Spectrofluorometric Determination of Catechins with 1,2-Diphenylethylenediamine

Nagaoka, Hiroaki; Toyoshima, Satoshi; Takeda, Ken

doi:10.2116/analsci.18.951

Cited by 9 publications

(6 citation statements)

References 19 publications

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“…The excitation and emission bandwidths were 5 nm. As the excitation and emission wavelength reported for EGCG is 331 and 455 nm, respectively (Nagaoka et al 2002), the background contributed by EGCG absorbance was recorded and corrected during calculation of fluorescence parameters. For the calculation of the binding constant, we used seven different concentrations of EGCG (Figs.…”

Section: Fluorescence Spectroscopymentioning

confidence: 99%

Interaction of epigallocatechin-3-gallate with β-lactoglobulin: molecular characterization and biological implication

Zorilla

Liang

Remondetto

et al. 2011

Dairy Science & Technol.

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Epigallocatechin-3-gallate (EGCG), an antioxidant present in green tea, could play an important role in the prevention of cancer. However, its bioavailability is low due to its instability in gastrointestinal environment. β-Lactoglobulin (β-Lg), the major protein in whey, is known for its capacity to bind bioactive molecules and could protect them from oxidation. Interaction between β-Lg and EGCG was investigated at pH 7.0 and 4.0 using fluorescence and Fourier transform infrared spectroscopy, and its impact on EGCG antioxidant activity was determined using the ferric-reducing antioxidant power method. EGCG bound to native or heat-denatured β-Lg by hydrogen bonding and possibly hydrophobic interaction at pH 7.0 and 4.0. The affinity of EGCG for heat-denatured β-Lg at pH 7.0 was greater than for native β-Lg and greater than its affinity for the protein in either state at pH 4.0. Complexing with β-Lg decreased the antioxidant activity of EGCG under all conditions investigated. However, the protein provided limited protection of EGCG against degradation over time, the heat-denatured form being slightly more effective at pH 7.0. This study provides insight into the characteristics of β-Lg binding with a flavonoid and its impact on the antioxidant activity of flavonoids in food systems. 茶多酚和β-乳球蛋白的相互作用:分子表征和生物学意义摘要表没食子儿茶素没食子酸酯(EGCG)是绿茶中类黄酮类多酚物质。它具有抗氧化活性,可预防和延缓癌症的发生。然而,由于不稳定性,EGCG的生物利用度比较低。β-乳球蛋白(β-LG)是牛奶中的主要乳清蛋白,可结合生物活性分子,并降低它们的氧化降解。本研究采用荧光光谱法和傅里叶变换红外光谱法研究β-LG和EGCG的相互作用,并通过铁离子还原/抗氧化能力(FRAP)法表征了β-LG对EGCG抗氧化活性的影响。当溶液pH在7.0和4.0时,EGCG与天然

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Section: Fluorescence Spectroscopymentioning

confidence: 99%

Interaction of epigallocatechin-3-gallate with β-lactoglobulin: molecular characterization and biological implication

Zorilla

Liang

Remondetto

et al. 2011

Dairy Science & Technol.

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“…For instance, melanins are reported to be responsible for the fluorescence in the retinal pigment epithelium, [48,49] melanins derived from opioid peptides are fluorescent, [50] and oxidation products formed from reactions between the natural phenol catechin and amines are fluorescent. [51] We examined the fluorescent properties of chitosan films electrochemically modified with catechin.…”

Section: Full Papermentioning

confidence: 99%

Biomimetic Pattern Transfer

Ghodssi

Elabd

et al. 2005

Adv Funct Materials

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Biological systems routinely use phenols to construct complex materials with diverse functions. Typically, these phenolic materials are generated using oxidative enzymes to initiate a cascade of uncatalyzed reactions. We mimic these processes to micropattern films of the aminopolysaccharide chitosan. Specifically, we microfabricate silicon wafers to have gold patterns, cast a chitosan film onto the patterned wafers, and commence pattern transfer by polarizing the underlying gold surfaces to electrochemically initiate the phenol reaction cascade. The electrochemically initiated reactions lead to modification of the chitosan film's chemistry, structure, and fluorescence. Further, electrochemically initiated modification of the chitosan film is localized to the interfacial region between the film and the anode, with resolution in the lateral direction of at least 20 μm. These results demonstrate that electrochemical pattern transfer provides a promising new method for micropatterning flexible films.

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“…We hypothesized that EGCG is fluorescent when excited at approximately λ Ex =280 nm and that its emission maxima are dependent on solvent. The EGCG fluorescence at the maximum of fluorescence excitation Ex max =331 nm/maximum of fluorescence emission Em max =455 nm or 550 nm was previously reported in a mixture of AN and aqueous solution significantly different from the cytoplasmic environment but solvent effects were not characterized [ 19 ]. In our study, however, it was found that EGCG fluoresces when excited at much shorter wavelengths.…”

Section: Introductionmentioning

confidence: 99%

The Spectral Properties of (-)-Epigallocatechin 3-O-Gallate (EGCG) Fluorescence in Different Solvents: Dependence on Solvent Polarity

et al. 2013

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(-)-Epigallocatechin 3-O-gallate (EGCG) a molecule found in green tea and known for a plethora of bioactive properties is an inhibitor of heat shock protein 90 (HSP90), a protein of interest as a target for cancer and neuroprotection. Determination of the spectral properties of EGCG fluorescence in environments similar to those of binding sites found in proteins provides an important tool to directly study protein-EGCG interactions. The goal of this study is to examine the spectral properties of EGCG fluorescence in an aqueous buffer (AB) at pH=7.0, acetonitrile (AN) (a polar aprotic solvent), dimethylsulfoxide (DMSO) (a polar aprotic solvent), and ethanol (EtOH) (a polar protic solvent). We demonstrate that EGCG is a highly fluorescent molecule when excited at approximately 275 nm with emission maxima between 350 and 400 nm depending on solvent. Another smaller excitation peak was found when EGCG is excited at approximately 235 nm with maximum emission between 340 and 400 nm. We found that the fluorescence intensity (FI) of EGCG in AB at pH=7.0 is significantly quenched, and that it is about 85 times higher in an aprotic solvent DMSO. The Stokes shifts of EGCG fluorescence were determined by solvent polarity. In addition, while the emission maxima of EGCG fluorescence in AB, DMSO, and EtOH follow the Lippert-Mataga equation, its fluorescence in AN points to non-specific solvent effects on EGCG fluorescence. We conclude that significant solvent-dependent changes in both fluorescence intensity and fluorescence emission shifts can be effectively used to distinguish EGCG in aqueous solutions from EGCG in environments of different polarity, and, thus, can be used to study specific EGCG binding to protein binding sites where the environment is often different from aqueous in terms of polarity.

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Spectrofluorometric Determination of Catechins with 1,2-Diphenylethylenediamine

Cited by 9 publications

References 19 publications

Interaction of epigallocatechin-3-gallate with β-lactoglobulin: molecular characterization and biological implication

Interaction of epigallocatechin-3-gallate with β-lactoglobulin: molecular characterization and biological implication

Biomimetic Pattern Transfer

The Spectral Properties of (-)-Epigallocatechin 3-O-Gallate (EGCG) Fluorescence in Different Solvents: Dependence on Solvent Polarity

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