On chip superoxide dismutase assay for high-throughput screening of radioprotective activity of herbal plants

With the advent of new technologies, human exposure to ionizing radiation has increased. Therefore, appropriate pharmacological interventions and modalities are needed to protect humans against the deleterious effects of ionizing radiation. In this work, we developed a photosensitive, high-throughput chip-based assay for exploring the antioxidant [superoxide dismutase (SOD)]/radioprotective potential of herbal plants. Red light absorption property of nitroblue tetrazolium (NBT) formazan was applied to chip-based SOD activity measurements of six herbal plant extracts in a high-throughput manner. SOD enzyme in the photochemical reaction scavenged free radicals (O^·-₂) to form a stable carryover product (O₂ and H2O2). This in turn inhibited the development of NBT formazan in the reaction. Thus, the inhibition of NBT formazan production in reaction samples compared to their controls provides for measuresing the SOD activity of the respective samples. All herbal plant extracts showed higher SOD activities than amifostine. Pueraria root and scutellaria root had higher SOD activities whereas the apricot kernel displayed the lowest SOD activity among the herbal plant samples. In all test samples, gamma ray irradiation mildly reduced SOD activity. However, the reduction in SOD activity between 5 and 20 Gy irradiated samples was relatively remarkable for ponicirus fruit and citrus unshiu peel. The results indicate that the tested herbal plant extracts have the potential to be used as radioprotectors. Among the tested herbal extracts, pueraria root showed the highest antioxidant/radioprotective activity and can be considered as preferred radioprotector candidate.