• Rapid Communication in Photoscience
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• 제4권3호
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• pp.59-62
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• 2015

We investigated photo-induced electron transfer (PET) in a dye-labeled peptide, fluorophore-Ala-Gly-Gln-Tyr, employing time-resolved fluorescence. As an effort to develop new functional dyes, we studied an acriflavine derivative for the electron-acceptor in the excited state from tyrosine, an electrondonor in the ground-state. The pH dependence of the fluorescence lifetime of the model peptide indicates that electron transfer between the excited dye and tyrosine occurs when the tyrosine is deprotonated. The proton-coupled electron transfer appears to be sequential rather than concerted. We also report direct time measurements on the end-to-end loop formation processes of the peptide in water.

• Bulletin of the Korean Chemical Society
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• 제35권6호
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• pp.1633-1638
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• 2014

[6]-Gingerol is known as the major bioactive constituent of ginger. In the study, it was observed to effectively protect against ${\bullet}OH$-induced DNA damage ($IC_{50}$ $328.60{\pm}24.41{\mu}M$). Antioxidant assays indicated that [6]-gingerol could efficiently scavenge various free radicals, including ${\bullet}OH$ radical ($IC_{50}$ $70.39{\pm}1.23{\mu}M$), ${\bullet}O_2{^-}$ radical ($IC_{50}$ $228.40{\pm}9.20{\mu}M$), $DPPH{\bullet}$radical ($IC_{50}$ $27.35{\pm}1.44{\mu}M$), and $ABTS{^+}{\bullet}$radical ($IC_{50}$ $2.53{\pm}0.070{\mu}M$), and reduce $Cu^{2+}$ ion ($IC_{50}$ $11.97{\pm}0.68{\mu}M$). In order to investigate the possible mechanism, the reaction product of [6]-gingerol and $DPPH{\bullet}$ radical was further measured using HPLC combined mass spectrometry. The product showed a molecular ion peak at m/z 316 $[M+Na]^+$, and diagnostic fragment loss (m/z 28) for quinone. On this basis, it can be concluded that: (i) [6]-gingerol can effectively protect against ${\bullet}OH$-induced DNA damage; (ii) a possible mechanism for [6]-gingerol to protect against oxidative damage is ${\bullet}OH$ radical scavenging; (iii) [6]-gingerol scavenges ${\bullet}OH$ radical through hydrogen atom ($H{\bullet}$) transfer (HAT) and sequential electron (e) proton transfer (SEPT) mechanisms; and (iv) both mechanisms make [6]-gingerol be oxidized to semi-quinone or quinone forms.

• Bulletin of the Korean Chemical Society
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• 제35권1호
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• pp.117-122
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• 2014

As a Chinese herbal medicine used in East Asia for thousands years, Cortex Magnoliae Officinalis (CMO) was observed to possess a protective effect against OH-induced DNA damage in the study. To explore the mechanism, the antioxidant effects and chemical contents of five CMO extracts were determined by various methods. On the basis of mechanistic analysis, and correlation analysis between antioxidant effects & chemical contents, it can be concluded that CMO exhibits a protective effect against OH-induced DNA damage, and the effect can be attributed to the existence of phenolic compounds, especially magnolol and honokiol. They exert the protective effect via antioxidant mechanism which may be mediated via hydrogen atom transfer (HAT) and/or sequential electron proton transfer (SEPT). In the process, the phenolic-OH moiety in phenylpropanoids is oxidized to the stable quinine-like form and the stability of quinine-like can be ultimately responsible for the antioxidant.