Cody E. Mingle, Anthony L. Newsome, Identification of Antioxidant Activity of Medicinal Plant Extracts Through a Modified and Rapid ABTS Colorimetric Assay, Journal of Antioxidant Activity, Volume 2, Issue 4, 2026, Pages 40-46, ISSN 2471-2140, https://doi.org/10.14302/issn.2471-2140.jaa-26-6462.
(https://oap-researchnetwork.org/antioxidant-activity/article/identification-of-antioxidant-activity-of-medicinal-plant-extracts-through-a-modified-and-rapid-abts-colorimetric-assay-2407)
Abstract: The consumption of antioxidant rich plants is a common human activity. Therefore, easily used, time efficient and effective antioxidant assays of plants consumed by humans are of increasing importance. The ABTS [2,2’-azinobis-(3-ethtlbenzothiazoline-6-sulfonic acid)] cation radical is commonly used in colorimetric assays to assess antioxidant properties of test compounds. Oxidation of ABTS (7.0 mM) to the ABTS radical is often performed by overnight (6-12 h) reaction with 2.45 mM potassium persulfate. This was subsequently followed by dilution of the radical to an appropriate working absorbance at 734 nm. Described in the current study is the incorporation of 0.7 mM ATBS (rather than the previously described 7.0 mM) that rapidly (30 min) goes to complete oxidation and formation of the ABTS cation radical. This rapidly provided a suitable stable radical for antioxidant studies, thus circumventing the need for overnight (6-12 h) incubation. This protocol was subsequently incorporated into a microtiter (high-throughput) plate format. Thus, multiple dilutions and determinations of antioxidant activity of test compounds could be determined in less than one hour, which included time for formation of the ABTS radical. This protocol was successfully used to determine antioxidant activity in plant extracts that are widely used dietary supplements and consumed most often in the form of tea. Results showed that antioxidant activity of certain plant extracts at higher concentrations (125 µg/ml) was comparable to a Trolox standard. Plant extract antioxidant activity rapidly diminished in a stepwise manner following twofold serial dilutions in the microtiter plate format. Trolox antioxidant activity diminished in a stepwise fashion at much higher dilutions. The spectrophotometric absorbance readings were highly reproducible with a characteristically low standard deviation. Application of this rapid colorimetric assay in the identification of antioxidant properties has notable results in these traditionally used plants along with potential for use in future studies of plant constituents.
Keywords: ABTS assay; rapid high throughput; plant extracts; Cyclocarya paliurus; Gynostemma pentaphyllum; Usnea diffract