Determination of antioxidant activity of some drugs using high-pressure liquid chromatography.

The antioxidant activities of different drugs like acetylsalicylic acid, nimesulide, dapsone, methlydopa, rifampicin and the well known antioxidants ascorbic acid and quercetin were assessed using the stable free radical alpha,alpha-diphenyl-beta-picrylhydrazyl (DPPH). DPPH is easily soluble at lower concentrations in methanol. It has a deep violet color. The changes in color are monitored calorimetrically. The measurements were made using HPLC at wavelengths 256 nm and 517 nm. The interactions between different drugs with DPPH were studied. All the compounds tested reduced DPPH. This method can be used to investigate oxygen free radical scavenging activity of drug candidates.