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Bulletin of the Korean Chemical Society (BKCS)

ISSN 0253-2964(Print)
ISSN 1229-5949(Online)
Volume 26, Number 5
BKCSDE 26(5)
May 20, 2005 

Determination of Catechin Compounds in Korean Green Tea Infusions under Various Extraction Conditions by High Performance Liquid Chromatography
Won Jo Cheong*, Moon Hee Park, Gyoung Won Kang, Joung Ho Ko, You Jin Seo
Korean green tea, Flavonoids, Extraction time and temperature, Multiple extraction, UV and fluorescence detection
Liquid chromatographic methods with UV and fluorescence detection have been used to determine the levels of (+)-catechin, (?)-epicatechin, (?)-epicatechin gallate, and (?)-epigallocatechin gallate in Korean green tea infusions. The extracts of Korean green tea leaves or powders in water at various temperatures (100 °C, 80 °C, 60 °C) and time, were washed with chloroform and re-extracted to ethyl acetate. The ethyl acetate phase was dried and re-dissolved in methanol and analyzed. Five catechin compounds were separated by gradient elution. The flavonoids were found decomposed on prolonged extraction, thus exhaustive extraction by a Soxhlet apparatus was found useless for green tea. Some unknown components were found in the extracts at 100 oC. When the green tea was filtered and re-extracted with new fresh water, still some flavonoids were extracted. However, the contents of flavonoids in the third extract were found negligible. The flavonoid extraction rate of green tea powders was higher than that of green tea leaves, but flavonoid decomposition of green tea powders was also faster than that of green tea leaves. The traditional way of drinking green tea was found appropriate in view of flavonoids intake.
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