EPR analysis of free radical components and antioxidant activity of bee pollen before and after gamma-irradiation

Gamma-induced free radicals and antiradical activity of bee pollen were evaluated by means of Electron Paramagnetic Resonance (EPR) spectroscopy. Total phenolic and flavonoid contents were spectrophotometrically determined. Two bee pollen samples of consecutive crops were exposed to gamma-irradiation. The O-centered free radicals were induced by gamma rays. Their signal increased upon increasing the dose used. The fading kinetics of free radicals was different for the two samples and they were stable for 5 months. The irradiation effect on radical scavenging activity of pollen extracts was investigated by using the stable free radical 1,1-diphenyl-2-picrylhydrazyl (DPPH) and the antioxidant activity was represented in Trolox Equivalents. It was found out that the gamma irradiation affects the antioxidant activity of pollen samples. There is a difference between the radical scavenging activities of the two samples before and after irradiation. The EPR results are in good correspondence with the determined contents of polyphenol compounds. (author)