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

• Published in: Biological & pharmaceutical bulletin Vol. 38; no. 10; pp. 1478 - 1483
• Main Authors: Morales, Noppawan Phumala, Sirijaroonwong, Srisuporn, Yamanont, Paveena, Phisalaphong, Chada
• Format: Journal Article
• Language: English; Japanese
• Published: Japan The Pharmaceutical Society of Japan 01.10.2015; Pharmaceutical Society of Japan; Japan Science and Technology Agency
• Subjects: Biphenyl Compounds - chemistry; curcumin; Curcumin - analogs & derivatives; Curcumin - chemistry; electron paramagnetic resonance; Electron Spin Resonance Spectroscopy; free radical scavenger; Free Radical Scavengers - chemistry; Hydroxyl Radical - chemistry; Nitric Oxide - chemistry; Picrates - chemistry; spin trapping; Superoxides - chemistry
• ISSN: 0918-6158; 1347-5215
• DOI: 10.1248/bpb.b15-00209

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.