Colored thin film for screening and evaluation of antioxidants

Colored thin film was prepared by embedding violet colored stable free radical, 2,2-Diphenyl-1-picrylhydrazyl (DPPH) in a polyvinyl alcohol (PVA) thin film. The radical scavenging activity was assessed on the basis that the absorbance value of the colored thin film reduced on immersing the thin film in methanol containing antioxidant compared to that in the absence of antioxidant. Ascorbic acid and α-tocopherol were used as standard antioxidants for the assay. The radical scavenging activities of these two antioxidants were found to have linear correlation with the concentrations of the antioxidants. Orchid flower extract, curcumin and gallic acid were also found to have radical scavenging activity using this colored thin film. The results demonstrated that the PVA-DPPH colored thin film provides a simple, economical, rapid method for screening as well as quantitative assessment of radical scavenging activity of antioxidants in plant extracts, bioactive molecules from plant extract and organic compounds.