Abstract This article reviews literatures concerning preparation of stable free radical DPPH (22-diphenyl-1-picrylhydrazyl) and its derivatives. The key intermediate playing an important role is diarylhydrazine. The article reports solution methods for problems in each step of the reaction. In addition it also shows the development of DPPH synthesis and other stable free radical DPPH derivatives besides DPPH

A novel and simple method for measuring total antioxidant capacity or T AC in Thai herb extracts has been developed. The principle is based on generating free radical the deep blue Imipramine radical is generated by oxidizing Imipramine by ammonium tetravanadate in acid medium that can be easily scavenged by antioxidant compounds in the sample. Decreasing in the absorption spectrum at 620 nm related with antioxidant capacity was detected by spectrophotometer method in the proposed of practicable and low-cost However improvement of the throughput Flow injection analysis (FIA) was applied. The variables affecting the signal such as pH reagent concentrations linear relationship was optimized. The novel assay is linear up to 2800 mg Trolox equivalent/L its precision value is lower than 1% RSD and these are no interference from NaOH NaCI and N~C03 The method was applied for determination of three extract fractions of G. sootepensis. The results show the different of antioxidant capacity in each fraction with S I has the most TAC following S2 and S3 respectively. Although a good correlation of the present method was observed between two methods DPPH and Follin Ciocalteu reagent Finally the developed method was easy stable inexpensive environmental friendly and automated measures total antioxidant capacity.