Comparision of antioxidant capacity in urine by ORAC analysis after consumption of muscadine grape juice

Antioxidant capacity (AC) is a measure of the potential of antioxidants to suppress oxidative damage. Muscadine grapes are a rich source of antioxidants such as: resveratrol, polyphenols, and vitamin C. Objective To measure the change in urinary AC of subjects before and after consuming muscadine grape juice. Methods 10 subjects were recruited by the snow‐ball effect to provide 10 days of first‐void urine measured as baseline controls followed by another 10 days of first‐void urine when grape juice was consumed each preceding night. Baseline samples were used to determine the individual variation in AC prior to juice consumption. This was compared to urinary AC following daily and cumulative juice consumption. The Oxygen Radical Absorbance Capacity (ORAC) assay, modified for urine samples, was used to measure AC in urine. Results The mean and average %SD of baseline samples was 213 μmol TE/ml ± 3.9%SD. ORAC values were measured in urines following juice consumption and consumption over time. Results for baseline samples revealed substantial inter‐individual variability. The post‐consumption ORAC results will indicate if muscadine grapes are an absorbable and measurable source of antioxidants.