Antioxidant Assays

Reactive oxygen species (ROS) play a critical role in cellular physiopathology and are implicated for example in cell proliferation, cell signaling pathways, homeostasis, apoptosis, thyroid hormon synthesis, as well as oxidative defense mechanisms (e.g. killing of bacteria). In several disorders such as cancer or neurodegenerative and cardiovascular diseases, the redox balance is disturbed and excessive amounts of ROS can can lead to cellular injury by damaging cellular structures, proteins, membrane lipids and DNA, which is known as oxidative stress.
Excess ROS must be promptly eliminated from the cell by a variety of antioxidant defense mechanisms. ROS generation is normally counterbalanced by the action of cellular antioxidant enzymes and other redox molecules such Superoxide Dismutase (SOD), Catalases or glutathione (GSH).

Antioxidants have an overall capability to counteract reactive oxygen species (ROS), resist oxidative damage and combat oxidative stress-related Thus, they play an important role in preventing the formation of and scavenging of free radicals and other potentially toxic oxidizing species. There are three categories of antioxidant species: enzyme systems (GSH reductase, thioredoxin reductase, catalase, peroxidase, etc.), small molecules (ascorbate, uric acid, GSH, vitamin E, etc.) and proteins (albumin, transferrin, etc.). Different antioxidants vary in their reducing power. an indication of the  In some cases, the antioxidant contribution of proteins is desired whereas in other cases only the contribution of the small molecule antioxidants is needed.

Total Antioxidant Capacity (TAC) Assay Kit

PromoKine’s Total Antioxidant Capacity (TAC) Assay Kit is a colorimetric assay that is based on copper reduction by antioxidants.  It measure either the combination of both small molecule antioxidants and proteins or small molecules alone in the presence of a proprietary Protein Mask. In the presence of antioxidants, the Cu2+ ion is converted to Cu+ (by both small molecules and proteins). However, the Protein Mask prevents Cu2+ reduction by proteins, enabling the analysis of only the small molecule antioxidants. The reduced Cu+ ion is chelated with a colorimetric probe giving a broad absorbance peak around 570 nm, proportional to the total antioxidant capacity.

SOD Assay Kit

Superoxide dismutase (SOD) is one of the most important antioxidative enzymes. The highly sensitive SOD Assay Kit utilizes WST-1 that produces a water-soluble formazan dye upon reduction with the superoxide anion. The rate of the reduction with a superoxide anion is linearly related to the xanthine oxidase (XOD) activity, and is inhibited by SOD. Therefore, the inhibition activity of SOD can be determined by a colorimetric method.

Principle of the SOD Assay Kit.

Catalase Activity Assay Kit

Catalase is a ubiquitous antioxidant enzyme that is present in nearly all living organisms. It functions to catalyze the decomposition of hydrogen peroxide (H₂O₂) formed during oxidative stress to water and oxygen.

PromoKine’s Catalase Activity Assay Kit provides a simple, direct, HTS-ready and highly sensitive assay for measuring Catalase activity in various biological samples (detecting pico-units of catalase). In the assay, catalase first reacts with H₂O₂ to produce water and Oxygen. The unconverted H₂O₂ then reacts with OxiRed probe to generate a product, which can be measured at 570 nm (colorimetric method) or at Ex/Em=535/587nm (fluorometric method). Catalase activity is reversely proportional to the signal. 

Ascorbic Acid Assay Kit

Ascorbic Acid (Vitamin C) is a water-soluble antioxidant found in living organisms. It plays an important role in many biological processes and is a potent anti-oxidant, anti-inflammatory, and anti-viral agent, also having an effect as immune stimulant. It is critical for a variety of functions related to tissue growth and wound healing, neurotransmitter formation, blood cholesterol levels, as well as free radical neutralization. Being present in a wide variety of foods and biological specimens, it is important to be able to monitor variations of the ascorbic acid content reliably and accurate.

PromoKine’s Ascorbic Acid Assay Kit provides a rapid, simple and sensitive method of detecting ascorbic acid in various biological samples. In this assay, a proprietary catalyst oxidizes ascorbic acid to a product that interacts with the ascorbic acid probe, generating a colorimetric (at λ = 570 nm) as well as fluorometric (Ex/Em = 535/587 nm) signal. The assay can detect 0.01-10 nmol of ascorbic acid per assay in various samples.

Gamma Glutamyl Transferase (GGT) Activity Assay Kits

Gamma-glutamyltransferase (GGT) plays a key role in the synthesis of the antioxidant glutathione and thus in drug and xenobiotic detoxification. As part of glutathione recycling, it catalyzes the transfer of gamma-glutamyl functional groups from molecules such as glutathione to an acceptor that may be an amino acid, a peptide or water (forming glutamate). GGT is found in cell membranes of many tissues mainly in the liver, kidney, and pancreas. It is a diagnostic marker for various disorders that has traditionally been measured to detect liver health. High GGT levels have also been linked to increased risk of cancer, diabetes or cardiovascular mortality.

PromoKine's Gamma Glutamyl Transferase (GGT) Activity Assay Kits provide convenient tools for sensitive quantification of GGT activity in a variety of samples, either colorimetrically (λ = 418 nm) or fluorometrically (Ex/Em = 365/460 nm).

Thioredoxin Reductase Activity Assay & Inhibitor Screening Kits

The thioredoxin (Trx) system, which is composed of thioredoxin reductase (TrxR), thioredoxin and NADPH,  is a key antioxidant system in defense against oxidative stress. Thioredoxin reductase (TrxR) is a ubiquitous enzyme which is also involved in many other cellular processes such as cell growth, p53 activity, cancer, immune response and viral infection.

PromoKine's Thioredoxin Reductase Activity Assay Kit provides a convenient colorimetric assay for detecting TrxR activity in various samples. In the assay TrxR catalyzes the reduction of 5, 5’-dithiobis (2-nitrobenzoic) acid (DTNB) with NADPH to 5-thio-2-nitrobenzoic acid (TNB2-), generating a strong yellow color (λmax = 412 nm). In crude biological samples, other enzymes such as glutathione reductase and glutathione peroxidase can also reduce DTNB. Therefore, a TrxR specific inhibitor is utilized to determine TrxR-specific activity and two assays are performed: The first measurement quantifies the total DTNB reduction by the sample, and the second one measures the DTNB reduction by the sample in the presence of the TrxR-specific inhibitor. The difference between the two results is the DTNB reduction by TrxR.

PromoKine's Thioredoxin-1 (Trx1) Inhibitor Screening Kit provides a fast, convenient and high throughput-adaptable method to screen for Trx1 Inhibitors. In this assay, Trx1 reduces a quenched di-FITC-labeled, oxidized glutathione (Trx1 substrate), to mono-FITC-labeled unquenched, reduced glutathione. In the presence of a a Trx1 inhibitor (control inhibitor is included in the kit), the reaction is impeded or abolished, resulting in lower or no signal.

References, Questions & Answers

Product Name Description Size Catalog Number Information Prices
Total Antioxidant Capacity (TAC) Assay Kit Colorimetric measurement of the combined nonenzymatic antioxidant capacity of biological fluids and other samples 100 assays PK-CA577-K274 click to select country
SOD Assay Kit Kit contains for convenient measurement of activity of Superoxide Dismutase (SOD) by colorimetric method 100 assays PK-CA577-K335 click to select country
Catalase Activity Assay Kit Highly sensitive, simple, direct and HTS-ready colorimetric & fluorometric assay for measuring catalase activity in biological samples 100 assays PK-CA577-K773 click to select country
Ascorbic Acid Assay Kit Rapid, simple, and sensitive assay for colorimetric & fluorometric detection of ascorbic acid in various biological samples 100 assays PK-CA577-K661 click to select country
Gamma Glutamyl Transferase (GGT) Activity Assay Kit I Convenient kit for sensitive and high-throughput adaptable colorimetric determination of the GGT level in a variety of samples 100 assays PK-CA577-K784 click to select country
Gamma Glutamyl Transferase (GGT) Activity Assay Kit II Convenient kit for sensitive and high-throughput adaptable fluorometric determination of the GGT level in a variety of samples 100 assays PK-CA577-K785 click to select country
Thioredoxin Reductase Activity Assay Kit Kit provides a convenient, fast and simple colorimetric assay for detecting TrxR activity in various samples 100 assays PK-CA577-K763 click to select country
Thioredoxin-1 (Trx1) Inhibitor Screening Kit Fluorometric assay for rapid, simple, sensitive and high-throughput adaptable screening/studying/characterizing Thioredoxin-1 inhibitors 100 assays PK-CA577-K535 click to select country
Superoxide Dismutase (SOD, human) Recombinant human Superoxide Dismutase 100 µg PK-RP577-4802-100 click to select country
L-Ascorbic acid L-Threoascorbic acid, Antiscorbutic factor, Vitamin C 100 mg PK-CA577-2269-100 click to select country
L-Ascorbic acid L-Threoascorbic acid, Antiscorbutic factor, Vitamin C 1 g PK-CA577-2269-1000 click to select country