title: Curcumin and its analogues as potent inhibitors of low density lipoprotein oxidation: H-atom abstraction from the phenolic groups and possible involvement of the 4-hydroxy-3-methoxyphenyl groups.
abstract: Curcumin (1,7-bis(4-hydroxy-3-methoxyphenyl)-1,6-heptadiene-3,5-dione, 1) is a yellow ingredient isolated from turmeric (Curcumin longa). It has been shown to exhibit a variety of biological activities including antioxidative activity. In order to find more active antioxidants with 1 as the lead compound we synthesized curcumin analogues, i.e., 1,7-bis(3,4-dihydroxyphenyl)-1,6-heptadiene-3,5-dione (2), 1-(3,4-dihydroxyphenyl)-7-(4-hydroxy-3-methoxyphenyl)-1,6-heptadiene-3,5-dione (3), 1-(4-hydroxy-3-methoxyphenyl)-7-(4-hydroxyphenyl)-1,6-heptadiene-3,5-dione (4), 1,7-bis (4-hydroxyphenyl)-1,6-heptadiene-3,5-dione (5), 1-(3,4-dimethoxyphenyl)-7-(4-hydroxy-3-methoxyphenyl)-1,6-heptadiene-3,5-dione (6), 1,7-bis(3,4-dimethoxyphenyl)-1,6- heptadiene-3,5-dione (7), 1,7-bis(4-methoxyphenyl)-1,6-heptadiene-3,5-dione (8), and 1,7-diphenyl-1,6-heptadiene-3,5-dione (9). Antioxidative effects of curcumin and its analogues against free radical initiated peroxidation of human low density lipoprotein (LDL) were studied. The peroxidation was initiated either by a water-soluble initiator 2,2'-azobis(2-amidinopropane hydrochloride) (AAPH), or by cupric ion (Cu2+). The reaction kinetics were monitored either by the uptake of oxygen and the depletion of alpha-tocopherol present in the native LDL, or by the formation of thiobarbituric acid reactive substances. Kinetic analysis of the antioxidation process demonstrates that these compounds, except 7, 8, and 9, are effective antioxidants against AAPH- and Cu2+ -initiated LDL peroxidation by H-atom abstraction from the phenolic groups. Compounds 2 and 3 which bear ortho-diphenoxyl functionality possess significantly higher antioxidant activity than curcumin and other analogues, and the 4-hydroxy-3-methoxyphenyl group also play an important role in the antioxidative activity.
authors.affiliation: National Laboratory of Applied Organic Chemistry, Lanzhou University, Lanzhou 730000, China.
authors.forename: Wei-Feng
authors.initials: WF
authors.lastname: Chen
authors.forename: Shui-Ling
authors.initials: SL
authors.lastname: Deng
authors.forename: Bo
authors.initials: B
authors.lastname: Zhou
authors.forename: Li
authors.initials: L
authors.lastname: Yang
authors.forename: Zhong-Li
authors.initials: ZL
authors.lastname: Liu
mesh_terms: D000975:Antioxidants / Q000494:pharmacology*; D003300:Copper / Q000494:pharmacology; D003474:Curcumin / Q000031:analogs & derivatives / Q000494:pharmacology*; D006801:Humans; D007700:Kinetics; D015227:Lipid Peroxidation / Q000187:drug effects; D008077:Lipoproteins, LDL / Q000037:antagonists & inhibitors / Q000737:chemistry; D010084:Oxidation-Reduction; D010100:Oxygen / Q000378:metabolism; D010636:Phenols / Q000737:chemistry*; D017392:Thiobarbituric Acid Reactive Substances / Q000378:metabolism; D024502:alpha-Tocopherol / Q000378:metabolism
chemical_list: D000975:Antioxidants; D008077:Lipoproteins, LDL; D010636:Phenols; D017392:Thiobarbituric Acid Reactive Substances; D003300:Copper; D024502:alpha-Tocopherol; D003474:Curcumin; D010100:Oxygen