Antioxidant Activity of Chlorogenic Acid Evaluated via EPR Spectroscopy and Its Visual Tracking in Mouse Kidney

Background/Objectives: Chlorogenic acid (CGA) is a natural antioxidant widely distributed in various plant foods, exhibiting great potential for the development of natural antioxidant agents and biomedical applications. Methods: In this study, the antioxidant activity of CGA was first characterized via electron paramagnetic resonance (EPR) spectroscopy by determining its scavenging capacity against 1,1-diphenyl-2-picrylhydrazyl (DPPH) radicals. Meanwhile, its hydroxyl radical (•OH) scavenging activity in aqueous solution was quantitatively evaluated based on the signal intensity changes of DMPO-OH• adducts. Furthermore, a fluorescein-labeled chlorogenic acid derivative (FL-CGA) was utilized to visualize the distribution of CGA in major mouse organs following tail vein injection, with a specific focus on the kidney, and to investigate its penetration capacity into podocytes. Results: The results demonstrated that 0.35 mM CGA exerted potent scavenging activity toward highly reactive and cytotoxic •OH radicals, achieving a scavenging rate of 95.2% in a system where •OH was generated by continuous UV irradiation of 5 mM H₂O₂ aqueous solution for 30 min. Additionally, FL-CGA was specifically accumulated in the kidney and localized to the lysosomes of podocytes, while no signal was detected in the endoplasmic reticulum or mitochondria. Conclusions: This study provides experimental evidence to further elucidate the mechanisms underlying CGA-mediated intervention in renal injury, and lays a foundation for the further development and clinical application of CGA as a natural dietary antioxidant.