Figure 1.
Structures of EGCG, catechin, and gallic acid.
A. EGCG. B. Catechin. C. Gallic acid.
Figure 2.
Spectra of EGCG in AB, AN, DMSO, and EtOH.
A. Representative absorbance spectra of EGCG in acetonitrile (AN), ethanol (EtOH), dimethylsulfoxide (DMSO, dashed line for clarity), and aqueous buffer (AB). Absorbance is expressed in logarithmic units. B. Emission spectra of EGCG in dimethylsulfoxide (DMSO), acetonitrile (AN), ethanol (EtOH), and aqueous buffer (AB). Excitation wavelength/Emmax are indicated. All spectra were taken with the same spectrofluorometer settings.
Figure 3.
Lippert plot (see Table 2 and DISCUSSION for explanations).
The Stokes shift (νA- νF)*10-3 (cm-1) was plotted against the orientation polarizability Δf for the different solvents from Table 1 according to the following calculation: (νA- νF)*10-3 (cm-1) = 104/Ex(nm) - 104/Emmax(nm) (Table 2). The labels for the smaller excitation peaks are indicated in the parentheses. The larger fluorescence maxima, which follow the Lippert-Mataga relation are indicated with open circles (), and are fitted with the linear regression (adjusted R2=0.95).