Role of phenolic O-H and methylene hydrogen on the free radical reactions and antioxidant activity of curcumin

Electron Paramagnetic Resonance Study of the Free Radical Scavenging Capacity of Curcumin and Its Demethoxy and Hydrogenated Derivatives

“…This may be related primarily to the differences in the ability to donate hydrogen atoms from a phenolic vs. enolic group due the differences in their chemical structure. [7][8][9]15,16,24,25) The additional hydroxyl group in OHC and the hydrogen atom from the central methylenic group may also contribute to the hydrogen donating ability of these hydrogenated derivatives. 26) In addition, the results confirmed that loss of the orthomethoxyphenolic group in Bdmc caused a greater loss of hydrogen donating activity, whereas the molecule with an ortho-methoxyphenolic group and β-diketone moiety showed the comparable activity to trolox.…”

“…3,4) As a potent anti-oxidant, several mechanisms have been proposed which describe the direct interaction of curcumin with reactive oxygen species (ROS) as well as its involvement in ROS-independent mechanisms (i.e., induction of antioxidant enzymes). 5,6) The structure-antioxidant activity relationship of curcumin and the compound it reduces has been demonstrated in both in vitro and in vivo models, for example, 1,1-diphenyl-2-picrylhydrazyl (DPPH) kinetic analysis, γ-radiolysis of rat liver microsomes, 7) 2,2′-azobis(2-amidinopropane)dihydrochloride (AAPH)-induced low density lipoprotein (LDL) oxidation, 8) AAPH-induced linoleic oxidation. 9) Lastly, the protective effects of curcumin on oxidative injury have been demonstrated in vivo in several animal diseases models.…”

Effect of Curcumin Against Oxidation of Biomolecules by Hydroxyl Radicals

“…Its unique conjugated structure includes two phenols and an enol form of a β-diketone. Antioxidant mechanisms of curcumin have been studied by laser flash photolysis and pulse radiolysis, and it was found that the keto-enol-enolate equilibrium of the heptadienone moiety of curcumin determined its physicochemical and antioxidant properties [57,58]. Hence overall antioxidant effect of curcumin on the oxidative stress induced by aerobic metabolism has proved to be effective.…”

Direct chemical grafted curcumin on halloysite nanotubes as dual-responsive prodrug for pharmacological applications

“…In particular, the antioxidant properties are attributed to the phenolic OH groups and the CH 2 group of the ␤-diketone moiety, which is in equilibrium with its enol tautomer [57][58][59]. Curcumin has been shown to inhibit lipid peroxidation and to manifest free radical-scavenging activity, in particular toward oxygen and nitrogen-centered free radicals.…”