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KMID : 0380620090410010082
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Korean Journal of Food Science and Technology
2009 Volume.41 No. 1 p.82 ~ p.86
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Comparative Analysis of Catechins and Antioxidant Capacity in Various Grades of Organic Green Teas Grown in Boseong, Korea
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Park Kyung-Ryun
Lee Sang-GIl
Nam Tae-Gyu
Kim Young-Jun
Kim Young-Rok
Kim Dae-Ok
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Abstract
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The objective of this study was to evaluate the effect of various solvents on extraction of bioactive phenolicsand to analyze the antioxidant capacity and contents of individual catechins in various grades of green teas organicallygrown in Boseong, Korea. The organic green teas, based on their harvest seasons, were categorized into five grades suchas Woo-Jeon, Se-Jak, Jung-Jak, Dae-Jak, and coarse tea. Solvents used to extract phenolics from these teas included waterat 23oC and 70oC as well as 80% (v/v) aqueous methanol and ethanol. In general, aqueous organic solvents of methanoland ethanol led to higher extraction yields of phenolics than water at 23oC and 70oC. Total phenolics and antioxidantcapacity of the teas extracted with the aqueous organic solvents were approximately 1.5 to 3.2 and 1.8 to 3.8 times higherthan those with water at 23oC and 70oC, respectively. Coarse tea, the lowest grade of green tea, showed approximately 30-60% lower total phenolics and antioxidant capacity compared with the higher grade ones. Reversed-phase HPLC analysiswas performed quantitatively to identify individual catechins, gallic acid, and caffeine in teas extracted with 80% (v/v)aqueous methanol. Based on their dry weights, the organic green teas contained about 1.7 to 2.9% of caffeine. Content(mg/g dry weight) of tea catechins decreased in the following order: Woo-Jeon (155.4)>Se-Jak (147.7)>Jung-Jak(143.2)>coarse tea (135.1)>Dae-Jak (130.5). (-)-Epigallocatechin gallate was the most abundant among the catechinsanalyzed. The highest grade of green tea, Woo-Jeon, had the highest amount of (-)-epigallocatechin gallate at 77.4mg/g dryweight. Overall, the higher grade of organic green teas tended to have the higher level of antioxidant capacity and catechins.
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KEYWORD
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organic green teas, catechins, HPLC, total phenolics, antioxidant capacity
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