Electron spin resonance spectral analysis of irradiated royal jelly

The analysis of unpaired electron components in royal jelly was carried out using electron spin resonance (ESR) with the aim to develop a detection method for irradiated royal jelly. The ESR spectrum of royal jelly had natural signals derived from transition metals, including Fe3+ and Cu2+, and a signal line near g = 2.00. After irradiation, a new splitting asymmetric spectrum with overall spectrum width ca. 10 mT at g = 2.004 was observed. The intensities of the signals at g = 2.004 increased in proportion to the absorbed dose in samples under different storage conditions: fresh frozen royal jelly and dried royal jelly powder at room temperature. The signal intensity of the fresh frozen sample was stable after irradiation. One year after 10 kGy irradiation of dried powder, the signal intensity was sevenfold greater than before irradiation, although the intensity continued to steadily decrease with time. This stable radiation-induced radical component was derived from the poorly soluble constituent of royal jelly.