Redox Interplay Between Glutathione, Ascorbic Acid, and Copper‐Tris Under Oxic and Anoxic Conditions

Abstract Herein, we address redox interplay between Cu, ascorbic acid (AscH), and glutathione (GSH) under oxic/anoxic in Tris‐H 2 SO 4 , pH of 7.5. UV–vis spectra of Cu:GSH with variable stoichiometric ratios display a prominent cluster centre (CC) transition band at 300 nm in direct addition rather than stepwise addition of GSH into Cu. Interestingly, peak intensity increases over time under oxic, but no change in anoxic suggesting formation of GS • radical or Cu I ‐disulfide with CC. Cu‐catalyzed AscH oxidation in presence of GSH by labile‐Cu II is expected faster than nonlabile‐Cu I , but oxidation is delayed. When Cu II is added into GSH/AscH solution with same concentration under anoxic, 266 nm peak intensity (AscH) is almost same, but 620 nm peak (Cu II ) is vanished indicating Cu‐reduction by GSH but not by AscH. The absorbance versus time trace studies are performed to understand the reaction dynamics in these specific ratios. The current waves of Cu II /Cu I couple are vanished after adding GSH, whereas addition of AscH, Cu II /Cu I does not alter but an additional peak is observed at +0.13 V attributed to AscH/Asc •− couple, which is lower from free AscH/Asc •− (+0.40 V). Interestingly, adding GSH into Cu/AscH solution, +0.13 V peak is shifted toward +0.40 V and simultaneously Cu II /Cu I peak vanishes, suggesting GSH stronger Cu‐chelator than AscH. When Cu II is added into GSH/AscH solution, only +0.40 V peak is obtained indicating Cu‐reduction by GSH in line with UV–vis.