Total antioxidant capacity reduction assays

Various Reduction Assays of Total Antioxidant Capacity ... 

Prieto et al. (1999) reported another spectrophotometric method for the quantitative determination of antioxidant capacity based on the reduction of Mo(VI) to Mo(V) by vitamin E in acidic conditions with incubation at 95°C for 90 min. The subsequent green phosphate/Mo(V) complex, after cooling at room temperature was monitored at 695 nm with a calibration range of 0.2-2 x 10 M (r = 0.997) and a detection limit of 0.135 pmol vitamin E. The method was applied for measurement of total antioxidant capacity of plant extracts and to determine vitamin E in a variety of grains and seeds, including corn and soybean. The recovery of vitamin E from seeds was determined by supplementing the samples with the different vitamin E isomers or a-tocopherol acetate as internal standard and applying both the proposed method and a standard HPEC assay (Huo et al., 1996) and yielded a recovery of 93%-97% tocopherols. 

A spectrophotometric method based on reduction of Mo(VI) to Mo(V) has been developed for the quantitative determination of the total antioxidant capacity of hexane extracts of com and soybean samples (Prieto et al., 1999). The antioxidant activity of methanohc corncobs extracts was measured based on their ability to scavenge the DPPH (2,2-diphenyl-l-picrylhydrazyl) radical (Sultana et al., 2007). This assay is based on radical disappearance according with sample antioxidant capacity (Figure 10). 

The on-line measurement of reducing capacity can be performed with either a single or a series of electrochemical detectors, and linear correlations have been demonstrated between total antioxidative activities determined by the electrochemical detection and those determined by DPPH- reduction or by the ORAC assay (Guo et al, 1997 Peyrat-Maillard et al, 2000). The reducing capacity must also be quantified by post-column reactions, either with DPPH- or by the reduction of phosphomolybdenum complexes followed by UV-VIS-detection (Bandoniene and Murkovic, 2002 Cardenosa et al, 2002). A combination of HPLC and semi-automatic ORAC analysis has also been described (Caldwell, 2001). 

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