Flavonoids, flavonoid metabolites, and phenolic acids inhibit oxidative stress in the neuronal cell line HT-22 monitored by ECIS and MTT assay: a comparative study.
A real-time and label-free in vitro assay based on electric cell-substrate impedance sensing (ECIS) was established, validated, and compared to an end-point MTT assay within an experimental trial addressing the cytoprotective effects of 19 different flavonoids, flavonoid metabolites, and phenolic acids and their methyl esters on the HT-22 neuronal cell line, after induction of oxidative stress with tert-butyl hydroperoxide. Among the flavonoids under study, only those with a catechol unit and an additional 4-keto group provided cytoprotection. The presence of a 2,3-double bond was not a structural prerequisite for a neuroprotective effect. In the case of the phenolics, catechol substitution was the only structural requirement for activity. The flavonoids and other phenolics with a ferulic acid substitution or a single hydroxy group showed no activity. Electrochemical characterization of all compounds via square-wave voltammetry provided a rather specific correlation between cytoprotective activity and redox potential for the active flavonoids, but not for the active phenolics with a low molecular weight. Moreover this study was used to compare label-free ECIS recordings with results of the established MTT assay. Whereas the former provides time-resolved and thus entirely unbiased information on changes of cell morphology that are unequivocally associated with cell death, the latter requires predefined exposure times and a strict causality between metabolic activity and cell death. However, MTT assays are based on standard lab equipment and provide a more economic way to higher throughput.
Institut für Pharmazie, Universität Regensburg , Universitätsstraße 31, 93053 Regensburg, Germany.
Beata
B
Kling
Daniel
D
Bücherl
Peter
P
Palatzky
Frank-Michael
FM
Matysik
Michael
M
Decker
Joachim
J
Wegener
Jörg
J
Heilmann
D000818:Animals; D002478:Cells, Cultured / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D005419:Flavonoids / Q000737:chemistry / Q000494:pharmacology*; D006624:Hippocampus / Q000166:cytology; D062385:Hydroxybenzoates / Q000737:chemistry / Q000494:pharmacology*; D051379:Mice; D015394:Molecular Structure; D019906:Nuclear Magnetic Resonance, Biomolecular; D018384:Oxidative Stress / Q000187:drug effects*; D011794:Quercetin / Q000494:pharmacology
D005419:Flavonoids; D062385:Hydroxybenzoates; D011794:Quercetin; C017616:phenolic acid