Spectrophotometric quantitation of antioxidant capacity through the formation of a phosphomolybdenum complex: Specific application to the determination of vitamin E

A spectrophotometric method has been developed for the quantitative determi nation of antioxidant capacity. The assay is based on the reduction of Mo(V I) to Mo(V) by the sample analyte and the subsequent formation of a green p hosphate/Mo(V) complex at acidic pH. The method has been optimized and char acterized with respect to linearity interval, repetitivity and reproducibil ity, and molar absorption coefficients for the quantitation of several anti oxidants, including vitamin E. The phosphomolybdenum method, in combination with hexane monophasic extraction, has also been adapted for the specific determination of vitamin E in seeds. The results obtained with the proposed method were validated by comparison with a standard HPLC method. The phosp homolybdenum method is routinely applied in our laboratory to evaluate the total antioxidant capacity of plant extracts and to determine vitamin E in a variety of grains and seeds, including corn and soybean. (C) 1999 Academi c Press.