Binary and ternary complexes of epinephrine with alginate and biologically and environmentally relevant metal cations

Anna Irto; Rosalia Maria Cigala; Chiara Alessandrello; Concetta De Stefano; Giuseppe Gattuso; Francesco Crea

doi:10.3389/fchem.2023.1189308

Binary and ternary complexes of epinephrine with alginate and biologically and environmentally relevant metal cations

Front Chem. 2023 Apr 25:11:1189308. doi: 10.3389/fchem.2023.1189308. eCollection 2023.

Authors

Anna Irto¹, Rosalia Maria Cigala¹, Chiara Alessandrello¹, Concetta De Stefano¹, Giuseppe Gattuso¹, Francesco Crea¹

Affiliation

¹ Dipartimento di Scienze Chimiche, Biologiche, Farmaceutiche ed Ambientali, Messina, Italy.

Abstract

The speciation of epinephrine (Eph ^-) in the presence of alginate (Alg ^2-) and two biological and environmental relevant metal cations (Cu²⁺, UO₂ ²⁺) 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⁺/UO₂ ²⁺/Eph ^- interactions were also studied. The "extra-stability" calculated for the mixed ternary species confirmed that their formation was thermodynamically favorable.

Keywords: Cu2+ and UO22+ sequestration; DOSY NMR; alginate; epinephrine; extra-stability; ligand-ligand interaction; ternary complexes.

Grants and funding

The publication fee will be partially covered by the Fondo di Finanziamento per le Attività Base di Ricerca (F.F.A.B.R.) year 2020. The authors thank the University of Messina for FFABR 2020 financing.