title: Quantitative analysis of major constituents in green tea with different plucking periods and their antioxidant activity.
abstract: The objective of this study was to determine the relationship between the plucking periods and the major constituents and the antioxidant activity in green tea. Green tea was prepared from leaves plucked from the end of April 2013 to the end of May 2013 at intervals of one week or longer. The contents of theanine, theobromine, caffeine, catechin (C), and gallocatechin gallate (GCg) were significantly decreased, whereas those of epicatechin (EC), epigallocatechin gallate (EGCg) and epigallocatechin (EGC) were significantly increased along with the period of tea leaf plucking. In addition, antioxidant activity of green tea and standard catechins was investigated using ABTS, FRAP and DPPH assays. The highest antioxidant activity was observed in relatively the oldest leaf, regardless of the assay methods used. Additionally, the order of antioxidant activity of standard catechins was as follows: EGCg≥GCg≥ECg>EGC≥GC≥EC≥C. Moreover, the cis-catechins contents were the key factor affecting the antioxidant activity of green tea in all assays employed (ABTS, r=0.731, p<0.01; FRAP, r=0.886, p<0.01; DPPH, r=0.778, p<0.01).
authors.affiliation: Korea Food Research Institute, Seongnam, Kyonggi 463-746, Korea. sohee0809@hanmail.net.
authors.forename: Lan-Sook
authors.initials: LS
authors.lastname: Lee
authors.affiliation: Korea Food Research Institute, Seongnam, Kyonggi 463-746, Korea. kimsh@kfri.re.kr.
authors.forename: Sang-Hee
authors.initials: SH
authors.lastname: Kim
authors.affiliation: Korea Food Research Institute, Seongnam, Kyonggi 463-746, Korea. kybaaa@kfri.re.kr.
authors.forename: Young-Boong
authors.initials: YB
authors.lastname: Kim
authors.affiliation: Korea Food Research Institute, Seongnam, Kyonggi 463-746, Korea. yckim@kfri.re.kr.
authors.forename: Young-Chan
authors.initials: YC
authors.lastname: Kim
mesh_terms: D052160:Benzothiazoles / Q000737:chemistry; D001713:Biphenyl Compounds / Q000737:chemistry; D002110:Caffeine / Q000737:chemistry / Q000302:isolation & purification; D028241:Camellia sinensis / Q000737:chemistry*; D002392:Catechin / Q000031:analogs & derivatives / Q000737:chemistry / Q000302:isolation & purification; D016166:Free Radical Scavengers / Q000737:chemistry / Q000302:isolation & purification*; D005609:Free Radicals / Q000737:chemistry; D005971:Glutamates / Q000737:chemistry / Q000302:isolation & purification; D010851:Picrates / Q000737:chemistry; D010936:Plant Extracts / Q000737:chemistry / Q000302:isolation & purification*; D018515:Plant Leaves / Q000737:chemistry*; D013451:Sulfonic Acids / Q000737:chemistry
chemical_list: D052160:Benzothiazoles; D001713:Biphenyl Compounds; D016166:Free Radical Scavengers; D005609:Free Radicals; D005971:Glutamates; D010851:Picrates; D010936:Plant Extracts; D013451:Sulfonic Acids; C002502:2,2'-azino-di-(3-ethylbenzothiazoline)-6-sulfonic acid; D002110:Caffeine; C026166:theanine; D002392:Catechin; C062669:epicatechin gallate; C004931:1,1-diphenyl-2-picrylhydrazyl