Quercetin — An Various to Hydroxychloroquine, and Extra

The Substack Fashionable Discontent just lately posted an anthology collection on the advantages of quercetin,1 together with the discovering that it really works like hydroxychloroquine, a drug discovered to be efficient towards SARS-CoV-2 when used early sufficient.

Half 12 begins with a quick overview of what quercetin is and its primary mechanisms of motion. Quercetin is a flavonoid present in quite a lot of vegatables and fruits, reminiscent of onions and shallots, apples, broccoli, asparagus, inexperienced peppers, tomatoes, crimson leaf lettuce, strawberries, raspberries, blueberries, cranberries, black currants and inexperienced tea.

The quercetin content material in any given meals is essentially depending on mild publicity, although, so relying on the nation you’re in, completely different meals will prime the checklist of most quercetin-rich. Normal mechanisms of motion of this nutrient embody:3

Antioxidant exercise — Antioxidants assist forestall oxidative harm from dangerous reactive oxygen species (ROS). Quercetin acts as a free radical scavenger, and its exercise will be additional enhanced by vitamin C

Anti-inflammatory exercise — That is partially accountable for quercetin’s cardiovascular advantages

Inhibition of platelet aggregation

Anti-allergy actions (inhibits launch of histamine and different allergic substances)


Anticancer exercise

Antiviral exercise — It’s been discovered to cut back replication of many viruses, together with HIV, hepatitis C, enterovirus 71, porcine epidemic diarrhea virus and SARS-CoV-2, by concentrating on the proteases in these viruses

Zinc ionophore — Quercetin helps zinc enter your cells. Zinc, in flip, has potent antiviral exercise

Quercetin Towards SARS-CoV-2

In Half 24 of the anthology, Fashionable Discontent evaluations the proof behind the advice to make use of quercetin towards COVID-19 particularly. As talked about, zinc has antiviral exercise, and quercetin helps shuttle the zinc into the cell. However quercetin additionally has different mechanisms of motion that make it helpful within the battle towards COVID-19.

For instance, quercetin has been proven to:

Inhibit SARS-CoV-2 spike protein to ACE2 receptor docking.5,6,7 Computational modeling research have proven quercetin can bind to the ACE2 receptor and the spike protein interface, thereby inhibiting the 2 from binding collectively. By stopping viral attachment, it helps forestall viral entry into the cell. Commenting on certainly one of these research, Fashionable Discontent notes:8

“Though [a] pc modeled examine,9 the proof right here means that quercetin’s binding exercise to ACE2 is akin to different commonplace of care medicine used to deal with SARS-CoV-2 (eg. Remdesivir, Lopinavir, Ritonavir).”

Inhibit lipopolysaccharide (LPS)-induced tumor necrosis issue α (TNF-α) manufacturing in macrophages.10 (TNF-α is a cytokine concerned in systemic irritation, secreted by activated macrophages, a kind of immune cell that digests overseas substances, microbes and different dangerous or broken elements.)

Inhibit the discharge of proinflammatory cytokines and histamine by modulating calcium inflow into the cell.11

Stabilize mast cells and regulate the fundamental practical properties of immune cells, thereby permitting it to inhibit “an enormous panoply of molecular targets within the micromolar focus vary, both by down-regulating or suppressing many inflammatory pathways and features.”12

Act as a zinc ionophore, i.e., a compound that shuttles zinc into your cells.13 This is without doubt one of the mechanisms that may account for the effectiveness seen with hydroxychloroquine, which can be a zinc ionophore.

Enhance interferon response to viruses, together with SARS-CoV-2, by inhibiting the expression of casein kinase II (CK2)14 — CK2 is an enzyme that’s basic to controlling homeostasis on the mobile degree. There’s proof that it down-regulates the flexibility a cell has to generate Sort 1 interferon when attacked by a virus.

It does this by inhibiting retinoic acid-inducible gene I (RIG-I),15 which has protein sensors that sign genetic expression of kind 1 interferon by figuring out the replication of RNA viruses, reminiscent of SARS-CoV-2. Quercetin inhibits the expression of CK2, which slows the replication of RNA viruses.16

Interferons are a subset of cytokines found in 1957.17 These cells are sometimes the preliminary protection towards viruses. There are two varieties and three types of interferon. Inside Sort 1 interferon, there are alpha and beta. Sort 2 interferon has the gamma type.18

The differing types are primarily based on the perform of the cytokine. Sort 1 interferons assist cells resist viruses. Sort 2 aids in responding to infections and most cancers development. The identify “interferon” got here from the flexibility of Sort 1 to intervene with the virus’s capability to duplicate. A cell secretes interferons when a overseas substance, like a virus, is detected.

Nonetheless, the interferon doesn’t perform by attacking the virus. As a substitute, it tells the contaminated cell and the cells that encompass the contaminated cell to make proteins that cease viral replication. In a nutshell, quercetin stops CK2 from interfering with the motion of Sort 1 interferon so cells obtain the sign to cease viral replication.

Modulate NLRP3 inflammasome, an immune system element concerned within the uncontrolled launch of proinflammatory cytokines that happens throughout a cytokine storm.19

Exert a direct antiviral exercise towards SARS-CoV20,21,22 — Quercetin’s normal antiviral capability has been attributed to a few major mechanisms of motion:

  1. Binding to the spike protein, thereby inhibiting its capability to contaminate host cells23
  2. Inhibiting replication of already contaminated cells
  3. Lowering contaminated cells’ resistance to therapy with antiviral medicine

Inhibit the SARS-CoV-2 fundamental protease.24

The Entrance Line Crucial COVID-19 Care Alliance (FLCCC) early therapy protocol25 consists of quercetin at a dose of 250 milligrams twice a day, together with 100 mg elemental zinc and 500 mg to 1,000 mg of vitamin C twice a day.

Quercetin in COVID-19 Medical Literature

In Half 3,26 Fashionable Discontent evaluations among the medical trials which have taken place. One COVID-19-specific examine27 discovered that individuals who took zinc and two zinc ionophores — quinine drops and quercetin — had decrease incidence of COVID-19 than the management group. Over the course of the examine (20 weeks), solely two of the 53 check topics grew to become symptomatic, in comparison with 12 of the 60 controls. As famous by Fashionable Discontent:28

“Though this didn’t check quercetin in isolation, the examine does recommend that over-the-counter, simply accessible compounds could also be extraordinarily helpful in combating towards COVID, particularly when taken as a prophylactic.”

In one other trial,29 76 outpatients who examined constructive however had solely gentle signs got 1,000 mg of Quercetin Phytosome® (quercetin in sunflower phospholipids that enhance oral absorption 20-fold) per day for 30 days, along with commonplace care (analgesics, oral steroids and antibiotics). One other 76 sufferers got commonplace of care solely.

Within the quercetin group, solely 9.2% of contributors went on to require hospitalization, in comparison with 28.9% of sufferers who obtained commonplace of care solely. In accordance with the authors:30

“The outcomes revealed a discount in frequency and size of hospitalization, in want of non-invasive oxygen remedy, in development to intensive care models and in variety of deaths.

The outcomes additionally confirmed the very excessive security profile of quercetin and recommended potential anti-fatigue and pro-appetite properties. QP [Quercetin Phytosome®] is a secure agent and together with commonplace care, when utilized in early stage of viral an infection, might help in bettering the early signs and assist in stopping the severity of COVID-19 illness.”

Quercetin was additionally featured in two scientific evaluations printed in 2020.31 The primary, printed in within the Integrative Medication journal in Could 2020,32 highlighted quercetin’s promotion of SIRT2, which inhibits NLRP3 inflammasome.

The second evaluate article,33 printed within the June 19, 2020, subject of Frontiers in Immunology, highlighted quercetin’s usefulness as a COVID-19 therapy when used along with vitamin C. The vitamin C recycles oxidized quercetin, producing a synergistic impact. It additionally enhances quercetin’s antiviral capability.

Meals as Medication

With the arrival of processed meals, many vital vitamins have been misplaced or minimized within the common individual’s food regimen. Quercetin, being present in contemporary fruits, greens and berries is certainly one of them. Sadly, whereas important nutritional vitamins and minerals are usually acknowledged for his or her significance, antioxidants reminiscent of quercetin are sometimes neglected, and typically labeled as “pseudoscience” or “fad” dietary supplements. As famous by Fashionable Discontent:

“The nice variety of advantages that these compounds contribute to people can’t be overstated … An argument will be made that not solely might quercetin show helpful to our well being, however an absence of it might show detrimental in the long run.”

If COVID-19 has taught us something, it’s the significance of primary well being and a wholesome immune perform. On this regard, a food regimen excessive in contemporary vegatables and fruits can go a great distance. Dietary dietary supplements even have their place, particularly in conditions like a pandemic.


In conclusion, Fashionable Discontent offers the next abstract of findings:34

“There’s proof that quercetin may fit equally to hydroxychloroquine — It appears that evidently quercetin might function as each an immunomodulator and a zinc ionophore. Its use as an over-the-counter anti-allergic complement in addition to its use for bronchial asthma signifies a capability to have an effect on the manufacturing of histamine and cytokines …

Quercetin has loads of different advantages — … Antioxidants … are among the most properly studied compounds, with potential anti-cancer, pro-heart and pro-organ advantages. Add on potential antimicrobial properties and it turns into arduous to argue that that is nothing greater than a potential fad complement.

Though restricted, there may be some proof that quercetin could also be efficient towards SARS-CoV2 — Laptop fashions and in vitro research recommend that ACE2 receptors and the primary protease of SARS-CoV2 could also be good goal candidates for quercetin … the restricted variety of research recommend quercetin could also be efficient, particularly if used early on or as a prophylactic.

Dietary quercetin is the primary supply of quercetin, and its deficiency in fashionable diets could also be contributing to our well being issues — Quercetin is primarily sourced from colourful fruits, greens, teas … all meals that lots of our ancestors would have consumed frequently … Fashionable ‘enriched’ meals are likely to complement with further nutritional vitamins and minerals, however might miss out on different plant-derived compounds which have performed a considerable function in our food regimen.

Just like diminished daylight publicity and the necessity for elevated vitamin D supplementation, we may have to have a look at potential supplementation of neglected compounds reminiscent of polyphenols. Sourcing these compounds from actual meals would show probably the most helpful, however in teams of people that might not have entry to contemporary vegatables and fruits, quercetin and polyphenol supplementation could also be helpful.

This would come with folks with different diets reminiscent of keto, who might keep away from excessive carb fruits, and thus could also be lacking a key nutrient of their diets.

Quercetin has loads of advantages, and for individuals who could also be lacking out on it of their food regimen they could wish to look into sourcing it with supplementation. Don’t take this as a prescription or advice, however an argument to look at your personal well being and see what you might be missing …”

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