Comparative Analysis of Catechins and Antioxidant Capacity in Various Grades of Organic Green Teas Grown in Boseong, Korea

보성산 유기농 녹차의 품질에 따른 카테킨 함량과 항산화능 비교 분석

  • Park, Kyung-Ryun (Department of Food Science and Technology and Institute of Life Science and Resources, Kyung Hee University) ;
  • Lee, Sang-Gil (Department of Food Science and Technology and Institute of Life Science and Resources, Kyung Hee University) ;
  • Nam, Tae-Gyu (Department of Food Science and Technology and Institute of Life Science and Resources, Kyung Hee University) ;
  • Kim, Young-Jun (Department of Food and Biotechnology, Korea University) ;
  • Kim, Young-Rok (Department of Food Science and Technology and Institute of Life Science and Resources, Kyung Hee University) ;
  • Kim, Dae-Ok (Department of Food Science and Technology and Institute of Life Science and Resources, Kyung Hee University)
  • 박경련 (경희대학교 식품공학과 및 생명자원과학연구원) ;
  • 이상길 (경희대학교 식품공학과 및 생명자원과학연구원) ;
  • 남태규 (경희대학교 식품공학과 및 생명자원과학연구원) ;
  • 김영준 (고려대학교 식품생명공학과) ;
  • 김영록 (경희대학교 식품공학과 및 생명자원과학연구원) ;
  • 김대옥 (경희대학교 식품공학과 및 생명자원과학연구원)
  • Published : 2009.02.28

Abstract

The objective of this study was to evaluate the effect of various solvents on extraction of bioactive phenolics and to analyze the antioxidant capacity and contents of individual catechins in various grades of green teas organically grown in Boseong, Korea. The organic green teas, based on their harvest seasons, were categorized into five grades such as Woo-Jeon, Se-Jak, Jung-Jak, Dae-Jak, and coarse tea. Solvents used to extract phenolics from these teas included water at $23^{\circ}C$ and $70^{\circ}C$ as well as 80% (v/v) aqueous methanol and ethanol. In general, aqueous organic solvents of methanol and ethanol led to higher extraction yields of phenolics than water at $23^{\circ}C$ and $70^{\circ}C$. Total phenolics and antioxidant capacity of the teas extracted with the aqueous organic solvents were approximately 1.5 to 3.2 and 1.8 to 3.8 times higher than those with water at $23^{\circ}C$ and $70^{\circ}C$, 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 analysis was 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 catechins analyzed. The highest grade of green tea, Woo-Jeon, had the highest amount of (-)-epigallocatechin gallate at 77.4 mg/g dry weight. Overall, the higher grade of organic green teas tended to have the higher level of antioxidant capacity and catechins.

Keywords

organic green teas;catechins;HPLC;total phenolics;antioxidant capacity

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