<Tr> <Td> Ubiquinol (coenzyme Q) </Td> <Td> Lipid </Td> <Td> 5 </Td> <Td> 200 (human) </Td> </Tr> <P> Uric acid is by far the highest concentration antioxidant in human blood . Uric acid (UA) is an antioxidant oxypurine produced from xanthine by the enzyme xanthine oxidase, and is an intermediate product of purine metabolism . In almost all land animals, urate oxidase further catalyzes the oxidation of uric acid to allantoin, but in humans and most higher primates, the urate oxidase gene is nonfunctional, so that UA is not further broken down . The evolutionary reasons for this loss of urate conversion to allantoin remain the topic of active speculation . The antioxidant effects of uric acid have led researchers to suggest this mutation was beneficial to early primates and humans . Studies of high altitude acclimatization support the hypothesis that urate acts as an antioxidant by mitigating the oxidative stress caused by high - altitude hypoxia . </P> <P> Uric acid has the highest concentration of any blood antioxidant and provides over half of the total antioxidant capacity of human serum . Uric acid's antioxidant activities are also complex, given that it does not react with some oxidants, such as superoxide, but does act against peroxynitrite, peroxides, and hypochlorous acid . Concerns over elevated UA's contribution to gout must be considered as one of many risk factors . By itself, UA - related risk of gout at high levels (415--530 μmol / L) is only 0.5% per year with an increase to 4.5% per year at UA supersaturation levels (535 + μmol / L). Many of these aforementioned studies determined UA's antioxidant actions within normal physiological levels, and some found antioxidant activity at levels as high as 285 μmol / L . </P> <P> Ascorbic acid or "vitamin C" is a monosaccharide oxidation - reduction (redox) catalyst found in both animals and plants . As one of the enzymes needed to make ascorbic acid has been lost by mutation during primate evolution, humans must obtain it from the diet; it is therefore a vitamin . Most other animals are able to produce this compound in their bodies and do not require it in their diets . Ascorbic acid is required for the conversion of the procollagen to collagen by oxidizing proline residues to hydroxyproline . In other cells, it is maintained in its reduced form by reaction with glutathione, which can be catalysed by protein disulfide isomerase and glutaredoxins . Ascorbic acid is a redox catalyst which can reduce, and thereby neutralize, reactive oxygen species such as hydrogen peroxide . In addition to its direct antioxidant effects, ascorbic acid is also a substrate for the redox enzyme ascorbate peroxidase, a function that is particularly important in stress resistance in plants . Ascorbic acid is present at high levels in all parts of plants and can reach concentrations of 20 millimolar in chloroplasts . </P>

Which of the following is used as an antioxidant in the processing of food