Antioxidant-Based Lead Discovery for Cancer Chemoprevention: The Case of Resveratrol (Retracted Article. See vol 52, pg 6504, 2009)
State Key Laboratory of Applied Organic Chemistry, Lanzhou University, Lanzhou, Gansu, China.Journal of Medicinal Chemistry (Impact Factor: 5.45). 05/2009; 52(7):1963-74. DOI: 10.1021/jm8015415
Resveratrol is a well-known natural antioxidant and cancer chemopreventive agent that has attracted much interest in the past decade. Resveratrol-directed compounds were synthesized, and their antioxidant effects against reactive oxygen species (ROS)-induced DNA damage, their prooxidant effects on DNA damage in the presence cupric ions, and their cytotoxic and apoptosis-inducing effects on human promyelocytic leukemia (HL-60) cells were investigated in vitro. It was found that the compounds bearing o-diphenoxyl groups exhibited remarkably higher activities in inhibiting ROS-induced DNA damage, accelerating DNA damage in the presence cupric ions, and inducing apoptosis of HL-60 cells compared with the ones bearing no such groups. The detail mechanism of the structure-activity relationship was also studied by the oxidative product analysis of resveratrol and its analogues with galvinoxyl radical or cupric ions and UV-visible spectra change in the presence cupric ions. This study reveals a good and interesting correlation between antioxidant and prooxidant activity, as well as cytotoxicity and apoptosis-inducing activity against HL-60 cells, and provides an idea for designing antioxidant-based cancer chemoprevention agents.
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ABSTRACT: Resveratrol (3,5,4'-trihydroxy-trans-stilbene, 3,5,4'-THS) is a well-known natural antioxidant and cancer chemopreventive agent that has attracted much interest in the past decade. To find a more active antioxidant and investigate the antioxidative mechanism with resveratrol as the lead compound, we synthesized 3,5-dihydroxy-trans-stilbene (3,5-DHS), 4-hydroxy-trans-stilbene (4-HS) 3,4-dihydroxy-trans-stilbene (3,4-DHS), 4,4'-dihydroxy-trans-stilbene (4,4'-DHS), 4-hydroxy-3-methoxy-trans-stilbene (3-MeO-4-HS), 4-hydroxy-4'-methoxy-trans-stilbene (4'-MeO-4-HS), 4-hydroxy-4'-methyl-trans-stilbene (4'-Me-4-HS), 4-hydroxy-4'-nitro-trans-stilbene (4'-NO(2)-4-HS), and 4-hydroxy-4'-trifluoromethyl-trans-stilbene (4'-CF(3)-4-HS). The radical-scavenging activity and detailed mechanism of resveratrol and its analogues (ArOHs) were investigated by the reaction kinetics with galvinoxyl (GO(*)) and 2,2-diphenyl-1-picrylhydrazyl (DPPH(*)) radicals in ethanol and ethyl acetate at 25 degrees C, using UV-vis spectroscopy. It was found that the reaction rates increase with increasing the electron-rich environment in the molecules, and the compound bearing o-dihydroxyl groups (3,4-DHS) is the most reactive one among the examined resveratrol analogues. The effect of added acetic acid on the measured rate constant for GO(*)-scavenging reaction reveals that in ethanol that supports ionization solvent besides hydrogen atom transfer (HAT), the kinetics of the process is partially governed by sequential proton loss electron transfer (SPLET). In contrast to GO(*), DPPH(*) has a relatively high reduction potential and therefore enhances the proportion of SPLET in ethanol. The relatively low rate constants for the reactions of ArOHs with GO(*) or DPPH(*) in ethyl acetate compared with the rate constants in ethanol prove that in ethyl acetate these reactions occur primarily by the HAT mechanism. The contribution of SPLET and HAT mechanism depends on the ability of the solvent to ionize ArOH and the reduction potential of the free radical involved. Furthermore, the fate of the ArOH-derived radicals, i.e., the phenoxyl radicals, was investigated by the oxidative product analysis of ArOHs and GO(*) in ethanol. The major products were dihydrofuran dimers in the case of resveratrol, 4,4'-DHS, and 4-HS and a dioxane-like dimer in the case of 3,4-DHS. It is suggested from the oxidative products of these ArOHs that the hydroxyl group at the 4-position is much easier to subject to oxidation than other hydroxyl groups, and the dioxane-like dimer is formed via an o-quinone intermediate.The Journal of Organic Chemistry 06/2009; 74(14):5025-31. DOI:10.1021/jo9007095 · 4.72 Impact Factor
- Journal of Medicinal Chemistry 10/2009; 52(20):6504. DOI:10.1021/jm901413p · 5.45 Impact Factor
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ABSTRACT: The effectiveness of hydroxycinnamic acids (HCAs), that is, caffeic acid (CaA), chlorogenic acid (ChA), sinapic acid (SA), ferulic acid (FA), 3-hydroxycinnamic acid (3-HCA), and 4-hydroxycinnamic acid (4-HCA), as pBR322 plasmid DNA-cleaving agents in the presence of Cu(II) ions was investigated. Compounds bearing o-hydroxy or 3,5-dimethoxy groups on phenolic rings (CaA, SA, and ChA) were remarkably more effective at causing DNA damage than the compounds bearing no such groups; furthermore, CaA was the most active among the HCAs examined. The involvement of reactive oxygen species (ROS) and Cu(I) ions in the DNA damage was affirmed by the inhibition of the DNA breakage by using specific scavengers of ROS and a Cu(I) chelator. The interaction between CaA and Cu(II) ions and the influence of ethylenediaminetetraacetic acid (EDTA), the solvent, and pH value on the interaction were also studied to help elucidate the detailed prooxidant mechanism by using UV/Vis spectroscopic analysis. On the basis of these observations, it is proposed that it is the CaA phenolate anion, instead of the parent molecule, that chelates with the Cu(II) ion as a bidentate ligand, hence facilitating the intramolecular electron transfer to form the corresponding CaA semiquinone radical intermediate. The latter undergoes a second electron transfer with oxygen to form the corresponding o-quinone and a superoxide, which play a pivotal role in the DNA damage. The intermediacy of the semiquinone radical was supported by isolation of its dimer from the Cu(II)-mediated oxidation products. Intriguingly, CaA was also the most cytotoxic compound among the HCAs toward human promyelocytic leukemia (HL-60) cell proliferation. Addition of exogenous Cu(II) ions resulted in an effect dichotomy on cell viability depending on the concentration of CaA; that is, low concentrations of CaA enhanced the cell viability and, conversely, high concentrations of CaA almost completely inhibited the cell proliferation. On the other hand, when superoxide dismutase was added before, the two stimulation effects of exogenous Cu(II) ions were significantly ameliorated, thus clearly indicating that the oxidative-stress level regulates cell proliferation and death. These findings provide direct evidence for the antioxidant/prooxidant mechanism of cancer chemoprevention.Chemistry - A European Journal 11/2009; 15(46):12889-12899. DOI:10.1002/chem.200901627 · 5.73 Impact Factor
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