Simple scanometric assay based on DPPH immobilized on pharmaceutical blister for determination of antioxidant capacity in the herbal extracts

Abstract

A simple scanometric assay for antioxidant capacity of the herbal extracts has been developed based on dry reagent of 2,2-diphenyl-1-picrylhydrazyl (DPPH) immobilized on the pharmaceutical blister. The deep violet color of DPPH solution was regenerated by introducing methanol to each well as sensing zones. The antioxidant capacity of plant extract will proportionally reduce the violet color to form the corresponding yellow color adduct, where the color change was captured by a flatbed scanner. Then, the optical responses toward antioxidant are presented as an averaged value of the red green blue (RGB) color using image color analysis (ImageJ). By using this color value, analytical performance of the antioxidant sensor could be characterized, where it has a linear range between 1-28 mg/L as gallic acid equivalent (GAE), with response time at 10 min. The reproducibility of the antioxidant sensor was good (RSD < 1%) with the recovery value of 102-105%. The scanometric assay was applied to several herbal extracts, such as sappan wood, guava leaf, and turmeric rhizome. The results obtained are in good agreement with the spectrophotometric method, suggesting that the proposed assay can be used as an alternative method for antioxidant capacity determination.