Location of Radical Species in a Black Pepper Seed Investigated by CW EPR and 9 GHz EPR-Imaging

摘要

The noninvasive 9 GHz Electron paramagnetic resonance (EPR)-imaging and continuous wave (CW) EPR were used to investigate locations of paramagnetic species in black pepper seeds without further irradiation. First, Lithium phthalocyanine (LiPC) phantom was used to examine 9 GHz EPR imager capabilities. The 9 GHz EPR-imager easily resolved LiPC samples spaced at ~ 2 mm distance. Then, commercially available black pepper seeds were measured. We observed signatures of three different radical species, which can be stable organic radical, Fe³⁺, and Mn²⁺ complexes. In addition, no EPR spectral change of the seed was observed after submerged in distillated H2O for one hour. The EPR and spectral-spatial EPR imaging results suggested that the three paramagnetic species are located mostly at the seed surface. Fewer radicals were found inside the seed. We demonstrated that CW EPR and 9 GHz EPR-imaging can be useful for determination of spatial distribution of paramagnetic species in various seeds.