Yen Lin Chang

Ascorbate Supplement Reduces Oxidative Stress in Dyslipidemic Patients Undergoing Apheresis

Objective—The effect of ascorbate treatment on apheresis-induced oxidative stress in uremic and dyslipidemic patients was evaluated. Methods and Results—We developed a chemiluminescence-emission spectrum and high-performance liquid chromatography analysis to assess the effect of ascorbate supplement on plasma reactive oxygen species (ROS) scavenging activity and oxidized lipid/protein production in hyperlipidemic and uremic patients undergoing apheresis. Apheresis was efficient in reduction of atherogenic lipoproteins, complement, fibrinogen, soluble intercellular adhesion molecule-1, and oxidative parameters including phosphatidylcholine hydroperoxide (PCOOH), malonaldehyde, methylguanidine, and diotyrosine. Apheresis itself, however, activated leukocytes to increase ROS activity and reduced the plasma ROS scavenging activity. Ascorbate administration selectively diminished apheresis-enhanced H2O2 and inflammatory mediators such as tumor necrosis factor alpha (TNF-&agr;) and monocyte chemoattractant protein-1. Chronically dyslipidemic and uremic patients undergoing biweekly apheresis plus ascorbate treatment had lower levels of C-reactive protein and PCOOH than did those without ascorbate treatment during a 6-month follow-up study period. Conclusions—We demonstrate that apheresis with ascorbate treatment provides a therapeutic potential in reducing atherosclerotic risk via inhibition of H2O2-induced oxidative stress in patients with uremia or dyslipidemia.

New analytical method for investigating the antioxidant power of food extracts on the basis of their electron-donating ability: comparison to the ferric reducing/antioxidant power (FRAP) assay.

Several analytical approaches are available for investigating the antioxidant power for antioxidants, and they are based on a variety of chemical principles, such as oxygen radical absorbance capacity (ORAC), Trolox equivalent antioxidant capacity (TEAC), and ferric reducing/antioxidant power (FRAP). This paper reports a new rapid method for investigating antioxidant power on the basis of the electron-donating ability. This method is called chemiluminescence analysis of antioxidant power (CAAP). The electrons donated from antioxidants are capable of inducing chemiluminescence in the presence of lucigenin and a base. Thus, the intensity of chemiluminescence induced by antioxidants is proportional to their electron-donating ability (antioxidant power). It was found that the correlation between CAAP and FRAP was positive (r = 0.959) and statistically significant (p < 0.05). In addition to the FRAP assay, the rapid CAAP assay is convenient for investigating the antioxidant power of herbal extracts.

Efficacy of Epigallocatechin-3-Gallate and Amla (Emblica officinalis) Extract for the Treatment of Diabetic-Uremic Patients

Uremic patients with diabetes suffer from high levels of oxidative stress due to regular hemodialysis therapy (neutrophil activation induced by hemo-incompatibility between the hemodialyser and blood) and complications associated with diabetes. Several plasma biomarkers were screened in 13 uremic diabetic patients after receiving the mixture of (-)-epigallocatechin gallate (EGCG), a major component of green tea extract, and Amla extract (AE), from Emblica officinalis, the Indian gooseberry, for 3 months. We found that oral administration of a 1:1 mixture of EGCG and AE for 3 months significantly improved antioxidant defense as well as diabetic and atherogenic indices in uremic patients with diabetes. Furthermore, no significant changes in hepatic function, renal function, or inflammatory responses were observed. These results suggest that a 1:1 combination of EGCG and AE is a safe and effective treatment for uremic patients with diabetes.

The application of (-)-epigallocatechin gallate in preparation of an antioxidant dialysate.

Hemodialysis can remove uremic solutes but this treatment induces oxidative stress in uremic patients because of hemo-incompatibility. Therefore, we hypothesised that an antioxidant dialysate (a dialysate containing antioxidant(s)) would provide antioxidant defence in uremic patients during hemodialysis. Several herbal extracts were studied and measurements of antioxidant power and stability assays indicated that epigallocatechin gallate (EGCG) was the best of those tested for use as an antioxidant dialysate (EGCG dialysate). We observed that EGCG dialysate could provide the highest level of antioxidant defence at a dialysate flow rate of 500 ml/min and a blood flow rate of 200 ml/min. In addition, some important parameters for hemodialysis were calculated for supporting the protective role of EGCG dialysate. This is the first description of the preparation of an antioxidant dialysate. We suggest that EGCG dialysate will reduce the level of oxidative stress in hemodialysis patients, leading to a decrease of complications associated with oxidative damage.

Chemiluminescence analysis of antioxidant capacity for serum albumin isolated from healthy or uremic volunteers.

Regular hemodialysis treatment induces an elevation in oxidative stress in patients with end-stage renal failure, resulting in oxidative damage of the most abundant serum protein, albumin. Oxidation of serum albumin causes depletion of albumin reactive thiols, leading to oxidative modification of serum albumin. The aim of this study was to screen the antioxidant capacity of albumins isolated from uremic patients (HD-ALB) or healthy volunteers (N-ALB). From high-performance liquid chromatography spectra, we observed that one uremic solute binds to HD-ALB via the formation of disulfide bonds between HD-ALB and the uremic solute. Furthermore, we found using chemiluminescent analysis that the antioxidant capacities for N-ALB to scavenge reactive oxygen species including singlet oxygen, hypochlorite and hydrogen peroxide were higher than HD-ALB. Our results suggest that protein-bound uremic solute binds to albumin via formation of disulfide bonds, resulting in the depletion of albumin reactive thiols. The depletion of albumin reactive thiols leads to a reduced antioxidant capacity of HD-ALB, implying postmodification of albumin. This situation may reduce the antioxidant capacity of albumin and increase oxidative stress, resulting in increase in complications related to oxidative damage in uremic patients. Copyright

Rapid method for the quantification of hydroquinone concentration: chemiluminescent analysis

Topical hydroquinone serves as a skin whitener and is usually available in cosmetics or on prescription based on the hydroquinone concentration. Quantification of hydroquinone content therefore becomes an important issue in topical agents. High-performance liquid chromatography (HPLC) is the commonest method for determining hydroquinone content in topical agents, but this method is time-consuming and uses many solvents that can become an environmental issue. We report a rapid method for quantifying hydroquinone content by chemiluminescent analysis. Hydroquinone induces the production of hydrogen peroxide in the presence of basic compounds. Hydrogen peroxide induced by hydroquinone oxidized light-emitting materials such as lucigenin, resulted in the production of ultra-weak chemiluminescence that was detected by a chemiluminescence analyzer. The intensity of the chemiluminescence was found to be proportional to the hydroquinone concentration. We suggest that the rapid (measurement time, 60 s) and virtually solvent-free (solvent volume, <2 mL) chemiluminescent method described here for quantifying hydroquinone content may be an alternative to HPLC analysis.