Catechins are in a polyphenol group contained in green tea that yield a bitter taste. They have various physiological functions and have been reported to inhibit high blood pressure, control blood cholesterol, control blood-sugar level, and provide antioxidative, anti-aging, anti-bacterial and anti-allergic activities. The main constituents of catechins in green tea are epicatechin, epigallocatechin, epicatechin gallate, and epigallocatechin gallate.
In this article, catechins in green tea were measured and analyzed by Ultra High-performance Liquid Chromatography(UHPLC) with Photodiode Array Detection.
LC-4000 UHPLC system
Column: ZORBAX SB-C18 (3.0 mmID x 50 mmL, 1.8 µm)
Eluent A: 0.2% Phosphoric acid in Water/Acetonitrile (90/10)
Eluent B: 0.2% Phosphoric acid in Water/Acetonitrile (50/50)
Gradient condition (A/B): 0 min(100/0) -> 4 min(70/30) -> 4.5 min(70/30) -> 4.55 min(0/100) -> 5 min(0/100) -> 5.05 min(100/0), 1 cycle; 7.5 min
Flow rate: 0.8 mL/min
Column temp.: 30ºC
Wavelength: 200-400 nm
Injection volume: 1 mL
Standard sample: 6 catechins and caffeine
Figure 1 shows chemical structures of 6 catechins and caffeine.
Figure 1. Chemical structures 6 catechins and caffeine
UHPLC, Green tea, Catechine,1.8 mm, C18 Column, PDA detector
Figure 2 shows a chromatogram and a contour plot of 6 catechines and caffeine. It shows that the 7 different constituents are completely separated within 4 minutes.
Figure 2. Chromatogram and contour plot of 6 catechines and caffeine (1: EGC (500 µg/mL), 2: C (100 µg/mL), 3: Caffeine (10 µg/mL), 4: EC (100 µg/mL), 5: EGCG (25 µg/mL), 6: ECG (20 µg/mL), 7: CG (100 µg/mL))
Figure 3 shows a chromatogram and a contour plot of green tea. It shows that the 7 different constituents and impurities were separated properly.
Figure 3. Chromatogram and contour plot of green tea extract (The peak numbers and corresponding compounds are the same as in figure 2.)
Sample preparation: The sample was filtered using 0.2 mm membrane filter.