CHARACTERIZATION STUDIES ON A TETRAHYDROCURCUMIN-ZINC COMPLEX

Abstract

Objective: Preparation and characterization studies on tetrahydrocurcumin complexed with zinc, with particular reference to the location of zinc in the complex. Methods: Structural characteristics of tetrahydrocurcumin and its complex with zinc were compared using elemental analysis, mass spectrometry (MS), proton, and carbon-13 nuclear magnetic resonance spectroscopy (NMR), ultraviolet-visible (UV) absorption spectroscopy, and Fourier transform infrared (FTIR) spectroscopy. Results: MS data indicates a Zn molecule holds two THCur components together. NMR data provide evidence that the zinc ion is associated with the 1,3-diketone part of the linker region of the associated THCur. FTIR data is consistent with zinc interaction with the enol tautomer of the 1,3-diketone at the center of the linker region of THCur. UV data indicate that a zinc-dependent shift in absorbance maximum is consistent with changes in the structure of THCur resulting from complexation with zinc. Together, this data indicates the complexation of zinc with tetrahydrocurcumin is consistent with zinc linking two molecules of tetrahydrocurcumin together by binding to the enol forms of the 1,3-diketone moieties located in the linker regions between the aromatic rings. Conclusion: The spectral properties of the tetrahydrocurcumin-zinc complex are consistent with a structure in which zinc is encased in two tetrahydrocurcumin moieties. Additional studies are needed to determine if this structure results in altered bioavailability, antioxidant activity and other properties important for pharmaceutical development.