Free-radical scavenging capacity using the fenton reaction with rhodamine B as the spectrophotometric indicator.

A spectrophotometric method was developed to measure antioxidant free-radical scavenging capacity. Rhodamine B (RhB) was oxidized by hydroxyl radical generated via the Fenton reaction to yield a photoinactive RhB product. RhB absorption at 550 nm was restored when antioxidant agents scavenged hydroxyl radical to protect RhB from oxidation. On the basis of the dose response of antioxidant recovery capacity, a model was developed to calculate the free-radical scavenging ability. This method was sensitive to a wide range of antioxidant activity with ascorbic acid reference set as one; the antioxidant recovery capacity of quercetin was 635 compared to 2 for benzoic acid.