EPR imaging and HPLC characterization of the pigment-based organic free radical in black soybean seeds.
We investigated the location and distribution of paramagnetic species in dry black, brown, and yellow (normal) soybean seeds using electron paramagnetic resonance (EPR), X-band (9 GHz) EPR imaging (EPRI), and HPLC. EPR primarily detected two paramagnetic species in black soybean. These two different radical species were assigned as stable organic radical and Mn2+species based on the g values and hyperfine structures. The signal from the stable radical was noted at g ≈ 2.00 and was relatively strong and stable. Subsequent noninvasive two-dimensional (2D) EPRI of the radical present in black soybean revealed that the stable radical was primarily located in the pigmented region of the soybean coat, with very few radicals observed in the soybean cotyledon (interior). Pigments extracted from black soybean were analyzed using HPLC. The major compound was found to be cyanidin-3-glucoside. Multi-EPR and HPLC results indicate that the stable radical was only found within the pigmented region of the soybean coat, and it could be cyanidin-3-glucoside or an oxidative decomposition product.
a Division of Regional Innovation, Graduate School of Health Sciences , Hirosaki University , Hirosaki , Japan.
Kouichi
K
Nakagawa
b Faculty of Agriculture and Life Science , Hirosaki University , Hirosaki , Aomori , Japan.
Hayato
H
Maeda
D000872:Anthocyanins / Q000032:analysis; D000975:Antioxidants / Q000032:analysis; D002851:Chromatography, High Pressure Liquid; D004578:Electron Spin Resonance Spectroscopy / Q000295:instrumentation*; D005609:Free Radicals / Q000032:analysis*; D005960:Glucosides / Q000032:analysis; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D010084:Oxidation-Reduction; D010860:Pigments, Biological / Q000032:analysis*; D012639:Seeds / Q000737:chemistry*; D013025:Glycine max / Q000737:chemistry*
D000872:Anthocyanins; D000975:Antioxidants; D005609:Free Radicals; D005960:Glucosides; D010860:Pigments, Biological; C462279:cyanidin-3-O-beta-glucopyranoside
EPR; EPR imaging; HPLC; anthocyanin; pigment radical; soybean