Antioxidant novel activities of curcumin complexes with Mg(II), Ca(II), Cu(II), Cr(III) and Se(IV) metal ions: synthesis and spectral studies

Curcumin (Cur) metal complexes of Mg(II), Ca(II), Cu(II), Cr(III), and Se(IV) were prepared and characterized using elemental analysis, molar conductance, IR, UV-spectra, 1H NMR, SEM, TEM, and X-ray diffraction. The very low values of molar conductance confirm that Cl- ions are absent inside or outside the chelation sphere confirming their non-electrolytic nature, while for Cr(III) Cur is high compared to other curcumin complexes, confirming that Cl- ions are inside the complexation sphere. Based on IR and electronic spectra, the Cur C=O group in enol form chelated to Mg(II), Ca(II), Cu(II), Cr(III), and tetravalent metal (Se). The surface morphology of the curcumin chelates showed an increase in particle size and irregular grains shaped with an elongated morphology. Transmission electron microscopy revealed that the Cur chelates have spherical black spots like shape with a particle size of 72.21-88.75 nm, 34.89-57.33 nm, and 80.71-100 nm for Cu(II), Zn(II), and Se(IV) Cur respectively. X–ray powder diffraction patterns for Cu(II) Cur complexes showed particle size within 70-90 nm; the antioxidant activities of Cur and its metal complexes were assessed. Results showed that the Cur complexes with Cr, Mg, Ca, Cu, or Se showed potent antioxidant activities. Further studies could evaluate the potency of these complexes to elevate the antioxidant defense system and enhance body functions against degenerative diseases, such as aging, Alzheimer's disease, and viral diseases. KEY WORDS: Curcumin, Mg/Cur, Cu/Cur, Se/Cur, Electronic spectra, Antioxidant, Oxidative stress Bull. Chem. Soc. Ethiop. 2024, 38(2), 347-363. DOI: https://dx.doi.org/10.4314/bcse.v38i2.6