Determination of antioxidant capacity of glutathione encapsulated in alginate microcapsules using spectrophotometric and electrochemical methods

This paper includes the preparation and physicochemical characterization of sodium alginate microcapsules intended for the oral administration of glutathione (GSH), a vital endogenous antioxidant in combating oxidative stress. Using various methods such as optical microscopy, FTIR spectrometry, and cyclic voltammetry, the morphology, chemical structure, release mechanism, and antioxidant capacity of the released glutathione in simulated digestive fluids (gastric medium with pH=2 and intestinal medium with pH=7.4, without enzymes) were analyzed. The results showed the stability of the alginate microcapsules in digestive fluids and highlighted an increase in encapsulation efficiency with higher concentrations of encapsulated glutathione. Additionally, it was shown that sodium alginate-based microcapsules exhibit different swelling capacities depending on the pH and glutathione concentration, showing remarkable potential for controlled delivery of the active compound. The in vitro release study demonstrated more efficient release of glutathione in simulated intestinal fluid (SIF) than in simulated gastric fluid (SGF). The calculation of the electrochemical index using cyclic voltammetry demonstrated superior antioxidant activity of encapsulated glutathione compared to free glutathione. Correlating the DPPH inhibition percentage with the electrochemical index showed high Pearson coefficients both in SGF and in SIF, indicating a good correlation between DPPH or ABTS free radical species inhibition and electrochemical measurements. Therefore, sodium alginate and glutathione microcapsules show potential for developing efficient delivery systems for glutathione or other pharmaceutical compounds.