A South Korean research paper has demonstrated in Vitro that by increasing the Zinc concentration in cellular cytoplasm, that viral replication is inhibited. As intracellular levels of Zinc are increased the inhibition of viral replication can reach 100% according to charts within the paper.
Like quercetin, epigallocatechin gallate (EGCE) that is also available in capsules. It is a green tea extract. And there could very well be others.
We suggest you look at the video in the comments also.