Gamma radiation effects on free radicals, antioxidant activity, phenolic and flavonoid content in royal jelly

Effects of gamma irradiation upon royal jelly were evaluated by means of Electron Paramagnetic Resonance (EPR) spectroscopy, Spectrophotometric studies and Ultra High Performance Liquid Chromatography (UHPLC). Free radicals generation during irradiation, their stability and free radical scavenging activity were determined by EPR. Total phenolic (TPC) and flavonoid content (TFC) were detected by Spectrophotometric measurements and qualified and quantified the irradiation effect on the main groups of polyphenolic compounds UHPLC was used. The samples were gamma irradiated at dosages of 1, 5 and 10 kGy. The oxygen-centered free radicals were generated by gamma rays. Their signal increased upon increasing the applied dosage. EPR kinetic study of the stability of gamma-induced free radicals in royal jelly showed exponentially decay with time and identification of gamma sterilization is possible for 5 months after irradiation. The irradiation effect on free radical scavenging activity (FRSA) of royal jelly extracts was investigated by using the stable free radical 1,1-diphenyl-2-picrylhydrazyl (DPPH) and the antioxidant activity was rеpresented in Trolox Equivalents. The irradiation has a neglible effect on antiradical activity. The gamma treatment impacted the quantity of polyphenols depending on the radiation dosage. • Gamma radiation of royal jelly trapped oxygen-centered free radicals, which intensity increase with applied dose. • Gamma induced free radicals gradually decrease with time and identification of sterilization is possible for 5 months. • The irradiation has a neglible effect on antiradical activity. • The effect of irradiation on polyphenol and flavonoid content is dose-dependent.