ORAC assay to determine antioxidant capacity

Franka Ganske BMG LABTECH 12/2014

Oxygen consuming cells generate intermediates and byproducts known as reactive oxygen species (ROS). As they harm biomolecules, ROS are involved in aging and in the development of degenerative diseases. Biological antioxidants are able to dispose ROS. However, they are not completely effective in eliminating all ROS.


A standardized method for determining the antioxidant capacity of a substance is the ORAC (oxygen radical absorbance capacity) assay. Recent modifications to this assay include the use of fluorescein as the probe, the adaptation to a high-throughput format, and the ability to measure the lipophilic, hydrophilic, and total antioxidant capacity of a substance. Herein we describe the application of the ORAC-FL assay using Trolox® as a standard by which all other antioxidant compounds are compared.


Using a BMG LABTECH microplate reader, the assay was followed in real-time and the use of onboard injectors allowed for consistent and reproducible data.

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