Theaflavins, chemical structures

RP-HPLC has also been used for the analysis of flavan-3-ols and theaflavins during the study of the oxidation of flavan-3-ols in an immobilized enzyme system. Powdered tea leaves (20Qmg) were extracted with 3 X 5 ml of 70 per cent aqueous methanol at 70°C for lQmin. The combined supernatants were filtered and used for HPLC analysis. Flavan-3-ols were separated in a phenyl hexyl column (250 X 4.6 mm i.d. particle size 5 /im) at 30°C. Solvents A and B were 2 per cent acetic acid in ACN and 2 per cent acetic acid in water, respectively. Gradient elution was 0-lQmin, 95 per cent B 10-4Qmin, to 82 per cent B to 40-5Qmin 82 per cent B. The flow rate was 1 ml/min. Theaflavins were determined in an ODS column (100 X 4.6 mm i.d. particle size 3pm) at 30°C. The flow rate was 1.8 ml/min and solvent B was the isocratic mobile phase. The data demonstrated that flavan-3-ols disappear during the oxidation process while the amount of theaflavins with different chemical structures increases [177],... 

Figure 6.1 Chemical structures of flavanoids including catechins and theaflavins. These tiavanoids consisted of two major groups flavanones, including naringenin, taxifolin, and fustin, and flavanols including green tea polyphenols (EC, ECG, EGC, EGCG), black tea polyphenols (TF-1, TF-2a, TF-2b, TF-3), and oolong tea polyphenol (TSA).

FIGURE 15.3. Chemical structure of the four major black tea theaflavins. These Include (a) theaflavins (TF1), (b) Theaflavln-3-gallate (TF2a), (c) Theaflavln-3 -gallate (TF2b) and (d) Theaflavln-3,3 -gallate. 

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