Oxidation-Reduction Potential of Ascorbic Acid (Vitamin C)

Abstract Background Hypovitaminosis C and vitamin C deficiency are common in critically ill patients and associated with organ dysfunction. Low vitamin C status often goes unnoticed because determination is challenging. The static oxidation reduction potential (sORP) reflects the amount of oxidative stress in the blood and is a potential suitable surrogate marker for vitamin C. sORP can be measured rapidly using the RedoxSYS system, a point-of-care device. This study aims to validate a model that estimates plasma vitamin C concentration and to determine the diagnostic accuracy of sORP to discriminate between decreased and higher plasma vitamin C concentrations. Methods Plasma vitamin C concentrations and sORP were measured in a mixed intensive care (IC) population. Our model estimating vitamin C from sORP was validated by assessing its accuracy in two datasets. Receiver operating characteristic (ROC) curves with areas under the curve (AUC) were constructed to show the diagnostic accuracy of sORP to identify and rule out hypovitaminosis C and vitamin C deficiency. Different cut-off values are provided. Results Plasma vitamin C concentration and sORP were measured in 117 samples in dataset 1 and 43 samples in dataset 2. Bias and precision (SD) were 1.3 ± 10.0 µmol/L and 3.9 ± 10.1 µmol/L in dataset 1 and 2, respectively. In patients with low plasma vitamin C concentrations, bias and precision were − 2.6 ± 5.1 µmol/L and − 1.1 ± 5.4 µmol in dataset 1 (n = 40) and 2 (n = 20), respectively. Optimal sORP cut-off values to differentiate hypovitaminosis C and vitamin C deficiency from higher plasma concentrations were found at 114.6 mV (AUC 0.91) and 124.7 mV (AUC 0.93), respectively. Conclusion sORP accurately estimates low plasma vitamin C concentrations and can be used to screen for hypovitaminosis C and vitamin C deficiency in critically ill patients. A validated model and multiple sORP cut-off values are presented for subgroup analysis in clinical trials or usage in clinical practice.

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Establishment of a Method for Measuring Antioxidant Capacity in Urine, Based on Oxidation Reduction Potential and Redox Couple I2/KI

Bioinorganic Chemistry and Applications ◽

10.1155/2016/7054049 ◽

2016 ◽

Vol 2016 ◽

pp. 1-9 ◽

Cited By ~ 3

Author(s):

Tinghui Cao ◽

Min He ◽

Tianyu Bai ◽

Hui Liu

Keyword(s):

Vitamin C ◽

Antioxidant Capacity ◽

Linear Relationship ◽

Concentration Ratio ◽

Reduction Potential ◽

Redox Couple ◽

New Method ◽

Diabetic Patients ◽

Oxidation Reduction ◽

Oxidation Reduction Potential

Objectives. To establish a new method for determination of antioxidant capacity of human urine based on the redox couple I2/KI and to evaluate the redox status of healthy and diseased individuals. Methods. The method was based on the linear relationship between oxidation reduction potential (ORP) and logarithm of concentration ratio of I2/KI. ORP of a solution with a known concentration ratio of I2/KI will change when reacted with urine. To determine the accuracy of the method, both vitamin C and urine were reacted separately with I2/KI solution. The new method was compared with the traditional method of iodine titration and then used to measure the antioxidant capacity of urine samples from 30 diabetic patients and 30 healthy subjects. Results. A linear relationship was found between logarithm of concentration ratio of I2/KI and ORP (R2=0.998). Both vitamin C and urine concentration showed a linear relationship with ORP (R2=0.994 and 0.986, resp.). The precision of the method was in the acceptable range and results of two methods had a linear correlation (R2=0.987). Differences in ORP values between diabetic group and control group were statistically significant (P<0.05). Conclusions. A new method for measuring the antioxidant capacity of clinical urine has been established.

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Estimating Vitamin C Status in Critically Ill Patients with a Novel Point-of-Care Oxidation-Reduction Potential Measurement

Nutrients ◽

10.3390/nu11051031 ◽

2019 ◽

Vol 11 (5) ◽

pp. 1031 ◽

Cited By ~ 1

Author(s):

Sander Rozemeijer ◽

Angélique M. E. Spoelstra-de Man ◽

Sophie Coenen ◽

Bob Smit ◽

Paul W. G. Elbers ◽

...

Keyword(s):

Oxidative Stress ◽

Vitamin C ◽

Critically Ill ◽

Critically Ill Patients ◽

Reduction Potential ◽

Point Of Care ◽

Plasma Vitamin ◽

Vitamin C Deficiency ◽

Oxidation Reduction ◽

Oxidation Reduction Potential

Vitamin C deficiency is common in critically ill patients. Vitamin C, the most important antioxidant, is likely consumed during oxidative stress and deficiency is associated with organ dysfunction and mortality. Assessment of vitamin C status may be important to identify patients who might benefit from vitamin C administration. Up to now, vitamin C concentrations are not available in daily clinical practice. Recently, a point-of-care device has been developed that measures the static oxidation-reduction potential (sORP), reflecting oxidative stress, and antioxidant capacity (AOC). The aim of this study was to determine whether plasma vitamin C concentrations were associated with plasma sORP and AOC. Plasma vitamin C concentration, sORP and AOC were measured in three groups: healthy volunteers, critically ill patients, and critically ill patients receiving 2- or 10-g vitamin C infusion. Its association was analyzed using regression models and by assessment of concordance. We measured 211 samples obtained from 103 subjects. Vitamin C concentrations were negatively associated with sORP (R2 = 0.816) and positively associated with AOC (R2 = 0.842). A high concordance of 94–100% was found between vitamin C concentration and sORP/AOC. Thus, plasma vitamin C concentrations are strongly associated with plasma sORP and AOC, as measured with a novel point-of-care device. Therefore, measuring sORP and AOC at the bedside has the potential to identify and monitor patients with oxidative stress and vitamin C deficiency.

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High levels of seminal oxidation reduction potential (ORP) in infertile men with clinical varicocele

10.26226/morressier.5912d9e7d462b80292386967 ◽

2017 ◽

Author(s):

Ramadan Saleh

Keyword(s):

Reduction Potential ◽

Infertile Men ◽

Oxidation Reduction ◽

Oxidation Reduction Potential

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On the Elucidation of the pH Dependence of the Oxidation-Reduction Potential of Cytochrome c at Alkaline pH

Journal of Biological Chemistry ◽

10.1016/s0021-9258(18)99768-1 ◽

1966 ◽

Vol 241 (18) ◽

pp. 4180-4185

Author(s):

Karl G. Brandt ◽

Paul C. Parks ◽

Georg H. Czerlinski ◽

George P. Hess

Keyword(s):

Cytochrome C ◽

Reduction Potential ◽

Ph Dependence ◽

Alkaline Ph ◽

Oxidation Reduction ◽

Oxidation Reduction Potential

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In situ measurements of oxidation–reduction potential and hydrogen peroxide concentration as tools for revealing LPMO inactivation during enzymatic saccharification of cellulose

Biotechnology for Biofuels ◽

10.1186/s13068-021-01894-1 ◽

2021 ◽

Vol 14 (1) ◽

Author(s):

Adnan Kadić ◽

Anikó Várnai ◽

Vincent G. H. Eijsink ◽

Svein Jarle Horn ◽

Gunnar Lidén

Keyword(s):

Reduction Potential ◽

Enzymatic Saccharification ◽

The State ◽

Enzyme Inactivation ◽

Ex Situ ◽

Process Economics ◽

Complete Inactivation ◽

Oxidation Reduction ◽

Oxidation Reduction Potential

Abstract Background Biochemical conversion of lignocellulosic biomass to simple sugars at commercial scale is hampered by the high cost of saccharifying enzymes. Lytic polysaccharide monooxygenases (LPMOs) may hold the key to overcome economic barriers. Recent studies have shown that controlled activation of LPMOs by a continuous H2O2 supply can boost saccharification yields, while overdosing H2O2 may lead to enzyme inactivation and reduce overall sugar yields. While following LPMO action by ex situ analysis of LPMO products confirms enzyme inactivation, currently no preventive measures are available to intervene before complete inactivation. Results Here, we carried out enzymatic saccharification of the model cellulose Avicel with an LPMO-containing enzyme preparation (Cellic CTec3) and H2O2 feed at 1 L bioreactor scale and followed the oxidation–reduction potential and H2O2 concentration in situ with corresponding electrode probes. The rate of oxidation of the reductant as well as the estimation of the amount of H2O2 consumed by LPMOs indicate that, in addition to oxidative depolymerization of cellulose, LPMOs consume H2O2 in a futile non-catalytic cycle, and that inactivation of LPMOs happens gradually and starts long before the accumulation of LPMO-generated oxidative products comes to a halt. Conclusion Our results indicate that, in this model system, the collapse of the LPMO-catalyzed reaction may be predicted by the rate of oxidation of the reductant, the accumulation of H2O2 in the reactor or, indirectly, by a clear increase in the oxidation–reduction potential. Being able to monitor the state of the LPMO activity in situ may help maximizing the benefit of LPMO action during saccharification. Overcoming enzyme inactivation could allow improving overall saccharification yields beyond the state of the art while lowering LPMO and, potentially, cellulase loads, both of which would have beneficial consequences on process economics.

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