Measurement and stability of plasma reduced, oxidized and total coenzyme Q10 in humans

The Use of the Coenzyme Q10 as a Food Supplement in the Management of Fibromyalgia: A Critical Review

The coenzyme Q₁₀ is a naturally occurring benzoquinone derivative widely prescribed as a food supplement for different physical conditions and pathologies. This review aims to sum up the key structural and functional characteristics of Q₁₀, taking stock of its use in people affected by fibromyalgia. A thorough survey has been conducted, using Pubmed, Scifinder, and ClinicalTrials.gov as the reference research applications and registry database, respectively. Original articles, reviews, and editorials published within the last 15 years, as well as open clinical investigations in the field, if any, were analyzed to point out the lights and shadows of this kind of supplementation as they emerge from the literature.

The Roles of Coenzyme Q in Disease: Direct and Indirect Involvement in Cellular Functions

Coenzyme Q (CoQ) is a key component of the respiratory chain of all eukaryotic cells. Its function is closely related to mitochondrial respiration, where it acts as an electron transporter. However, the cellular functions of coenzyme Q are multiple: it is present in all cell membranes, limiting the toxic effect of free radicals, it is a component of LDL, it is involved in the aging process, and its deficiency is linked to several diseases. Recently, it has been proposed that coenzyme Q contributes to suppressing ferroptosis, a type of iron-dependent programmed cell death characterized by lipid peroxidation. In this review, we report the latest hypotheses and theories analyzing the multiple functions of coenzyme Q. The complete knowledge of the various cellular CoQ functions is essential to provide a rational basis for its possible therapeutic use, not only in diseases characterized by primary CoQ deficiency, but also in large number of diseases in which its secondary deficiency has been found.

Ubiquinol (Reduced Coenzyme Q10) and Cellular Oxygen Consumption in Patients Undergoing Coronary Artery Bypass Grafting

Ubiquinol is a fundamental component of cellular metabolism. Low ubiquinol levels have been associated with mortality. This was a substudy of a randomized trial in patients undergoing coronary artery bypass grafting. We drew blood before and after surgery. Ubiquinol or placebo was added to peripheral blood mononuclear cells for oxygen consumption (OCR) measurements. In vivo ubiquinol levels were lower postsurgery compared to presurgery (0.16 μmol/L [quartiles: 0.02-0.39], P = .01), although the difference disappeared when adjusting for hemoglobin levels (P = .30). There was no difference in presurgical basal (1.0 mL/min/mg [95% confidence interval [CI]: -0.9 to 2.2], P = .08) and maximal (0.5 mL/min/mg [95% CI: -4.3 to 7.3], P = .56) OCR in cells receiving ubiquinol or placebo. There was a difference in postsurgical basal (1.1 mL/min/mg [95% CI: 0.9-1.6], P < .001) and maximal (4.2 mL/min/mg [95% CI: 0.3-7.0], P = .01) OCR between the groups. We found no association between ubiquinol and OCR levels (all P > .05).

Self-reported adherence and biomarker levels of CoQ10 and alpha-tocopherol

PURPOSE

Women with breast cancer were randomized to receive coenzyme Q10 (CoQ10) plus Vitamin E or placebo in a clinical trial. The objective of this evaluation is to examine the association between participant self-reported adherence to the study supplements and changes in plasma biomarker levels.

PATIENTS AND METHODS

Correlation coefficients quantified the association between changes in alpha-tocopherol and CoQ10 levels and the association between self-reported adherence and changes in biomarkers. Participants were categorized by self-reported adherence; Kruskal- Wallis tests compared changes in alpha-tocopherol and CoQ10 levels between self-reported adherence groups.

RESULTS

Women (N=155) provided baseline and post-treatment biomarkers; 147 completed at least one diary. While changes in alpha-tocopherol and CoQ10 levels were moderately correlated, correlations ranged from 0.40 to 0.48, association between self-reported adherence and plasma alpha-tocopherol or CoQ10 levels was weak; correlations ranged from 0.10 to 0.29 at weeks 8, 16, and 24. Some participants with high self-reported adherence actually had decreases in their biomarker levels.

CONCLUSION

These findings support that self-reported adherence is likely to be overestimated. Biological and other measures of adherence that can better identify true adherence to study pills provided in clinical trials are greatly needed as they may assist in improving the interpretation of findings of future clinical trials.

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.

Determination of a method for extraction of coenzyme Q10 in human plasma: optimization of the use of surfactants and other variables

OBJECTIVE

To establish a routine for the extraction of the total levels of CoQ10 in human plasma through the Ultra High Performance Liquid Chromatography (UHPLC).

METHODS

Two extraction protocols were tested: a) methanol: hexane and b) 1-propanol. The following parameters were analyzed: extraction temperature (19ºC and 4ºC), extraction tubes (glass and polypropylene), and surfactants (SDS, Triton X-100, Tween-20) at different concentrations, i.e., 1%, 3%, 5% and 10%.

RESULTS

The results showed that the method of extraction of CoQ10 in a sample of human plasma at 4ºC, using solvents methanol: hexane (85:15, v/v) in the presence of surfactant Tween-20 at 3% and polypropylene tubes showed better efficiency and reproducibility when compared to the method with 1-propanol.

CONCLUSION

By the analyses performed, it was possible to observe that the addition of the surfactant Tween-20 promoted an increase in the recovery of CoQ10 by the methanol:hexane extraction method. This method showed good reproducibility, with a low coefficient of variation and high sensitivity, since CoQ10 was detected in samples of plasma of a control individual using a UV-type detector. The use of UHPLC equipment allowed a total analysis with total run time of 3.5 minutes, enabling the rapid achievement of results, considered mandatory for laboratory routines.

Coenzyme Q10, carotenoid, tocopherol, and retinol levels in cord plasma from multiethnic subjects in Hawaii

Coenzyme Q10 (Q10), carotenoids, tocopherols, and retinol are the major circulating lipid-phase micronutrients (LPM) known to help mitigate oxidative damage and prevent chronic diseases. However, the functions of these compounds in newborns are little understood. This is due, in part, to the paucity of studies reporting their concentrations in this population. We measured Q10, carotenoids, tocopherols, and retinol in cord plasma from 100 multiethnic subjects living in Hawaii using HPLC with diode array and electrochemical detection. Appropriate internal standards were used including, for the first time, custom designed oxidized (UN10) and reduced (UL10) Q10 analogues. These compounds reflected the oxidation of UL10 to UN10 that occurred during sample processing and analysis and thus permitted accurate adjustments of natively circulating Q10 levels. All LPM measured were much lower in cord than in peripheral plasma. Cord plasma levels of total carotenoids, tocopherols, and retinol were approximately 10-fold, 3- to 5-fold and 1.5- to 3-fold lower than those in children or women. Cord plasma levels of total Q10 (TQ10; median, 113 ng/mL) were approximately 2-fold or 7- to 9-fold lower than peripheral plasma levels of neonates or children and adults, respectively. In contrast, the UN10/TQ10 ratio was substantially higher in cord (24%) than in peripheral plasma of children (3-4%) or adults (9%). Among the 5 ethnic groups in our cohort, no differences were observed in the levels of UN10, UL10, or TQ10. However, significant differences in many of the LPM were observed between ethnicities. More research is needed to explain these phenomena.

Analysis of circulating lipid-phase micronutrients in humans by HPLC: review and overview of new developments

Retinol, tocopherols, coenzyme Q10, carotenoids, and vitamin D are lipophilic compounds shown to function as important health-protective agents by mitigating the damaging effects of oxidative and other injury. Scientific interest in evaluating these compounds has resurfaced in recent years, particularly in the nutritional, clinical and epidemiologic fields, and has precipitated the development of a multitude of new analytical techniques. This review considers recent developments in HPLC-based assays since 2007 for the simultaneous determination of these lipid-phase compounds utilizing exclusively serum or plasma as these matrices are mostly used in clinical and epidemiological investigations. We also provide an overview of blood measurements for selected carotenoids, tocopherols, coenzyme Q10 and retinol from the last 15years of healthy umbilical cord blood, children, and adults.

A randomized, double-blind, placebo-controlled study of oral coenzyme Q10 to relieve self-reported treatment-related fatigue in newly diagnosed patients with breast cancer

BACKGROUND

Coenzyme Q10 (CoQ10) is a common antioxidant supplement with known cardioprotective effects and potential anticancer benefits.

OBJECTIVES

We performed a randomized, double-blind, placebo-controlled study of oral CoQ10 in female breast cancer patients with the primary objective of determining CoQ10's effects on self-reported fatigue, depression, and quality of life (QOL). Methods Eligible women with newly diagnosed breast cancer and planned adjuvant chemotherapy were randomized to oral supplements of 300 mg CoQ10 or placebo, each combined with 300 IU vitamin E, divided into 3 daily doses. Treatment was continued for 24 weeks. Blood tests, QOL measures, and levels of plasma CoQ10 and vitamin E were obtained at baseline and at 8, 16, and 24 weeks. Mixed-effects models were used to assess treatment differences in outcomes over time.

RESULTS

Between September 2004 and March 2009, 236 women were enrolled. Treatment arms were well balanced with respect to age (range, 28-85 years), pathologic stage (stage 0, 91%; stage 1, 8%; stage II, 1%), ethnicity (white, 87%; black, 11%; Hispanic, 2%), and planned therapy. Baseline CoQ10 levels in the CoQ10 and placebo arms were 0.70 and 0.73 microg/mL, respectively; the 24-week CoQ10 levels were 1.83 and 0.79 microg/mL, respectively. There were no significant differences between the CoQ10 and placebo arms at 24 weeks for scores on the Profile of Mood States-Fatigue questionnaire (least squares means, 7.08 vs 8.24, P = .257), the Functional Assessment of Chronic Illness Therapy-Fatigue tool (37.6 vs 37.6, P = .965), the Functional Assessment of Cancer Therapy-Breast Cancer instrument (111.9 vs 110.4, P = .577), or the Center for Epidemiologic Studies-Depression scale (11.6 vs 12.3, P = .632).

CONCLUSIONS

Supplementation with conventional doses of CoQ10 led to sustained increases in plasma CoQ10 levels but did not result in improved self-reported fatigue or QOL after 24 weeks of treatment.

Coenzyme Q10 in human blood: native levels and determinants of oxidation during processing and storage

Coenzyme Q10 (Q10) is present in the circulation mainly in its reduced form (ubiquinol-10; UL10), but oxidizes quickly ex vivo to ubiquinone-10 (UN10). Therefore, native UL10:UN10 ratios, used as markers of redox status and disease risk, are difficult to measure. We established an RP-(U)HPLC method with coulometric detection to measure natively circulating UL10 and UN10 concentrations by adding a ubiquinol/ubiquinone mixture as an internal standard immediately after plasma preparation. This allowed adjustment for unavoidable artificial UL10 oxidation as well as for total losses (or gains) of analytes during sample storage, processing, and analysis because the internal standards exactly paralleled the chemical behavior of Q10. This technique applied to blood (n = 13) revealed Q10 levels of 680-3300 nM with a mean UL10:UN10 ratio of 95:5, which was inversely associated with total Q10 (r=-0.69; p=0.004). The oxidation of UL10 to UN10 was equimolar, increased by O(2), and decreased by lower temperatures or various degassing methods. Although UL10 was stable in blood or when pure in organic solvents at 22 degrees C, its oxidation was catalyzed dose dependently by alpha-tocopherol and butylated hydroxytoluene, particularly when present in combination. Key structural features for the catalytic pro-oxidant properties of phenolic antioxidants included two substituents vicinal to the phenolic hydroxyl group.

Environmental contaminants and redox status of coenzyme Q10 and vitamin E in Inuit from Nunavik

The Inuit are heavily exposed to potentially prooxidant contaminants such as methylmercury (MeHg) and polychlorinated biphenyls (PCB) through their traditional diet. This diet is also an abundant source of n-3 polyunsaturated fatty acids (n-3 PUFA), selenium, and antioxidants, which might reduce cardiovascular risk. Although Inuit from Nunavik have low concentrations of plasma oxidized low-density lipoprotein (OxLDL) and elevated glutathione-related antioxidant defenses, the variance in OxLDL was predicted by PCB and blood glutathione, leaving the issue of contaminant-associated oxidative stress unresolved. The objective of the study was to assess oxidative stress in these Inuit by measuring the plasma concentrations and redox states of alpha-tocopherol and coenzyme Q10 (CoQ10), 2 sensitive biomarkers of oxidative stress, in relation to exposure. Plasma lipophilic antioxidants were determined by high-performance liquid chromatography-coupled electrochemical detection; and their relations to PCB, MeHg, n-3 PUFA, selenium, and OxLDL were assessed by multivariate analyses. Ubiquinol-10, ubiquinone-10, and ubiquinone-10 to CoQ10(total) ratio were elevated as compared with white populations but showed no associations with PCB, MeHg, or n-3 PUFA. Ubiquinol-10 (beta = .23, P = .007) and CoQ10(total) (beta = .27, P = .009) were predicted by blood selenium; and alpha-tocopherol, by PCB (beta = 4.12, P = .0002), n-3 PUFA (beta = 9.16, P = .02), and OxLDL (beta = 3.04, P = .05). Unexpectedly, the alpha-tocopheryl quinone to alpha-tocopherol ratio, in the reference range, was negatively predicted by PCB (beta = -0.41, P = .02). Using sensitive biomarkers of redox alterations, we found no evidence for MeHg- or PCB-associated oxidative stress in these Inuit. However, despite robust blood antioxidant defenses, the unusually elevated ubiquinone-10 to CoQ10(total) ratio (0.21 +/- 0.11) suggests some form of oxidative stress of unknown origin.

Seasonal mercury exposure and oxidant-antioxidant status of James Bay sport fishermen

The effects of a moderate seasonal exposure to methylmercury on plasma low-density lipoprotein (LDL) oxidation and cardiovascular risk indices are not known. The objective of the study was to assess the effects of a seasonal exposure to mercury at similar dose reported to increase cardiovascular risk through fish consumption. Effects on lipoprotein cholesterol and fatty acid profiles, LDL oxidation, and blood oxidant-antioxidant balance were to be assessed in sport fishermen presenting normal blood selenium and omega-3 fatty acid contents. Thirty-one healthy James Bay sport fishermen were assessed for within-subject longitudinal seasonal variations in hair and blood mercury, plasma oxidized LDL, lipophilic antioxidants, homocysteine, blood selenium, and glutathione peroxidase and reductase activities determined before and after the fishing season and compared by matched-pair tests. Hair mercury doubled during the fishing season (2.8+/-0.4 microg/g, P<.0001). Baseline blood selenium, homocysteine, and erythrocyte fatty acid profiles did not change. Plasma high-density lipoprotein cholesterol increased (+5%, P=.05), whereas very low-density lipoprotein cholesterol and oxidized LDL decreased (-8%, P=.05; -18%, P=.008). Blood glutathione peroxidase (+9.7%, P=.001), glutathione reductase (+7.2%, P<.0001), and total glutathione (+45% P<.0001) increased during the fishing season. Plasma total coenzyme Q10 (+13%, P=.02), ubiquinone-10 (+67%, P=.03), and beta-carotene (+46%, P=.01) also increased, whereas vitamin E status was unaffected. Pairwise correlations revealed no association between mercury exposure and any of the biomarkers investigated. In contrast, strong predictors of cardiovascular risk such as high-density lipoprotein cholesterol, oxidized LDL, and glutathione peroxidase improved during the fishing season despite elevated methylmercury exposure. The beneficial effects of seasonal fishing activity and fish consumption on cardiovascular health may suppress detrimental effects of concomitant moderate methylmercury exposure.

Mechanisms of oxidative modification of low density lipoproteins under conditions of oxidative and carbonyl stress

Low-molecular-weight aldehydes (glyoxal, methylglyoxal, 3-deoxyglucosone) generated on autooxidation of glucose under conditions of carbonyl stress react much more actively with amino groups of L-lysine and epsilon-amino groups of lysine residues of apoprotein B-100 in human blood plasma low density lipoproteins (LDL) than their structural analogs (malonic dialdehyde (MDA), 4-hydroxynonenal) resulting on free radical oxidation of lipids under conditions of oxidative stress. Glyoxal-modified LDL aggregate in the incubation medium with a significantly higher rate than LDL modified by MDA, and MDA-modified LDL are markedly more poorly absorbed by cultured human macrophages and significantly more slowly eliminated from the rat bloodstream upon intravenous injection. Studies on kinetics of free radical oxidation of rat liver membrane phospholipids have shown that ubiquinol Q(10) is the most active lipid-soluble natural antioxidant, and suppression of ubiquinol Q(10) biosynthesis by beta-hydroxy-beta-methylglutaryl coenzyme A reductase inhibitors (statins) is accompanied by intensification of lipid peroxidation in rat liver biomembranes and in LDL of human blood plasma. Injection of ubiquinone Q(10) protects the human blood plasma LDL against oxidation and prevents oxidative stress-induced damages to rat myocardium. A unified molecular mechanism of atherogenic action of carbonyl-modified LDL in disorders of lipid and carbohydrate metabolism is discussed.

Ubiquinol-10/lipids ratios in consecutive patients with different angiographic findings

OBJECTIVE

Information concerning un-supplemented plasma concentrations of ubiquinol-10 in coronary artery disease patients is still controversial. The aim of this study is to determine the levels of plasma ubiquinol-10 and ratios of ubiquinol-10 to plasma lipids in consecutive patients with different angiographic findings.

SUBJECTS AND METHODS

Thirty-six consecutive patients who underwent coronary angiography were split in two groups with different atherosclerotic changes. These patients were un-supplemented with antioxidants and were not treated by lipid-lowering medication. We have measured a plasma level of ubiquinol-10 using high-performance liquid chromatography with coulometric detection. Conventional plasma lipids, markers of oxidative stress and other widely accepted risk factors of atherosclerosis have been determined too.

RESULTS

Plasma ubiquinol-10 to low-density lipoprotein cholesterol (LDL-C) ratios in patients with different angiographic findings have been found as 180+/-69 and 132+/-43, respectively (p=0.020). The ubiquinol-10/LDL-C ratio was significantly lower in angiographically positive patients. There were also significant differences in ubiquinol-10 per total cholesterol (109+/-47 and 80+/-26, respectively; p=0.031), per triglycerides (426+/-191 and 237+/-86, respectively; p=0.002) and per the sum of triglycerides and total cholesterol (86+/-35 and 61+/-20, respectively; p=0.013).

CONCLUSIONS

There have not been found any significant differences between levels of widely accepted risk factors for genesis and progress of atherosclerotic changes in these two groups of patients. Only the level of triglycerides and the total cholesterol minus high-density lipoprotein cholesterol/high-density lipoprotein cholesterol ratio were significantly higher in patients with stenosis. This ratio correlated with the ubiquinol-10/LDL-C ratio, which was significantly lower in patients with stenosis. Our results indicate that the ratio of ubiquinol-10/LDL-C is likely to be a risk factor for atherogenesis.

Influence of coenzyme Q(10) and cerivastatin on the flow-mediated vasodilation of the brachial artery: results of the ENDOTACT study

AIM

Endothelial dysfunction (ED) is the functional prestep in atherosclerosis. Aim of the present study was to evaluate the effects of a potent antioxidant (coenzyme Q(10), CoQ(10)) and of cerivastatin on ED of the brachial artery.

METHODS AND RESULTS

Twenty-five male patients with manifest ED (flow-mediated vasodilation [FMD%]<4.5%) were included in this prospective, randomized, cross-over study. ED of the brachial artery was assessed by the use of high-resolution ultrasound. Each patient had to pass through three treatment phases ((1) single therapy with cerivastatin (C), (2) single therapy with CoQ(10), (3) combination therapy). FMD% significantly improved throughout all treatment phases ((1) 3.50+/-4.05% vs. 8.80+/-6.39%, p=0.009; (2) -0.25+/-4.0% vs. 7.06%+/-4.39%, p=0.004; (3) 3.14+/-3.54% vs. 8.82+/-5.78%, p=0.011). C led to a significant decrease of CoQ(10) plasma levels (1.23+/-0.34 vs. 0.87+/-0.39 microg/ml, p=0.004).

CONCLUSION

Our results indicate a positive influence of CoQ(10) supplementation on human ED, which appears to be independent of lipid lowering. Although large-scale studies evaluating other antioxidants failed to demonstrate a positive prognostic effect, Q(10) has never been evaluated in larger trials. Experimental as well as clinical results indicate that CoQ(10) warrants further attention in atherosclerosis research.

Sensitive and selective analysis of coenzyme Q10in human serum by negative APCI LC-MS

Two new sensitive and selective LC-MS methods have been developed for the quantification of the total coenzyme Q(10) concentration in human blood serum. The sensitivity of the methods is based on the very efficient formation of the radical anions of CoQ(10)[M(-)[radical dot]] by negative atmospheric pressure ionisation, APCI(-). The mass detection of the [M(-)[radical dot]] ions, m/z= 862.6, was performed either in selective ion monitoring (SIM) or in MS(2) mode (m/z= 862.6 [rightward arrow]m/z= 847.6) using an LCQ-deca ion-trap mass spectrometer. Two standard serum samples with medium (0.73 [micro sign]g ml(-1)) and high (1.96 [micro sign]g ml(-1)) total CoQ(10) concentrations were analysed by LC-APCI(-)-SIM and LC-APCI(-)-MS(2) and the results compared with a HPLC literature procedure with electrochemical detection (ECD). Both the LC-MS methods were shown to be more selective and with comparable or better sensitivity than the HPLC-ECD method. The LC-MS-SIM and LC-MS(2) chromatograms of the medium concentration sample showed CoQ(10) signal to noise ratios of 25 and 625, respectively. In addition, a simple and fast serum pre-treatment procedure was developed, in which the serum CoQ(10)H(2) content was quantitatively oxidised quantitatively to CoQ(10) in less than 15 min by 1,4-benzoquinone.

Total coenzyme Q10 concentrations in Asian men following multiple oral 50-mg doses administered as coenzyme Q10 sustained release tablets or regular tablets

Coenzyme Q(10) (CoQ(10)), a highly lipophilic compound present in the inner mitochondrial membrane, is essential for production of cellular energy in the form of ATP. CoQ(10) is used as a dietary supplement and for treatment of various cardiovascular disorders. Our goal was to compare the CoQ(10) levels in Asians following multiple oral doses administered as sustained release or regular tablets. Twenty healthy male volunteers (19-23 years old) were divided into two equal groups. Each subject in Group I received 50 mg oral doses of coenzyme Q(10) as sustained release tablets once a day for fifteen days, while subject in Group II received 50 mg doses of coenzyme Q(10) regular tablets. The CoQ(10) levels were measured by HPLC-UV (reverse phase ODS column, 10 microm, 250 x 4.6 mm; oven temperature 30 degrees C). Mobile phase was constituted by methanol-ethanol 9 : 1 v/v. Flow rate was 1.5 ml/min and UV detection was carried out at 275 nm. Coenzyme Q(9) was used as an internal standard. CoQ(10) baseline in the morning was 0.88+/-0.48 mg/l. Following 1 week 50 mg/d dosing of CoQ(10), plasma CoQ(10) concentrations increased to 1.85+/-1.03 mg/l for sustained release tablets and up to 1.37+/-0.74mg/l for regular tablets. The net increment proportion in AUC for sustained release and regular tablets were 148.26+/-176.56%, 102.57+/-130.00%, respectively. Both preparations significantly increased the systemic exposure when compared to endogenous baseline.

Anticoagulant effects on plasma coenzyme Q(10) estimated by HPLC with coulometric detection

BACKGROUND

The proportion of reduced coenzyme Q(10) (Q(10)H(2)) in total coenzyme Q(10) (TQ(10)), referred to as the Q(10)H(2):TQ(10) ratio, may be used as a possible marker of in vivo oxidative stress. However, the ranges for Q(10)H(2):TQ(10) ratio from previous reports are quite variable. Sample handling and preparation appear to have a profound effect on the stability of Q(10)H(2).

METHODS

Paired tests were used to estimate TQ(10), Q(10)H(2), oxidized coenzyme Q(10) (Q(10)), and Q(10)H(2):TQ(10) ratio in patient samples collected in vacutainers containing heparin or EDTA. Sample tubes were immediately placed on ice and promptly centrifuged. After harvesting plasma, 100 microl of plasma was extracted with 1-propanol and centrifuged. The supernatant was injected directly into a high-performance liquid chromatography (HPLC) system.

RESULTS

Significantly higher values (p=0.0015) of TQ(10), Q(10)H(2), and Q(10)H(2):TQ(10) ratio were noted in heparinized plasma as compared to EDTA plasma; Q(10) concentrations were lower in heparinized plasma. When vacutainers containing specimen were opened and kept refrigerated, the Q(10)H(2):TQ(10) ratios in heparinized samples were stable over 7 h with variation <3%. Blood Q(10)H(2) in closed heparin vacutainers kept refrigerated was stable up to 24 h.

CONCLUSIONS

Our results indicate that the heparinized plasma is superior to the EDTA plasma in all measurements for coenzyme Q(10).

HPLC Analysis of Reduced and Oxidized Coenzyme Q10 in Human Plasma

Background: The percentage of reduced coenzyme Q10 (CoQ10H2) in total coenzyme Q10 (TQ10) is decreased in plasma of patients with prematurity, hyperlipidemia, and liver disease. CoQ10H2 is, however, easily oxidized and difficult to measure, and therefore reliable quantification of plasma CoQ10H2 is of clinical importance.

Methods: Venous blood was collected into evacuated tubes containing heparin, which were immediately placed on ice and promptly centrifuged at 4 °C. The plasma was harvested and stored in screw-top polypropylene tubes at −80 °C until analysis. After extraction with 1-propanol and centrifugation, the supernatant was injected directly into an HPLC system with coulometric detection.

Results: The in-line reduction procedure permitted transformation of CoQ10 into CoQ10H2 and avoided artifactual oxidation of CoQ10H2. The electrochemical reduction yielded 99% CoQ10H2. Only 100 μL of plasma was required to simultaneously measure CoQ10H2 and CoQ10 over an analytical range of 10 μg/L to 4 mg/L. Intra- and interassay CVs for CoQ10 in human plasma were 1.2–4.9% across this range. Analytical recoveries were 95.8–101.0%. The percentage of CoQ10H2 in TQ10 was ∼96% in apparently healthy individuals. The method allowed analysis of up to 40 samples within an 8-h period.

Conclusions: This optimized method for CoQ10H2 analysis provides rapid and precise results with the potential for high throughput. This method is specific and sufficiently sensitive for use in both clinical and research laboratories.