In Vitro Screening of Antioxidant Substances by Fading Spectrophotometric

A simple method for the determination of hydroxyl radical was established to screen the antioxidant substances and evaluate their antioxidation ability. In this paper, effect of pH on absorption spectrum of dyes, the optimal experimental condition of the fading reaction, the kinetics of degradation of dyes by Fenton oxidation, the relationship between the molecular structure of dyes and reaction rate, effect of co-existing ions on the reaction were investigated. Results indicate that the absorption spectrum of dyes do not shift and the position of absorption peak keep stable when the pH value is higher than 3. The apparent molar absorptivity of VPB BO is 50000L/ (mol·cm), which is the highest among the seven dyes. MB, Rh B, VPB BO, VPB B, VPB R, NB and MG are decrease of reaction rate. This method was successfully employed to measure the antioxidant activities of three substances, four vegetable extract and four fruit extract.