title: Electron Paramagnetic Resonance Study of the Free Radical Scavenging Capacity of Curcumin and Its Demethoxy and Hydrogenated Derivatives.
abstract: The quantitative free radical scavenging capacity of curcumin and its demethoxy derivatives (demethoxycurcumin (Dmc) and bisdemethoxycurcumin (Bdmc)) and hydrogenated derivatives (tetrahydrocurcumin (THC), hexahydrocurcumin (HHC) and octahydrocurcumin (OHC)) towards 1,1-diphenyl-2-picryl hydrazyl (DPPH), nitric oxide radical (NO), hydroxyl radical (HO(·)) and superoxide anion radical (O2(·)) were investigated by electron paramagnetic resonance (EPR) spectroscopy. One mole of the hydrogenated derivatives scavenged about 4 mol of the DPPH radical, while curcumin and Dmc scavenged about 3 mol of the DPPH radical. Curcumin and THC showed moderate scavenging activity towards NO, yielding 200 mmol of NO scavenged per 1 mol of the scavenger. In contrast, curcumin and its derivatives showed very low scavenging activity towards HO(·) and O2(·), yielding approximately only 3-12 mmol scavenged per 1 mol of the tested compounds. Our results suggest that curcumin and its derivatives principally act as chain breaking antioxidants rather than as direct free radical scavengers. Furthermore, we showed that the ortho-methoxyphenolic group and the heptadione linkage of these molecules greatly contributed to their DPPH and NO scavenging activity.
authors.affiliation: Department of Pharmacology, Faculty of Science, Mahidol University.
authors.forename: Noppawan Phumala
authors.initials: NP
authors.lastname: Morales
authors.forename: Srisuporn
authors.initials: S
authors.lastname: Sirijaroonwong
authors.forename: Paveena
authors.initials: P
authors.lastname: Yamanont
authors.forename: Chada
authors.initials: C
authors.lastname: Phisalaphong
mesh_terms: D001713:Biphenyl Compounds / Q000737:chemistry; D003474:Curcumin / Q000031:analogs & derivatives* / Q000737:chemistry*; D004578:Electron Spin Resonance Spectroscopy; D016166:Free Radical Scavengers / Q000737:chemistry*; D017665:Hydroxyl Radical / Q000737:chemistry; D009569:Nitric Oxide / Q000737:chemistry; D010851:Picrates / Q000737:chemistry; D013481:Superoxides / Q000737:chemistry
chemical_list: D001713:Biphenyl Compounds; D016166:Free Radical Scavengers; D010851:Picrates; D013481:Superoxides; D009569:Nitric Oxide; D017665:Hydroxyl Radical; C004931:1,1-diphenyl-2-picrylhydrazyl; D003474:Curcumin