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img oxidative 5We offer various analytical testing services. Enquiries can be sent to Prof Marnewick at

Total Antioxidant Capacity

  • Oxygen radical absorbance capacity (ORAC): A fluorescence method that is based on the finding that the fluorescence of fluorescein (FL) changes with respect to time upon damage caused by peroxyl or hydroxyl radical attack. The ORAC method was also adapted to be able to analyse the lipid-soluble antioxidant samples.
  • Ferric reducing antioxidant power assay (FRAP): The FRAP assay gives fast, reproducible results with a wide variety of biological and food samples. The FRAP assay uses an oxidation/reduction reaction to measure the ability of a sample to reduce iron(III) to iron(II).
  • Trolox equivalent antioxidant capacity (TEAC): The TEAC assay uses the 2,2-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) radical cation (ABTS•+). It has been applied in beverages and foods as well as in biological fluids. The assay is applicable to both hydrophilic and lipophilic environments.

Individual compounds (HPLC)

  • Carotenoids (carotenes,lutein, lycopene)
  • Resveratrol
  • Ascorbic acid (vitamin C)
  • Epicatechin, epicatechin gallate, epigallocatechin, epigallocatechin gallate, catechin, gallocatechin, gallocatechin gallate, and catechin gallate.
  • Quercetin, kaempferol, apigenin, luteolin, rutin, isoquercitrin, aspalathin
  • Vitamin E (tocopherols; tocotrienols)

Antioxidants and/or enzymes

  • Superoxide dismutase (SOD): SOD’s are metalloenzymes that catalyse the dismutation of the superoxide anion to molecular oxygen and hydrogen peroxide and thus form an important part of the cellular antioxidant defence mechanism. Total SOD activity (cytosolic and mitochondrial) or only cytosolic or mitochondrial SOD activity can be determined.
  • Catalase (CAT): Catalase is a ubiquitous antioxidant enzyme that is present in most aerobic cells.
  • Glutathione reductase (GR): Glutathione reductase is a flavoprotein that catalyses the NADPH-dependent reduction of oxidised glutathione (GSSG) to GSH. This enzyme is essential for the GSH redox cycle, which maintains adequate levels of reduced cellular GSH.
  • Glutathione peroxidase (GPx): Glutathione peroxidase catalyses the reduction of hydroperoxides, including hydrogen peroxide, by reduced glutathione and functions to protect the cell from oxidative damage.
  • GSH/GSSG ratio: Glutathione is a tripeptide widely distributed in both plants and animals. Increased oxidative stress in a cell, causes the ratio of GSH:GSSG (reduced to oxidised glutathione) to decrease, mostly because of the accumulation of GSSG, but also because of an increased reduced glutathione level. This ratio is used as an indicator of oxidative stress in a biological system and may also be used to monitor various antioxidant interventions.

Total groups (spectrophotometric)

  • Carotenoids
  • Polyphenols
  • Flavonols (Traditional rooibos tea contains a variety of flavonols such as rutin and isoquercitrin, all contributing to the antioxidant activity of rooibos tea.)
  • Flavanols (catechins) (Green tea as well as black tea contains various polyphenolic compounds (flavan-3ols) generally known as catechins. Pharmacological functions of catechins have been studied, including protection against coronary heart disease, various types of cancer and inflammatory disease.)
  • Anthocyanins