Quercetin — An Various to Hydroxychloroquine, and Extra

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

Half 12 begins with a short overview of what quercetin is and its fundamental mechanisms of motion. Quercetin is a flavonoid present in a wide range of vegetables and fruit, comparable to 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 gentle publicity, although, so relying on the nation you’re in, totally different meals will prime the checklist of most quercetin-rich. Basic mechanisms of motion of this nutrient embrace:3

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

Anti-inflammatory exercise — That is partially chargeable 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 in opposition to 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 combat in opposition to 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 stop viral entry into the cell. Commenting on one in every of these research, Fashionable Discontent notes:8

“Though [a] laptop modeled examine,9 the proof right here means that quercetin’s binding exercise to ACE2 is similar to different normal 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 parts.)

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

Stabilize mast cells and regulate the essential purposeful 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 also 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 elementary to controlling homeostasis on the mobile stage. There may be proof that it down-regulates the flexibility a cell has to generate Kind 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 sort 1 interferon by figuring out the replication of RNA viruses, comparable to 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 in opposition to viruses. There are two sorts and three types of interferon. Inside Kind 1 interferon, there are alpha and beta. Kind 2 interferon has the gamma type.18

The differing types are primarily based on the operate of the cytokine. Kind 1 interferons assist cells resist viruses. Kind 2 aids in responding to infections and most cancers progress. The identify “interferon” got here from the flexibility of Kind 1 to intrude 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 operate 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 Kind 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 in opposition to SARS-CoV20,21,22 — Quercetin’s common antiviral capability has been attributed to a few main 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. Decreasing contaminated cells’ resistance to remedy with antiviral remedy

Inhibit the SARS-CoV-2 predominant protease.24

The Entrance Line Essential COVID-19 Care Alliance (FLCCC) early remedy protocol25 contains 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 a few of the scientific 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 counsel that over-the-counter, simply accessible compounds could also be extraordinarily useful in preventing in opposition to COVID, particularly when taken as a prophylactic.”

In one other trial,29 76 outpatients who examined optimistic however had solely delicate 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 normal care (analgesics, oral steroids and antibiotics). One other 76 sufferers got normal of care solely.

Within the quercetin group, solely 9.2% of members went on to require hospitalization, in comparison with 28.9% of sufferers who acquired normal 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 items and in variety of deaths.

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

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

The second evaluate article,33 revealed within the June 19, 2020, difficulty of Frontiers in Immunology, highlighted quercetin’s usefulness as a COVID-19 remedy when used along side 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 weight loss plan. Quercetin, being present in recent fruits, greens and berries is one in every of them. Sadly, whereas important nutritional vitamins and minerals are usually acknowledged for his or her significance, antioxidants comparable to quercetin are sometimes missed, and generally labeled as “pseudoscience” or “fad” dietary supplements. As famous by Fashionable Discontent:

“The good variety of advantages that these compounds contribute to people can’t be overstated … An argument may be made that not solely may quercetin show useful 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 fundamental well being and a wholesome immune operate. On this regard, a weight loss plan excessive in recent vegetables and fruit can go a great distance. Dietary dietary supplements even have their place, particularly in conditions like a pandemic.


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

“There’s proof that quercetin may go equally to hydroxychloroquine — Plainly 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 a few of the most nicely studied compounds, with potential anti-cancer, pro-heart and pro-organ advantages. Add on potential antimicrobial properties and it turns into onerous 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 in opposition to SARS-CoV2 — Pc fashions and in vitro research counsel that ACE2 receptors and the primary protease of SARS-CoV2 could also be good goal candidates for quercetin … the restricted variety of research counsel 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 regularly … Fashionable ‘enriched’ meals are likely to complement with extra nutritional vitamins and minerals, however might miss out on different plant-derived compounds which have performed a considerable position in our weight loss plan.

Much like diminished daylight publicity and the necessity for elevated vitamin D supplementation, we may have to take a look at potential supplementation of missed compounds comparable to polyphenols. Sourcing these compounds from actual meals would show essentially the most useful, however in teams of people that might not have entry to recent vegetables and fruit, quercetin and polyphenol supplementation could also be helpful.

This would come with folks with various diets comparable to 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 many who could also be lacking out on it of their weight loss plan they might need to look into sourcing it with supplementation. Don’t take this as a prescription or suggestion, however an argument to look at your personal well being and see what you might be missing …”

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