Zinc is a decidedly anti-viral mineral. High intracellular concentrations inhibit the replication of RNA type viruses, such as SARS-CoV-2. Zinc does this by blocking RNA-dependent RNA polymerase (RdRp), the core enzyme of their multiprotein replication and transcription complex that is critical for the copying of viral RNA.
That's the conundrum. In high concentrations, zinc can block coronavirus reproduction, but the cell is typically disinclined to tolerate high levels of zinc due to concerns about its other actions.
Enter the zinc ionophores.
Fortunately, there are molecules that can act as facilitators and enhance the entry of zinc into the cell. These are known as zinc ionophores, and here's the payoff: in addition to its effects on endosome pH, chloroquine has also been demonstrated to be a zinc ionophore.