Catechins, the main ingredients of tea, have a wide variety of effects and benefits, and their functions have been attracting attention.Green tea and oolong tea are known as functional foods, and products with increased catechins are marketed as foods for specified health uses.
Unlike tea traditionally brewed with a teapot, commercial PET bottled green tea drinks include thermal isomers*1formed during the pasteurization process in non-negligible concentrations, in addition to catechins derived from tea leaves. The physiological effects of these thermal isomers have been attracting attention. There is a wide variety of catechin effects and benefits, including cancer and mutation prevention, anti-tumor, antioxidant, and antibacterial effects, as well as lowering of blood cholesterol and elimination of active oxygen. Due to those effects and benefits, research on tea catechins has been actively conducted.
Sample
Catechin standard samples
Conditions
| Column | HITACHI LaChrom C18(5 µm) (4.6 mmI.D. x 150 mm) |
|---|---|
| Mobile phase | (A) 0.05% H3PO4(pH2.4) (B) CH3OH/CH3CN = 3/2 *Gradient: (0 min) B10% → (15 min) B25% → (25 min) B60% → (25.1 – 40 min) B10% |
| Flow rate | 1.0 mL/min |
| Column Temperature | 40°C |
| Detection | UV 280 nm |
| Injection vol. | 10 µL |
Analysis results of standard samples
Linearity
Linear standard curves have been obtained in the concentration range of 1 – 50 mg/L ((-)-epigallocatechin: 5 -50 mg/L, caffeine: 1 – 200 mg/L).
Sample analysis example
Commercial PET bottled green tea
Sample pretreatment method: analysis after filtration through 0.45 µm filters
The following were detected in Samples A and B: 4 types of catechins, including (-)-epigallocatechin gallate (EGCG), (-)-epigallocatechin (EGC),(-)-epicatechin gallate (ECG), and (-)-epicatechin (EC), as well as thermal isomers, including (-)-gallocatechin (GC), (-)-Gallocatechin gallate (GCG), and (-)-Catechin gallate (CG).
Note that the simultaneous analysis of the caffeine contained in tea can be performed under these analysis conditions.
