title: Activity-guided fractionation of green tea extract with antiproliferative activity against human stomach cancer cells.
abstract: Epidemiological studies have suggested that the consumption of green tea provides protection against stomach cancer. Fractionation of green tea extract, guided by antiproliferative activity against human stomach cancer (MK-1) cells, has resulted in the isolation of six active flavan-3-ols, epicatechin (EC), epigallocatechin (EGC), epigallocatechin gallate (EGCg), gallocatechin (GC), epicatechin gallate (ECg), gallocatechin gallate (GCg), together with inactive glycosides of kaempferol and quercetin. Among the six active flavan-3-ols, EGCg and GCg showed the highest activity, EGC, GC, ECg followed next, and the activity of EC was lowest. These data suggest that the presence of the three adjacent hydroxyl groups (pyrogallol or galloyl group) in the molecule would be a key factor for enhancing the activity. Since reactive oxygen species play an important role in cell death induction, radical scavenging activity was evaluated using the DPPH (1,1-diphenyl-2-picrylhydrazyl) radical. The order of scavenging activity was ECg > or = EGCg > or = EGC > or = GC > or = EC. The compounds having a galloyl moiety showed more potent activity. The contribution of the pyrogallol moiety in the B-ring to the scavenging activity seemed to be less than that of the galloyl moiety.
authors.affiliation: kinjojun@fukuoka-u.ac.jp
authors.forename: Junei
authors.initials: J
authors.lastname: Kinjo
authors.forename: Tsuneatsu
authors.initials: T
authors.lastname: Nagao
authors.forename: Takashi
authors.initials: T
authors.lastname: Tanaka
authors.forename: Gen-ichiro
authors.initials: G
authors.lastname: Nonaka
authors.forename: Masafumi
authors.initials: M
authors.lastname: Okawa
authors.forename: Toshihiro
authors.initials: T
authors.lastname: Nohara
authors.forename: Hikaru
authors.initials: H
authors.lastname: Okabe
mesh_terms: D028241:Camellia sinensis / Q000737:chemistry*; D002455:Cell Division / Q000187:drug effects / Q000502:physiology; D006801:Humans; D008517:Phytotherapy / Q000379:methods; D010936:Plant Extracts / Q000737:chemistry / Q000302:isolation & purification / Q000494:pharmacology / Q000627:therapeutic use; D013274:Stomach Neoplasms / Q000188:drug therapy / Q000378:metabolism*; D013329:Structure-Activity Relationship; D013662:Tea / Q000737:chemistry*; D014407:Tumor Cells, Cultured / Q000166:cytology / Q000187:drug effects
chemical_list: D010936:Plant Extracts; D013662:Tea