitive function in both cognitively intact and impaired cohorts has previously been assessed, with little focus on gender variability.

OBJECTIVE

The present study explored the interaction between gender and plasma vitamin C on cognitive performance, and the effect of different amounts of plasma vitamin C (adequate/inadequate) on various cognitive tasks by gender.

METHODS

This retrospective analysis was conducted in healthy adults (n = 80, female = 52, male = 28, 24-96 y) with a range of blood plasma vitamin C concentrations. Cognitive assessments included the Swinburne University Computerized Cognitive Assessment Battery (SUCCAB) and 2 pen-and-paper tests, the Symbol Digits Modalities Test (SDMT) and the Hopkins Verbal Learning Test-Revised (HVLT-R). Food-frequency questionnaires were used to elucidate dietary consumption.

RESULTS

After adjusting for a number of potential covariates such as age, number of prescribed medications and dose of vitamin C supplementation, results indicated a significant interaction (P < 0.001) between plasma vitamin C and gender on cognitive function, on both the computerized and pen-and-paper assessments. A novel finding was that the performance of males with inadequate plasma vitamin C was poorer on tasks involving components of memory (short/delayed), inhibition, and visual perception, whereas females presenting with inadequate vitamin C were more compromised on tasks involving psychomotor performance/motor speed. Additionally, females with adequate vitamin C concentrations exhibited higher performance than males on tasks involving recall, recognition, attention, and focus.

CONCLUSIONS

Further larger-scale investigations are required to establish a cause-and-effect relation and to elucidate whether differences in cognitive function between genders may be attributed to plasma vitamin C status.This trial was registered at https://www.anzctr.org.au/Trial/Registration/TrialReview.aspx?id=369440&isReview=true as ACTRN12615001140549.

Changes in the Selected Antioxidant Defense Parameters in the Blood of Patients after High Resolution Computed Tomography

Ionizing radiation generated during high resolution computed tomography (HRCT) scanning may have an indirect effect on the mechanisms regulating the oxidative-antioxidant balance in the human body, which is one of the necessary factors ensuring the maintenance of its homeostasis. The aim of the study was to analyze the response of antioxidant systems through the determination of the antioxidant markers in the blood of patients exposed to oxidative stress resulting from the routine HRCT examination of the chest. Blood of 35 people aged 60.77 ± 10.81 taken before and at four time points after the examination constituted the test material. The determination of the total antioxidant capacity expressed as ferric reducing ability of plasma (FRAP) and ferric reducing antioxidant activity and ascorbic acid concentration (FRASC) were performed together with an examination of catalase activity and the concentration of the reduced glutathione. The organism’s response to ionizing radiation was associated with a significant decrease in the antioxidant markers’ levels at all time-points and showed a significant negative correlation depending on the radiation dose. Visible down-regulation of these markers is a response to increased oxidative stress. In light of the obtained results, the measurement of the selected markers of antioxidant defense may be a useful parameter of oxidative stress caused by ionizing radiation.

Plasma Vitamin C Concentrations and Cognitive Function: A Cross-Sectional Study

Vitamin-C is a water soluble molecule that humans have lost the ability to produce. Vitamin-C plays a role in CNS functions such as neuronal differentiation, maturation, myelin formation and modulation of the catecholaminergic systems. A recent systematic review by our team indicated the need for further research into the relationship between plasma vitamin C and cognition in cognitively intact participants using plasma vitamin C concentrations instead of estimates derived from food-frequency-questionnaires (FFQ), and more sensitive cognitive assessments suitable for cognitive abilities vulnerable to aging. It was hypothesized that higher plasma vitamin C concentrations would be linked with higher cognitive performance. This cross-sectional trial was conducted on healthy adults (n = 80, Female = 52, Male = 28, 24-96 years) with a range of plasma Vitamin C concentrations. Cognitive assessments included The Swinburne-University-Computerized-Cognitive-Assessment-Battery (SUCCAB) and two pen and paper tests, the Symbol-Digits-Modalities-Test (SDMT) and Hopkins-Verbal-Learning-Test-Revised (HVLT-R). The pen and paper assessments were conducted to establish whether their scores would correlate with the computerized tasks. Plasma-Vitamin C concentrations were measured using two biochemical analyses. Participants were grouped into those with plasma vitamin-C concentrations of adequate level (≥28 μmol/L) and deficient level (<28 μmol/L). The SUCCAB identified a significantly higher performance ratio (accuracy/reaction-time) in the group with adequate vitamin-C levels vs. deficient vitamin-C on the choice reaction time (M = 188 ± 4 vs. 167 ± 9, p = 0.039), immediate recognition memory (M = 81 ± 3 vs. 68 ± 6, p = 0.03), congruent Stroop (M = 134 ± 3 vs. 116 ± 7, p = 0.024), and delayed recognition tasks (M = 72 ± 2 vs. 62 ± 4, p = 0.049), after adjusting for age (p < 0.05). Significantly higher scores in immediate recall on the HVLT-R (M = 10.64 ± 0.16 vs. 9.17 ± 0.37, p = 0.001), delayed recall (M = 9.74 ± 0.22 vs. 7.64 ± 0.51, p < 0.001), total recall (M = 27.93 ± 0.48 vs. 24.19 ± 1.11, p = 0.003) were shown in participants with adequate plasma Vitamin-C concentrations, after adjusting for vitamin-C supplementation dose (p < 0.05). Similarly, higher SDMT scores were observed in participants with adequate plasma Vitamin-C concentrations (M = 49.73 ± 10.34 vs. 41.38 ± 5.06, p = 0.039), after adjusting for age (p < 0.05). In conclusion there was a significant association between vitamin-C plasma concentrations and performance on tasks involving attention, focus, working memory, decision speed, delayed and total recall, and recognition. Plasma vitamin C concentrations obtained through vitamin C supplementation did not affect cognitive performance differently to adequate concentrations obtained through dietary intake. Clinicaltrials.gov Unique Identifier: ACTRN 12615001140549, URL: https://www.anzctr.org.au/Trial/Registration/TrialReview.aspx?id=369440.

Evaluation of oxidative stress and the microenvironment in oral submucous fibrosis

BACKGROUND

Oral Submucous fibrosis (OSF) is a chronic inflammatory mucosal disease of unknown etiology. Statistics show cases of OSF which has a high rate of overall prevalence and increase the chance of malignant transformation. As we know malignant cells is situated in a very complex microenvironment with altered metabolic pathway including intermediates which participate in oxidative stress process which enhances metabolic rewiring and promotes tumor progression. This study aims to evaluate the tumor microenvironment and their role in metabolic reprogramming.

METHODS

This study was conducted on the serum sample of OSF (n = 20) compared to the healthy group (n = 20) using ELISA. The serum levels of intermediate by-products of metabolic pathway and oxidative stress induced biomolecular damage products were determined. The sensitivity of results was analyzed by correlating it with markers of metabolic status (Glucose, Total cholesterol, Total protein).

RESULTS

Metabolic pathway intermediates molecules like Fatty Acids (FAA), Ascorbic acid, Citrate, Oxaloacetate (OAA), levels were significantly high in the serum of OSF cases. This indicated that intermediates act as a metabolic switch that drives cells to adapt malignant transformation pathway. Markers related to oxidative DNA damage (8-hydroxy-2' -deoxyguanosine), Oxidative lipid peroxidation (8-epi-Prostaglandin F2α), and Protein carbonyl were significantly up-regulated. This significant increase in oxidative stress marker revealed the reprogramming of the metabolic pathway for fulfilling the nutritional requirement of cancer cells. A further significant correlation was observed with metabolic products confirmed altered metabolic status.

CONCLUSION

Our findings could identify the differentiating intermediate pathway metabolites and oxidative damage to biomolecules that are leading to rewiring of metabolism in the OSF group. Findings described in the study can be helpful to explain further the molecular aspects that lead to the progression of OSF towards carcinogenesis.

Apple intake improves antioxidant parameters in hemodialysis patients without affecting serum potassium levels

Oxidative stress (OS) is associated with increased morbidity and mortality in hemodialysis (HD) patients, and the consumption of fruits seems to improve OS due to their antioxidant properties. Therefore, we hypothesized that Fuji apple intake improves OS markers in HD patients due to its polyphenolic compounds without increasing serum potassium levels. This trial was a 1-group, pre- and posttest comparison between 16 patients who had been on hemodialysis for at least 3 months without any acute illness or hyperkalemia. Each volunteer consumed 2 Fuji apples (~360 g) per day for 1 week. Blood samples were collected at the baseline period and after 8 days for the measurement of total antioxidant status, ascorbic acid, catalase, glutathione peroxidase, superoxide dismutase, reduced glutathione, total oxidant status, oxidative stress index, potassium, phosphorus, uric acid, glucose, and fructosamine. For tolerance evaluation, participants were asked about their bowel habits. Apple intake increased glutathione peroxidase (P = .006) and superoxide dismutase activities (P = .006) and ascorbic acid levels (P = .002). No significant changes were observed in uric acid, potassium, phosphorus, glucose, and fructosamine levels. Additionally, there was a decrease in the catalase activity (P = .021) and in the total antioxidant status values (P = .004). However, increased total oxidant status (P = .003) and oxidative stress index (P = .033) levels were observed after apple intake. In conclusion, the intake of 2 Fuji apples per day for 1 week was well tolerated and improved antioxidant parameters in HD patients without affecting serum potassium levels.

Appropriate Handling, Processing and Analysis of Blood Samples Is Essential to Avoid Oxidation of Vitamin C to Dehydroascorbic Acid

Vitamin C (ascorbate) is the major water-soluble antioxidant in plasma and its oxidation to dehydroascorbic acid (DHA) has been proposed as a marker of oxidative stress in vivo. However, controversy exists in the literature around the amount of DHA detected in blood samples collected from various patient cohorts. In this study, we report on DHA concentrations in a selection of different clinical cohorts (diabetes, pneumonia, cancer, and critically ill). All clinical samples were collected into EDTA anticoagulant tubes and processed at 4 °C prior to storage at −80 °C for subsequent analysis by HPLC with electrochemical detection. We also investigated the effects of different handling and processing conditions on short-term and long-term ascorbate and DHA stability in vitro and in whole blood and plasma samples. These conditions included metal chelation, anticoagulants (EDTA and heparin), and processing temperatures (ice, 4 °C and room temperature). Analysis of our clinical cohorts indicated very low to negligible DHA concentrations. Samples exhibiting haemolysis contained significantly higher concentrations of DHA. Metal chelation inhibited oxidation of vitamin C in vitro, confirming the involvement of contaminating metal ions. Although EDTA is an effective metal chelator, complexes with transition metal ions are still redox active, thus its use as an anticoagulant can facilitate metal ion-dependent oxidation of vitamin C in whole blood and plasma. Handling and processing blood samples on ice (or at 4 °C) delayed oxidation of vitamin C by a number of hours. A review of the literature regarding DHA concentrations in clinical cohorts highlighted the fact that studies using colourimetric or fluorometric assays reported significantly higher concentrations of DHA compared to those using HPLC with electrochemical detection. In conclusion, careful handling and processing of samples, combined with appropriate analysis, is crucial for accurate determination of ascorbate and DHA in clinical samples.

A Simplified Sample Preparation Method for the Assessment of Plasma Ascorbic Acid in Clinical Settings

BACKGROUND

Vitamin C deficiency is difficult to diagnose on the basis of clinical presentation alone and requires plasma levels for confirmation. Reference laboratories typically specify shipment of plasma on dry ice. This requirement may complicate clinic work flow and delay vitamin C measurement. Additionally, patients with vitamin C deficiency may experience unnecessary testing and increased health-care costs, as other diagnoses are often considered first. We examined an alternative, more practical shipping method.

METHODS

Plasma was collected from 17 healthy volunteers by use of heparin tubes with gel separators, and all tubes were centrifuged immediately to separate the plasma layer from the cells. Baseline vitamin C was measured in plasma obtained immediately after specimen collection. Remaining sample tubes were held in Styrofoam containers with cold packs for 30 h or 48 h, followed by vitamin C measurement. Additional samples were exposed to conditions that simulated harsher shipping conditions.

RESULTS

Mean plasma vitamin C was 69.6 μmol/L (SD = 21.5 μmol/L). Vitamin C losses were 5.4% at 30 h (SD = 5.55%, P < 0.05) and 7.6% at 48 h (SD = 5.56%, P < 0.05), which is slightly more than freeze-and-thaw treatment (average loss of 1.4%, SD = 6.9%, NS). The vitamin C method had an intraday variation of 1.88%. Vigorous shaking of 2 samples for 24 h resulted in a -1.9% change in 1 sample, and a +4.1% change in another sample. Exposure of the shipping container to elevated temperature (35 °C for 30 h) did not change the internal temperature of the container.

CONCLUSIONS

The shipping procedure uses routine sample handling, standard vacutainers, and can be replicated by health-care centers seeking to evaluate patient vitamin C status.

Vitamin D deficiency, oxidative stress and antioxidant status: only weak association seen in the absence of advanced age, obesity or pre-existing disease

Vitamin D deficiency (plasma 25-hydroxycholecalciferol (25(OH)D)70 % of participants were vitamin D deficient. No significant correlations and no biomarker differences across 25(OH)D quartiles or groups were seen except for total antioxidant status. A weak direct association (r 0·252, P<0·05) was observed between 25(OH)D and FRAP, and those in the lowest 25(OH)D quartile and group had significantly lower FRAP values. Results did not reveal a clear link between vitamin D status and oxidative stress biomarkers in the absence of advanced age, obesity and disease, though some evidence of depleted antioxidant status in those with vitamin D deficiency was seen. Poor antioxidant status may pre-date increased oxidative stress. Study of effects of correction of deficiency on antioxidant status and oxidative stress in vitamin D-deficient but otherwise healthy subjects is needed.

Effects of a novel ascorbate-based protocol on infarct size and ventricle function in acute myocardial infarction patients undergoing percutaneous coronary angioplasty

INTRODUCTION

This study was designed to test the hypothesis that high-dose ascorbate prior to reperfusion followed by low chronic oral doses ameliorate myocardial reperfusion injury (MRI) in acute myocardial infarction patients subjected to primary percutaneous coronary angioplasty (PCA).

MATERIAL AND METHODS

A randomized double-blind placebo-controlled and multicenter clinical trial was performed on acute myocardial infarction (AMI) patients who underwent PCA. Sodium ascorbate (320 mmol/l, n = 53) or placebo (n = 46) was infused 30 min prior to PCA. Blood samples were drawn at enrolment (M1), after balloon deflation (M2), 6-8 h after M2 (M3) and at discharge (M4). Total antioxidant capacity of plasma (ferric reducing ability of plasma - FRAP), erythrocyte reduced glutathione (GSH) and plasma ascorbate levels were determined in blood samples. Cardiac magnetic resonance (CMR) was performed at 7-15 days and 2-3 months following PCA. Ninety-nine patients were enrolled. In 67 patients, the first CMR was performed, and 40 patients completed follow-up.

RESULTS

The ascorbate group showed significantly higher ascorbate and FRAP levels and a decrease in the GSH levels at M2 and M3 (p < 0.05). There were no significant differences in the infarct size, indexed end-systolic volume and ejection fraction at both CMRs. There was a significant amelioration in the decreased ejection fraction between the first and second CMR in the ascorbate group (p < 0.05).

CONCLUSIONS

Ascorbate given prior to reperfusion did not show a significant difference in infarct size or ejection fraction. However, it improved the change in ejection fraction determined between 7-15 days and 2-3 months. This result hints at a possible functional effect of ascorbate to ameliorate MRI.

Ascorbic acid and vitamin C-containing beverages delay the leucomalachite green reaction to detect latent bloodstains

The leucomalachite green (LMG) test is one of catalytic tests for the detection of latent bloodstains and generally used in forensic field because of convenience and cost/time-effectiveness. However, contamination of latent bloodstains at crime scenes can interfere with the LMG reaction, resulting in false-negative or false-positive decisions. Herein, we examined if ascorbic acid and vitamin C (l-ascorbic acid or ascorbate)-containing beverages affect the LMG reaction. Ascorbic acid showed the inhibitory activities on the LMG reaction in a dose-dependent manner. Similarly, vitamin C-containing beverages also inhibited the LMG reaction and the inhibitory effects were proportional to the concentrations of vitamin C in beverages. It was also identified that as incubation time after adding LMG reagent to the mixtures of blood and ascorbic acid or beverages was increased, the inhibitory effects of ascorbic acid vitamin C-containing beverages on LMG test were disappeared. These results suggest that the LMG reaction is delayed but not stopped by ascorbic acid and vitamin C-containing beverages. Neither incubation at room temperature around 20-25°C nor the addition of acetic acid affects the inhibitory activity of ascorbic acid on LMG reaction. We also showed that ascorbic acid does not affect DNA stability, allowing us to obtain full short tandem repeat (STR) profiles through amplification of DNA using commercial STR kits. In conclusion, ascorbic acid and vitamin C-containing beverages delayed the LMG reaction, suggesting that it should be considered that negative results of LMG test could be false negative due to contamination of bloodstains with inhibitory factors on LMG test.

Enhancing translational research in paediatric rheumatology through standardization

The past decade has seen many successes in translational rheumatology, from dramatic improvements in outcomes brought about by novel biologic therapies, to the discovery of new monogenic inflammatory disorders. Advances in molecular medicine, combined with progress towards precision care, provide an excellent opportunity to accelerate the translation of biological understanding to the bedside. However, although the field of rheumatology is a leader in the standardization of data collection and measures of disease activity, it lags behind in standardization of biological sample collection and assay performance. Uniform approaches are necessary for robust collaborative research, particularly in rare diseases. Standardization is also critical to increase reproducibility between centres, a prerequisite for clinical implementation of translational research. This Perspectives article emphasizes the need for standardization and implementation of best practices, presented in the context of lessons learned from international biorepository networks.

Setup and validation of a convenient sampling procedure to promptly and effectively stabilize vitamin C in blood and plasma specimens stored at routine temperatures

Vitamin C (ascorbic acid, AA) is very labile in nature and decays quickly after blood withdrawal. To ensure AA stability, the current procedure prescribes immediate plasma acidification followed by sample storage at ultra-low temperature. The aim of this study was to set up a pre-analytical procedure to promptly stabilize AA at routine temperatures while minimizing both specimen manipulation and instrumental requirement. Blood from healthy subjects was collected in lithium-heparin gel separator tubes containing or not different reducing agents (dithioerythritol, tris(2-carboxyethyl)phosphine, n-acetylcysteine and sodium thiosulfate). Plasma AA stability during blood and plasma storage at routine temperatures was evaluated. Plasma AA concentration was assayed by RP-HPLC-UV under ion suppression conditions. Each of the reductants tested was able to slow down the ex vivo degradation of plasma AA; dithioerythritol was the most effective. Five to 10 mmol/L dithioerythritol did not interfere with blood separation and allowed plasma AA to be stabilized up to 6 h, 24 h and 60 days at room temperature, +4 °C and -25 °C, respectively. The method worked well even in case of delayed blood separation and/or incomplete vacutainer filling. The procedure is feasible and reliable. Of special usefulness in clinical and epidemiological studies, prompt plasma manipulation after blood withdrawal or special storage equipments are not required. Graphical Abstract Collecting blood in tubes containing a reducing agent is a feasible method to promptly and effectively stabilize plasma vitamin C at routine temperature.

Amelioration of persistent left ventricular function impairment through increased plasma ascorbate levels following myocardial infarction

PURPOSE

Percutaneous coronary angioplasty (PCA) has been demonstrated to reduce mortality and morbidity and thereby improve the prognosis of patients undergoing acute myocardial infarctions (AMIs). However, this procedure paradoxically increases the initial damage as the result of a condition known as 'myocardial reperfusion injury'. Oxidative stress may contribute to the mechanism of this injury. The goal of the present study was to ascertain whether high plasma ascorbate levels could ameliorate the reperfusion injuries that occur after the successful restoration of blood flow.

METHODS

Patients from three clinical centers of the public health system were included in the study. The groups were formed by either-sex patients with a diagnosis of ST-segment elevation myocardial infarction with an indication for primary PCA. Only the patients who presented with their first myocardial infarction were enrolled. Ascorbate was administered through an infusion given prior to the restoration of the coronary flow, which was then followed by oral treatment with vitamin C (500 mg/12 hours) plus vitamin E (400 IU/day) for 84 days. The left ventricular ejection fraction (LVEF) was determined by using cardiac magnetic resonance on days 6 and 84 following the onset of the reperfusion. In addition, the microvascular function was assessed by an angiographic evaluation using the Thrombolysis In Myocardial Infarction (TIMI) myocardial perfusion grade (TMPG). The results were grouped according to the plasma ascorbate concentration achieved immediately following the onset of reperfusion into either the HA group (high ascorbate, >1 mmol/l) or the LA group (low ascorbate, <1 mmol/l). The biochemical parameters were analyzed throughout the protocol.

RESULTS

The LVEF of the HA group was significantly higher than that of the LA group, values on day 84 in the HA group were 33% higher than those of the LA group. The amelioration of the LVEF was accompanied by an improvement in the microvascular dysfunction, after PCA, 95% of the patients in the HA group achieved a TMPG of 2-3, in the LA group only 79% of patients showed a TMPG of 2-3.

CONCLUSIONS

These data are consistent with the protective effect of high plasma levels of ascorbate against the oxidative challenge caused by reperfusion injury in patients subjected to PCA following an AMI. Further studies are needed to elucidate the mechanism accounting for this beneficial antioxidant effect.

LacaScore: a novel plasma sample quality control tool based on ascorbic acid and lactic acid levels

INTRODUCTION

Metabolome analysis is complicated by the continuous dynamic changes of metabolites in vivo and ex vivo. One of the main challenges in metabolomics is the robustness and reproducibility of results, partially driven by pre-analytical variations.

OBJECTIVES

The objective of this study was to analyse the impact of pre-centrifugation time and temperature, and to determine a quality control marker in plasma samples.

METHODS

Plasma metabolites were measured by gas chromatography-mass spectrometry (GC-MS) and analysed with the MetaboliteDetector software. The metabolites, which were the most labile to pre-analytical variations, were further measured by enzymatic assays. A score was calculated for their use as quality control markers.

RESULTS

The pre-centrifugation temperature was shown to be critical in the stability of plasma samples and had a significant impact on metabolite concentration profiles. In contrast, pre-centrifugation delay had only a minor impact. Based on the results of this study, whole blood should be kept on wet ice and centrifuged within maximum 3 h as a prerequisite for preparing EDTA plasma samples fit for the purpose of metabolome analysis.

CONCLUSIONS

We have established a novel blood sample quality control marker, the LacaScore, based on the ascorbic acid to lactic acid ratio in plasma, which can be used as an indicator of the blood pre-centrifugation conditions, and hence the suitability of the sample for metabolome analyses. This method can be applied in research institutes and biobanks, enabling assessment of the quality of their plasma sample collections.

The ratio of oxidized and reduced forms of selected antioxidants as a possible marker of oxidative stress in humans

Oxidative stress is an imbalance between reactive oxygen species exposure and the ability of organisms to detoxify the reactive intermediates and to repair the oxidative damage of biologically important molecules. Many clinical studies of oxidative stress unfortunately provide conflicting and contradictory results. The ability of antioxidant systems to adequately respond to oxidative stress can be used in laboratory diagnostics. In the present review, methods using the ratio of reduced and oxidized forms of uric acid, ascorbic acid, glutathione and coenzyme Q10 as suitable indicators of oxidative stress are discussed. From the mentioned publications it is evident that suitable sample preparation prior to analysis is crucial.

Evaluation of 2,6-dichlorophenolindophenol acetate as a substrate for acetylcholinesterase activity assay

Ellman's method is a standard protocol for the determination of cholinesterases activity. Though the method is ready for laboratory purposes, it has some drawbacks as well. In the current article, 2,6-dichloroindophenol acetate is performed as a chromogenic substrate suitable for acetylcholinesterase (AChE) activity examination. Michaelis constant and maximal velocity for 2,6-dichloroindophenol acetate were determined (38.0 µM and 244 pkat) and compared to the values for acetythiocholine (K(m) 0.18 mM; V(max) 5.1 nkat). Docking for 2,6-dichloroindophenol acetate and human AChE was done as well. In conclusion, 2,6-dichloroindophenol acetate seems to be suitable chromogenic substrate for AChE and spectrophotometry and based on this it can be easily performed whenever AChE activity should be tested.

Overview of the in vitro stability of commonly measured vitamins and carotenoids in whole blood

Background

The pre-analytical stabilities of vitamins A, E, K, B1, B2, B6, B12, C, carotenoids and folates in whole blood were studied. The aim of this work was to provide clear and workable pre-analytical procedures specifying optimal delay before freezing for laboratories which perform themselves such analyses or which receive and transfer such specimens to referral laboratories.

Methods

The stability of vitamins was studied in whole blood at room temperature after light exposure up to 24 h (vitamin C), 48 h (vitamins A, E, B1, B2, B6 and carotenoids) and 72 h (vitamins K, B12, red blood cell (RBC) and serum folates). Vitamin C stability after baseline acidification was analysed up to 48 h. Changes observed were compared to a clinical cut-off defined as total change limit based on a combination of analytical performance and within-subject variation.

Results

Clinically and statistically significant changes occurred only in vitamins C (−22.5%), B6 (+9.9%) and serum folates (−16.8%) concentrations after 6, 24 and 48 h, respectively. Vitamins A, E, K, B1, B2, B12, RBC folates and carotenoids showed good stability up to 48 or 72 h. Vitamin C in acidified serum conserved at room temperature appeared unstable. The optimal condition for acidified vitamin C conservation was at less than −20℃.

Conclusion

The majority of vitamins remain stable for up to 48 h. Vitamin C quantification requires serum acidification followed by freezing as soon as possible. Freezing, respectively, within 12 h and 24 h for determination of plasma vitamin B6 and serum folates concentrations is recommended.

Acute application of antioxidants protects against hyperoxia-induced reduction of plasma nitrite concentration

We investigated the effects of acute intake of antioxidants on hyperoxia-induced oxidative stress, reduction of plasma nitrite and change in arterial stiffness. Twelve healthy males randomly consumed either placebo or an oral antioxidant cocktail (vitamin C, 1000 mg; vitamin E, 600 IU; alpha-lipoic acid, 600 mg). Every therapy was consumed once, a week apart, in a cross-over design, 30 min before the experiment. The volunteers breathed 100% normobaric oxygen between 30th and 60th min of 1-h study protocol. Plasma levels of nitrite, lipid peroxides (LOOH) and vitamin C, arterial stiffness (indicated by augmentation index, AIx) and arterial oxygen (Ptc O2 ) pressure were measured before and after hyperoxia. Exposure to oxygen caused a similar increase of Ptc O2 in both placebo and antioxidants groups, confirming comparable exposure to hyperoxia (438 ± 100 versus 455 ± 83 mm Hg). Vitamin C was increased in the antioxidants group confirming successful application of antioxidants (69 ± 14 versus 57 ± 15 μm). Hyperoxia resulted in increased AIx and LOOH and decreased nitrite in placebo (-32 ± 11 versus -47 ± 13%, 72 ± 7 versus 62 ± 6 μm H2 O2 and 758 ± 184 versus 920 ± 191 nm, respectively), but not in the antioxidants group (-42 ± 13 versus -50 ± 13%, 64 ± 9 versus 61 ± 8 μm H2 O2 and 847 ± 156 versus 936 ± 201 nm, respectively). The acute intake of selected antioxidants was effective in preserving bioavailabity of ˙NO and vascular function, against hyperoxia-induced oxidative stress.

Antioxidants in food: content, measurement, significance, action, cautions, caveats, and research needs

There are a multitude of antioxidants in foods, especially in foods of plant origin. Higher intake of antioxidant-rich foods is clearly associated with better health and functional longevity. The specific agents and mechanisms responsible are not yet clear, but there is convincing evidence that including more plant-based, antioxidant-rich foods, herbs, and beverages in the diet is effective in promoting health and lowering risk of various age-related diseases. The content of some individual antioxidants, such as vitamin C, in food can be measured, but it is not feasible to attempt to measure each antioxidant separately, and methods have been developed to assess the "total antioxidant content" of foods. One of the most widely used methods is the ferric reducing/antioxidant power (FRAP) assay, which is relatively simple, quick, sensitive, and inexpensive to perform. There are many published studies that have used the FRAP assay, and these have generated a very large database of total antioxidant content of foods that can help guide food choices for increased antioxidant intake. The FRAP assay has also been used to assess the bioavailability of antioxidants in foods and to investigate the effects of growing conditions, storage, processing, and cooking method on the total antioxidant content of food. The test can be employed as a quality control check device, and to detect adulteration of food. Furthermore, in a modified form (FRASC), the assay can measure ascorbic acid content almost simultaneously with the total antioxidant content of the sample. In this chapter, basic concepts of oxidation and the role of antioxidants, as well as the types and action of different antioxidants in foods will be reviewed briefly, and the underpinning concepts and evidence for health benefits of increased intake of dietary antioxidants will be discussed, with some focus on vitamin C, and also in the context of our evolutionary development. The basic concepts and limitations of measuring "total antioxidant content" of food will be presented. The FRAP assay and the modified version FRASC will be described, and the total antioxidant content (as the FRAP value) of a range of foods will be presented. Finally, issues of bioavailability and redox balance will be discussed in relation to the biological significance and molecular action of antioxidants in foods, some caution and caveats are presented about overcoming biological barriers to absorption of antioxidant phytochemicals, and research needs to further our understanding in the important area of food, antioxidants, and health will be highlighted.

Myths, artifacts, and fatal flaws: identifying limitations and opportunities in vitamin C research

Research progress to understand the role of vitamin C (ascorbic acid) in human health has been slow in coming. This is predominantly the result of several flawed approaches to study design, often lacking a full appreciation of the redox chemistry and biology of ascorbic acid. In this review, we summarize our knowledge surrounding the limitations of common approaches used in vitamin C research. In human cell culture, the primary issues are the high oxygen environment, presence of redox-active transition metal ions in culture media, and the use of immortalized cell lines grown in the absence of supplemental ascorbic acid. Studies in animal models are also limited due to the presence of endogenous ascorbic acid synthesis. Despite the use of genetically altered rodent strains lacking synthesis capacity, there are additional concerns that these models do not adequately recapitulate the effects of vitamin C deprivation and supplementation observed in humans. Lastly, several flaws in study design endemic to randomized controlled trials and other human studies greatly limit their conclusions and impact. There also is anecdotal evidence of positive and negative health effects of vitamin C that are widely accepted but have not been substantiated. Only with careful attention to study design and experimental detail can we further our understanding of the possible roles of vitamin C in promoting human health and preventing or treating disease.

Oxidative stress-related biomarkers in essential hypertension and ischemia-reperfusion myocardial damage

Cardiovascular diseases are a leading cause of mortality and morbidity worldwide, with hypertension being a major risk factor. Numerous studies support the contribution of reactive oxygen and nitrogen species in the pathogenesis of hypertension, as well as other pathologies associated with ischemia/reperfusion. However, the validation of oxidative stress-related biomarkers in these settings is still lacking and novel association of these biomarkers and other biomarkers such as endothelial progenitor cells, endothelial microparticles, and ischemia modified albumin, is just emerging. Oxidative stress has been suggested as a pathogenic factor and therapeutic target in early stages of essential hypertension. Systolic and diastolic blood pressure correlated positively with plasma F2-isoprostane levels and negatively with total antioxidant capacity of plasma in hypertensive and normotensive patients. Cardiac surgery with extracorporeal circulation causes an ischemia/reperfusion event associated with increased lipid peroxidation and protein carbonylation, two biomarkers associated with oxidative damage of cardiac tissue. An enhancement of the antioxidant defense system should contribute to ameliorating functional and structural abnormalities derived from this metabolic impairment. However, data have to be validated with the analysis of the appropriate oxidative stress and/or nitrosative stress biomarkers.

Identification of evidence-based biospecimen quality-control tools: a report of the International Society for Biological and Environmental Repositories (ISBER) Biospecimen Science Working Group

Control of biospecimen quality that is linked to processing is one of the goals of biospecimen science. Consensus is lacking, however, regarding optimal sample quality-control (QC) tools (ie, markers and assays). The aim of this review was to identify QC tools, both for fluid and solid-tissue samples, based on a comprehensive and critical literature review. The most readily applicable tools are those with a known threshold for the preanalytical variation and a known reference range for the QC analyte. Only a few meaningful markers were identified that meet these criteria, such as CD40L for assessing serum exposure at high temperatures and VEGF for assessing serum freeze-thawing. To fully assess biospecimen quality, multiple QC markers are needed. Here we present the most promising biospecimen QC tools that were identified.

Heme oxygenase microsatellite polymorphism, oxidative stress, glycemic control, and complication development in type 2 diabetes patients

Heme oxygenase-1 (HMOX-1) is activated by oxidative stress, and gene responsiveness is reportedly determined by the number of dinucleotide (GT(n)) repeats in its highly polymorphic promoter region. "Short" (S; GT(n)<25) alleles reportedly associate with higher response, lower oxidative stress, lower risk of type 2 diabetes mellitus (type 2DM), and better glycemic control and outcome, but data are conflicting. We investigated GT(n) in type 2DM subjects (all ethnic Chinese) in relation to basal glycemic control, oxidative stress, and outcome during up to 9 years' follow-up. Fasting blood from 418 type 2 DM subjects was collected at entry for GT(n) genotyping, glycated hemoglobin, glucose, lipids, and biomarkers of oxidative stress and antioxidants. A subset (n=368) was followed for up to 9 years for incident complications or death. GT(n) genotype distribution was 128, 182, and 108 for, respectively, S/S, S/L, and L/L. No significant differences in glycemic control, lipids, or oxidative stress were seen across genotypes. During follow-up, 168/368 subjects developed complications. No association was seen with GT(n). No difference in plasma HO-1 was seen between genotypes in a small substudy (S/S n=21 vs L/L n=23). Glycated hemoglobin and lymphocytic DNA damage was higher (p<0.05) at entry in the incident complications group. No other significant differences were seen in oxidative stress or antioxidants. Data do not support the postulated link between HMOX-1 microsatellite polymorphism and type 2 DM or the putative beneficial effect of the S allele on glycemic control, oxidative stress, or outcome in type 2 DM patients, at least in this particular population.

Gupta S, S. Young I, Maraini G, Camparini M, Jayanthi R, John N, Fitzpatrick KE, Chakravarthy U, Ravilla TD, Fletcher AE. Prevalence and risk factors for vitamin C deficiency in north and south India: a two centre population based study in people aged 60 years and over

BACKGROUND

Studies from the UK and North America have reported vitamin C deficiency in around 1 in 5 men and 1 in 9 women in low income groups. There are few data on vitamin C deficiency in resource poor countries.

OBJECTIVES

To investigate the prevalence of vitamin C deficiency in India.

DESIGN

We carried out a population-based cross-sectional survey in two areas of north and south India. Randomly sampled clusters were enumerated to identify people aged 60 and over. Participants (75% response rate) were interviewed for tobacco, alcohol, cooking fuel use, 24 hour diet recall and underwent anthropometry and blood collection. Vitamin C was measured using an enzyme-based assay in plasma stabilized with metaphosphoric acid. We categorised vitamin C status as deficient (<11 µmol/L), sub-optimal (11-28 µmol/L) and adequate (>28 µmol/L). We investigated factors associated with vitamin C deficiency using multivariable Poisson regression.

RESULTS

The age, sex and season standardized prevalence of vitamin C deficiency was 73.9% (95% confidence Interval, CI 70.4,77.5) in 2668 people in north India and 45.7% (95% CI 42.5,48.9) in 2970 from south India. Only 10.8% in the north and 25.9% in the south met the criteria for adequate levels. Vitamin C deficiency varied by season, and was more prevalent in men, with increasing age, users of tobacco and biomass fuels, in those with anthropometric indicators of poor nutrition and with lower intakes of dietary vitamin C.

CONCLUSIONS

In poor communities, such as in our study, consideration needs to be given to measures to improve the consumption of vitamin C rich foods and to discourage the use of tobacco.

The protective role of ascorbic acid in burn-induced testicular damage in rats

OBJECTIVE

To investigate the ability of ascorbic acid to protect the testes from damage in severe burns.

DESIGN

Experimental study.

SETTING

University of Lagos Medical School, Department of Anatomy.

ANIMALS

28 adult male Wistar rats (250-300 g).

INTERVENTION

Third degree burn was induced on 40% body surface area of rats and they were given ascorbic acid at 4 mg/kg over 8 weeks.

MAIN OUTCOME MEASURED

Weight of reproductive organs and epididymal sperm parameters were measured. Oxidative status was assayed and a semi-quantitative assessment of histologic changes was also carried out.

RESULTS

Burn caused severe seminiferous tubular damage, especially germ cell loss (p<0.05). This was matched by significant reduction in sperm density and morphology (p<0.05). Burn also increased oxidative stress, with elevated malondialdehyde (MDA) levels (p<0.01) and changes in catalase and superoxide dismutase enzyme levels. Ascorbic acid prevented the changes in all sperm parameters. It normalized MDA levels (p<0.01) and attenuated changes in the levels of catalase and superoxide dismutase. Ascorbic acid treatment also significantly reduced histologic damage to seminiferous tubules.

CONCLUSION

This study shows that severe thermal injury causes significant testicular damage and impairs spermatogenesis. It also shows that ascorbic acid protects the testis from such damage and therefore has the potential to be a useful adjunct therapy during treatment of young males with severe burns.

Simple and rapid method for the determination of uric acid-independent antioxidant capacity

Determination of the relative contribution of uric acid level increases to the total measured antioxidative activity could be very useful for testing antioxidative products and their effect on human health. The aim of this report is to present a simple spectrophotometric method that combines the measurement of total antioxidative capacity of a sample by ferric reducing/antioxidative power (FRAP) assay, with the uricase-reaction (specific elimination of uric acid), in order to establish and correct for the contribution of uric acid in FRAP values. We measured FRAP values, with (uric acid-independent antioxidant capacity, TAC-UA) and without (total antioxidant capacity, TAC) uricase treatment, and expressed it as μmol/L of uric acid equivalents. In such way, it was possible to determine both total and uric acid-independent antioxidant capacity, plasma uric acid (UA, as the difference between TAC and TAC-UA), and the ratio of the uric acid in total antioxidant capacity (UA/TAC).

Factors affecting the stability of drugs and drug metabolites in biological matrices

Evaluation of the stability of drugs and drug metabolites in a biological matrix is a critical element to bioanalytical method validation. It is critical to understand the most common factors that affect the stability of such analytes in order to properly develop methods for their detection and measurement. The degradation of drugs and drug metabolites in samples can occur through either reversible or irreversible processes. Common factors that affect this stability include temperature, light, pH, oxidation and enzymatic degradation. Special considerations are also required when dealing with chiral molecules, deuterated internal standards and large biomolecules. Relevant examples of these degradation effects and approaches for dealing with them are presented is this review as taken from the fields of pharmaceutical testing, clinical research and forensic analysis. It is demonstrated through these examples how an understanding of the chemical and physical factors that affect sample stability can be used to avoid stability problems and to create robust and accurate methods for the analysis of drugs and related compounds.

Vegetarian diets and public health: biomarker and redox connections

Vegetarian diets are rich in antioxidant phytochemicals. However, they may not act as antioxidants in vivo, and yet still have important signaling and regulatory functions. Some may act as pro-oxidants, modulating cellular redox tone and oxidizing redox sensitive sites. In this review, evidence for health benefits of vegetarian diets is presented from different perspectives: epidemiological, biomarker, evolutionary, and public health, as well as antioxidant. From the perspective of molecular connections between diet and health, evidence of a role for plasma ascorbic acid as a biomarker for future disease risk is presented. Basic concepts of redox-based cell signaling are presented, and effects of antioxidant phytochemicals on signaling, especially via redox tone, sulfur switches and the Antioxidant Response Element (ARE), are explored. Sufficient scientific evidence exists for public health policy to promote a plant-rich diet for health promotion. This does not need to wait for science to provide all the answers as to why and how. However, action and interplay of dietary antioxidants in the nonequilibrium systems that control redox balance, cell signaling, and cell function provide rich ground for research to advance understanding of orthomolecular nutrition and provide science-based evidence to advance public health in our aging population.

Vitamin C deficiency is an under-diagnosed contributor to degenerative disc disease in the elderly

The human aging process is often accompanied by significant increases in degenerative spine disease. The pathophysiology of intervertebral disc degeneration has been extensively studied, but the etiology of this aging-related problem remains poorly understood. The elderly often have lower daily vitamin C intakes and circulating ascorbic acid values than younger people because of problems with poor dentition or mobility, and also are more likely to have underlying sub-clinical diseases that can reduce plasma ascorbate concentrations. Ascorbate is essential for collagen production, and vitamin C deficiency will result in defective connective tissue, including reductions in collagen synthesis and structural stability. It is hypothesised that vitamin C deficiencies may be a key contributing factor in the development of degenerative disk disease (DDD) in the elderly. Once degenerative disc disease has begun, the tissue inflammation that accompanies DDD may further increase vitamin C requirements in the affected patient, thereby creating a cascade of positive feedbacks that potentially accelerates and contributes to further disc degeneration and low-back pain. Aggressive monitoring of patient ascorbate status, as well as more finely-calibrated RDAs for vitamin C that explicitly take into account the patient's age, may be required if aging-related degenerative disk disease is to be minimised.

Plasma vitamin C is lower in postherpetic neuralgia patients and administration of vitamin C reduces spontaneous pain but not brush-evoked pain

OBJECTIVES

Plasma vitamin C concentrations have been suggested to be related to pain modulation in postherpetic neuralgia (PHN), an intractable neuropathic pain syndrome. In this study, we first compared plasma concentrations of vitamin C between healthy volunteers and PHN patients and then designed a symptom-based and mechanism-based approach to assess the analgesic effect of intravenous vitamin C on spontaneous and brush-evoked pain.

METHODS

Study 1 was cross-sectional that enrolled 39 healthy volunteers and 38 PHN patients. Study 2 was a double-blinded, placebo-controlled intervention study, which comprised 41 patients randomly allocated into the ascorbate group and placebo. Each patient received normal saline infusion with or without ascorbate on days 1, 3, and 5 and answered questionnaires that included side effects; numeric rating pain scale (NRS) on spontaneous and brush-evoked pain on days 1, 3, 5, and 7; and patient global impression of change on spontaneous and brush-evoked pain on day 7.

RESULTS

Study 1 revealed that plasma concentrations of vitamin C were significantly lower in patients with PHN than in healthy volunteers (P<0.001). Study 2 showed that ascorbate treatment effectively restored plasma vitamin C concentrations in the patients and decreased spontaneous pain by 3.1 in NRS from baseline to day 7, as compared with a decrease of 0.85 in NRS by placebo treatment (P<0.001). Conversely, ascorbate treatment did not significantly affect brush-evoked pain. Ascorbate treatment also resulted in a better efficacy than placebo in patient global impression of change on spontaneous pain (P<0.001) on day 7 and did not affect brush-evoked pain. No side effects were observed.

CONCLUSIONS

Plasma vitamin C status plays a role in PHN, and intravenous ascorbate helps relieve spontaneous pain in PHN.

Ascorbic Acid in human seminal plasma: determination and its relationship to sperm quality

The objective of the present study was to assess the ascorbic acid (AA) levels in seminal plasma of the fertile and infertile men and to investigate its relationship with sperm count, motility and normal morphology. Semen samples were provided by fertile [smoker (n = 25), nonsmoker (n = 21)] and infertile men [smoker (n = 23), nonsmoker (n = 32)]. A simplified method of reverse phase high performance liquid chromatography (RP-HPLC) procedure using UV detection was applied for the determination of seminal AA. Fertile subjects, smoker or not, demonstrated significantly higher seminal AA levels than any infertile group (p<0.01). Nonsmokers had high, but no significant, mean AA levels in their seminal plasma compared with smokers. Seminal AA in fertile and infertile (smokers or nonsmokers) males correlated significantly with the percentage of spermatozoa with normal morphology (p<0.01). Seminal AA decreased significantly in infertile men. Decrease of seminal plasma AA is a risk factor for low normal morphology of spermatozoa and idiopathic male infertility. Measurement of seminal AA in the seminal plasma of males with a history of subfertility or idiopathic infertility is necessary and can be helpful in fertility assessment.

Impact of plasma and whole-blood anticoagulant counter ion choice on drug stability and matrix effects during bioanalysis

Background: Anticoagulants are used to prevent coagulation in blood samples. The plasma pH may change with a different counter ion and anticoagulant; thus, it is essential to determine effects on drug stability and the matrix effect during the bioanalytical method development. Results: Cross-validation of multiple compounds between different counter ions was performed and no impact from the counter ion nature was demonstrated. Moreover, plasma stabilities and matrix effects for both fluconazole and granisetron were investigated thoroughly in numerous counter ions/anticoagulants (K3ethylenediaminetetraacetic acid [K3EDTA], K2EDTA, NaEDTA, NaHeparin and LiHeparin). Sirolimus, a large cyclic molecule, was also tested in different whole-blood EDTA counter ions. Results showed percentage deviation less than 8.5% and percentage cross-validation less than 8.4%. Conclusion: None of the compounds tested had an impact on the matrix stabilities and matrix effect.