Synthesis, Characterization and Antioxidant Activity of Two Novel Oxovanadium (IV) Curcuminoids

The reaction of bis[4-hydroxy-3-methoxyphenyl]-1,6-heptadiene-3,5-dione (curcumin) and two novel ligands of bis[4-tetrabenzylglucose-3-methoxyphenyl]-1,6-heptadiene-3,5-dione (bis(tetrabenzylglucose)curcumin) (BTBGC) and bis[4-tetraacetylglucose-3-methoxyphenyl]-1,6-heptadiene-3,5-dione (bis(tetraacetylglucose)curcumin) (BTAGC) with vanadium in methanol, in a 2:1 molar ratio, which yield the complexes of ML2 where M is [VO]2+, have been synthesized and characterized by FT-IR, mass spectrometry, 1H NMR spectroscopy and elemental analysis. These novel compounds were also examined for their antioxidant activity (using Trolox Equivalent Antioxidant Capacity (TEAC) antioxidant assay as a measure of their overall ability to scavenge free radicals compared to antioxidant standards such as Trolox); compounds with free hydroxyl groups were more active than those one whose locking such and also the metal complexes showed more activity than Trolox. The antioxidant capacity was decreased in BTBGC, BTAGC and their complexes compared to curcumin and its oxovanadium (IV) complex, corroborating the importance of curcumin’s free phenolic OH groups for scavenging oxidants potential. And also, the presence of the methoxy group increases the activity.