An amended potassium persulfate ABTS antioxidant assay used for medicinal plant extracts revealed antioxidant variation based upon plant extraction process

Use of potassium persulfate (K2S208) for oxidation of 7.0 mM ABTS to a stable ABTS radical for antioxidant studies was first reported in 1999. A feature of this popular antioxidant assay has been the requirement of an overnight reaction (6 to 12 h) for the formation of a stable ABTS colored radical. It is now reported that when the concentration of ABTS is lowered to 0.7 mM, complete oxidation to the stable cation radical occurs in 30 min, thus circumventing the necessary overnight step. Using this format, it is now possible to accurately assess antioxidant activity based on the potassium persulfate/ABTS format in less than one hour which includes formation time of a stable ABTS radical. This methodology documented the presence of antioxidant properties of plant extracts used in Traditional Chinese Medicine. The degree of antioxidant activity was directly related to the extraction method. Greater antioxidant activity was associated with butanol extraction. When incorporated into a microtiter plate format, it supported rapid assessment of multiple determinations of dilutions of plant extracts in less than one hour which included time required for formation of a stable ABTS radical. The ease, improved time prerequisites, and minimal reagent needs with the microtiter plate format, makes this design attractive. It would prove of particular interest to individuals engaged in both smaller and high-volume throughput antioxidant assays of food and health products, and other biological fluids and tissues.