Could the flavonoid quercetin be used to treat coronavirus?

I hesitate to add another article to the insanely large volume of reading material already connected with COVID-19. However, I’ll share my thoughts in case they spark an idea, because I’ve noticed a lot of that happening these days.

You’ve probably heard by now of the drug hydroxychloroquine (HCQ) that has been under investigation for treatment of Coronavirus Disease 2019 (COVID-19). Recommendations from Chinese doctors to employ it (the initial recommendation, on Feb 18 was to employ chloroquine phosphate, a related drug) were followed by a small-scale study from French researchers, published on March 20, which was promising but not definitive. On March 25, a Chinese study reported that HCQ did not have a significant benefit to patients, but the validity of that 30-patient study has since been questioned as it turned out that both the HCQ and control groups were also receiving other antiviral treatments. The majority of patients in that study made good recoveries so it’s hard to say whether HCQ was useful or not, and overall the jury is still out on HCQ.

Let food be thy medicine

The importance of zinc

“In developing countries, zinc deficiency is the 5th leading cause for the loss of healthy life years. In industrial countries, mainly the elderly population is affected by zinc deficiency.”

Personally, I’ll be relying mainly on food sources for my zinc supply, such as seeds, legumes, mushrooms and spinach. But there’s one other important factor besides getting zinc into our bodies and that’s getting it into the cells that are threatened by coronavirus.

Hydroxychloroquine is a zinc ionophore

Now, it must be pointed out that this is all pretty hypothetical. The facts are that zinc was shown in vitro to inhibit coronavirus replication and that HCQ is a zinc ionophore. But it’s still uncertain that HCQ will be effective against coronavirus and even if it is, the mechanism may not even be zinc-related. Medicine is complex and a drug can have many different impacts on the body. The authors of the 2014 paper that established that HCQ can act as a zinc ionophore point out that:

“Chloroquine exerts a pleiotropic effect in eukaryotic cells, including an elevation of vacuolar pH when trapped in acidic organelles, such as lysosomes.”

Raising the pH of lysosomes is one of the main hypotheses for the mechanism of action of HCQ. The action of raising the pH may be somewhat related to HCQs property as an ionophore as they both involve the movement of ions across membranes.

In the next video, following up on the theory that the mechanism of HCQ could be zinc-related, Dr. Seheult raises the question: Are there other zinc ionophores that could work?

And that’s where quercetin comes in.

Two zinc ionophores: the synthetic antimalarial drug, hydroxychloroquine (left) and the naturally occurring flavonoid, quercetin.

Quercetin — a naturally occurring zinc ionophore.

“Dietary plant polyphenols such as the flavonoids quercetin (QCT) and epigallocatechin-gallate act as antioxidants and as signaling molecules. Remarkably, the activities of numerous enzymes that are targeted by polyphenols are dependent on zinc. We have previously shown that these polyphenols chelate zinc cations and hypothesized that these flavonoids might be also acting as zinc ionophores, transporting zinc cations through the plasma membrane.”

If HCQ proves to be effective in treating COVID-19 then it’s possible that quercetin in our diet may also be protective (while avoiding the side effects of HCQ). But that’s also predicated on quercetin having a similar effect to HCQ in patients and again, medicine is complex.

Quercetin — other ways that it may be helpful in treating COVID-19

· In 2015 it was reported that quercetin inhibits entry of the influenza A and the H5N1 virus to cells in vitro.

· Quercetin was also found to inhibit adhesion of the human respiratory syncytial virus (hRSV).

· Researchers from Oak Ridge National Lab used the world’s most powerful supercomputer, SUMMIT, to look for small molecules that might inhibit the COVID-19 spike protein from interacting with human cells and interestingly, quercetin is fifth on that list.

· This is not a peer-reviewed scientific publication but Dr. Leo Galland also recommends quercetin, but via a different mechanism (mTOR modulation). Incidentally, his other recommendations can also be obtained from food sources: curcumin (turmeric), rosmarinic acid (rosemary, sage, oregano), resveratrol (red wine and grapes), and elderberry.

So it boils down to two possible benefits from quercetin: modulation of zinc transport into cells (and possibly altering the pH in lysosomes) and blocking viral docking to host cells.

Bottom line: should you eat quercetin-rich foods?

Check out the Green Stars Project for more articles on health, and specifically on how ethical consumerism relates to health.

User-generated ratings for ethical consumerism. Mission: to encourage consideration of the social and environmental impact of our choices as consumers.

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