title: Electron-transfer capacity of catechin derivatives and influence on the cell cycle and apoptosis in HT29 cells.
abstract: Galloylated and nongalloylated catechin conjugates with cysteine derivatives have been synthesized and evaluated for their capacity to scavenge free radicals and to influence crucial functions (cell cycle, apoptosis) in HT29 colon carcinoma cells. We show that the nonphenolic part of the molecule modified the capacity of catechins to donate hydrogen atoms and to transfer electrons to free radicals. Nongalloylated derivatives did not significantly influence either the cell cycle or apoptosis. Among the galloylated species, 4beta-[S-(O-ethyl-cysteinyl)]epicatechin 3-O-gallate, which showed a high electron-transfer capacity (5 e- per molecule), arrested the cell cycle and induced apoptosis as expected for galloylated catechins such as tea (-)-epigallocatechin 3-O-gallate. 4beta-[S-(N-Acetyl-O-methyl-cysteinyl)]epicatechin 3-O-gallate, which showed the highest hydrogen-donating capacity (10 H per molecule) while keeping the electron-transfer capacity low (2.9 e- per molecule), did not trigger any significant apoptosis. The gallate moiety did not appear to be sufficient for the pro-apoptotic effect of the catechin derivatives in HT29 cells. Instead, a high electron-transfer capacity is more likely to be behind this effect. The use of stable radicals sensitive exclusively to electron transfer may help to design molecules with either preventive scavenging action (high hydrogen donation, low electron transfer) or therapeutic pro-apoptotic activity (high electron transfer).
authors.affiliation: Institute for Chemical and Environmental Research (IIQAB-CSIC), Barcelona, Spain.
authors.forename: Carles
authors.initials: C
authors.lastname: Lozano
authors.forename: Lluís
authors.initials: L
authors.lastname: Juliá
authors.forename: Aurora
authors.initials: A
authors.lastname: Jiménez
authors.forename: Sonia
authors.initials: S
authors.lastname: Touriño
authors.forename: Josep J
authors.initials: JJ
authors.lastname: Centelles
authors.forename: Marta
authors.initials: M
authors.lastname: Cascante
authors.forename: Josep Lluís
authors.initials: JL
authors.lastname: Torres
mesh_terms: D017209:Apoptosis / Q000502:physiology*; D002392:Catechin / Q000737:chemistry / Q000502:physiology*; D002453:Cell Cycle / Q000502:physiology*; D002460:Cell Line; D045744:Cell Line, Tumor; D002470:Cell Survival; D003110:Colonic Neoplasms; D004578:Electron Spin Resonance Spectroscopy; D004579:Electron Transport; D006801:Humans; D007668:Kidney; D010084:Oxidation-Reduction
chemical_list: D002392:Catechin