Zinc ionophore activity of quercetin and epigallocatechin-gallate: from Hepa 1-6 cells to a liposome model.
Level 5 - mechanism / opinion, no new human data
Bench / in vitro mechanistic cell culture and liposome model study
PubMed 25050823 · doi:10.1021/jf5014633
What was done
Researchers tested whether the dietary flavonoids quercetin and epigallocatechin-gallate act as zinc ionophores capable of transporting zinc across lipid bilayers. They assessed labile zinc increases in mouse hepatocarcinoma Hepa 1-6 cells and evaluated transporter-independent transport using cell-free unilamellar dipalmitoylphosphocholine/cholesterol liposomes encapsulating the membrane-impermeant fluorescent zinc indicator FluoZin-3. Liposomes were exposed to quercetin, epigallocatechin-gallate, or the reference chelator clioquinol, alone or combined with zinc cations.
What was found
The abstract reports no numerical values, concentrations, or statistical metrics. Qualitatively, quercetin and epigallocatechin-gallate rapidly elevated labile zinc in Hepa 1-6 cells. In the liposome model, an increase in intra-liposomal FluoZin-3 fluorescence occurred exclusively when chelators (quercetin, epigallocatechin-gallate, or clioquinol) were combined with zinc, demonstrating direct lipid membrane transport.
Why it matters
This establishes a direct biophysical mechanism showing dietary polyphenols can facilitate zinc entry across lipid membranes independently of membrane transporters, providing an explanation for how these compounds influence zinc-dependent signaling pathways.
Limits
The study is entirely in vitro, using synthetic liposome vesicles and a murine cancer cell line, preventing direct extrapolation to in vivo biological activity or human dietary intakes. The abstract provides no quantitative data, kinetics, or dose-response parameters.
Cited by
- supports Quercetin and epigallocatechin gallate (EGCG) function as zinc ionophores that transport zinc cations across cell plasma membranes independently of zinc transporters.