AUTHOR=Irto Anna , Cigala Rosalia Maria , Alessandrello Chiara , De Stefano Concetta , Gattuso Giuseppe , Crea Francesco TITLE=Binary and ternary complexes of epinephrine with alginate and biologically and environmentally relevant metal cations JOURNAL=Frontiers in Chemistry VOLUME=11 YEAR=2023 URL=https://www.frontiersin.org/journals/chemistry/articles/10.3389/fchem.2023.1189308 DOI=10.3389/fchem.2023.1189308 ISSN=2296-2646 ABSTRACT=

The speciation of epinephrine (Eph⁻) in the presence of alginate (Alg^2-) and two biological and environmental relevant metal cations (Cu²⁺, UO₂²⁺) was investigated at T = 298.15K, I = 0.15–1.00 mol dm⁻³ in NaCl_(aq). The formation of binary and ternary complexes was evaluated and, since epinephrine can behave as a zwitterion, the Eph⁻/Alg^2- interaction was studied by means of DOSY NMR. The dependence of the equilibrium constants on ionic strength was studied using an extended Debye-Hückel type equation and the SIT approach. The effect of temperature was investigated by means of isoperibolic titration calorimetry: the entropic contribution was the driving force for the Cu²⁺/Eph⁻ complexes formation. The sequestering ability of Eph⁻ and Alg^2- on Cu²⁺, evaluated by the pL_0.5 calculation, increased with pH and ionic strength. The determination of pM parameter showed that Eph⁻ had a higher Cu²⁺ affinity with respect to Alg^2-. The formation of Eph⁻/Alg^2- species was also investigated by UV-Vis spectrophotometry and ¹H NMR measurements. The ternary Cu²⁺/Eph⁻/Alg^2- and Cu²⁺/UO₂²⁺/Eph⁻ interactions were also studied. The “extra-stability” calculated for the mixed ternary species confirmed that their formation was thermodynamically favorable.