Fast Determination of Catechins in Tea

Tea, one of the most consumed non-alcoholic drinks worldwide, contains catechins that are powerful antioxidants thought to provide many health benefits, including reduction of cholesterol and obesity, and protection against cardiovascular disease and cancer. The four major varieties of teas (white, green, oolong, and black) are derived from the same Camellia sinensis plant, but as they are prepared by different processing methods, their catechin concentrations can vary. Thus, it is important to establish a simple and reliable analytical method to determine catechin concentrations in different tea products.

The most abundant catechins in tea include catechin (C), epicatechin (EC), epigallocatechin (EGC), epicatechin gallate (ECG), gallocatechin (GC), gallocatechin gallate (GCG), and epigallocatechin gallate (EGCG). The method described here uses a high-resolution Dionex Acclaim® C18 RSLC column to separate and an absorbance of 280 nm to detect and quantify catechins in green and black teas in less than 20 min per injection.

Experimental

A Dionex UltiMate® 3000 Rapid Separation LC (RSLC) system was used; for system components and preparation of solutions, please refer to Dionex Application Note 275 (1).

Results and Discussion

Figure 1a shows the catechins present in a commercially available green tea. The most abundant catechin in this green tea is EGCG, which is about 50% of the total catechin content, at 135.4 mg/g.

Figure 1: Column: Acclaim 120, C18, 2.2 μm, analytical 2.1 × 150 mm. Eluent: A: 0.1% TFA, 5% CH3CN, B: 0.1% TFA in CH3CN; Gradient: 0.0–1.2 min: 100% A, 1.2–15.5 min: 28.5% B, hold for 1.5 min at 28.5% B; Temp: 25 °C, Flow-rate: 0.45 mL/min; Detection: UV 280 nm, Injection Volume: 1.0 μL. Separation of catechins in (a) Green tea and (b) Black tea with Peak 1: Gallic Acid, Peak 2: EGC, Peak 3: Caffeine, Peak 4: C, Peak 5: EC, Peak 6: EGCG, Peak 7: GCG, and Peak 8: ECG. Gallic acid and caffeine concentrations were not calculated in either of the teas. Concentration of EGC, C, EC, EGCG, GCG, and ECG were as follows: Green tea: 45.3, 3.45, 6.14, 64.0, 6.74, and 9.81 mg/g; Black tea: 27.8, 4.35, 2.25, 12.3, 9.20, and 7.47 mg/g.

Figure 1b shows an analysis of black tea, where, unlike green tea, the EGC concentration is higher than the EGCG content and the total catechin content is 63.3 mg/g, nearly 50% less than that of the green tea. The caffeine levels are also higher in black tea as compared to green tea. Both the lower total catechin concentration and the higher caffeine concentrations are consistent with the increased processing of black tea. To evaluate method accuracy, the teas were spiked with known amounts of the seven catechins. Recoveries ranged from 90.2% to 102.3%, suggesting method accuracy. An accurate analysis of these complex samples requires less than 20 min per injection.

UltiMate and Acclaim are registered trademarks of Dionex Corporation.

References

(1) Dionex Corporation. Determination of Catechins in Tea; Application Note 275, LPN 2799: Sunnyvale, CA.

Dionex Corporation

1228 Titan Way, P.O. Box 3603, Sunnyvale, CA 94088

tel. (408) 737-0700, fax (408) 730-9403

Website: www.dionex.com