Quercetin: yes to an active defensive system, no to excess inflammation.

Don’t be surprised if studies to help us fight the new SARS CoV-2 (better known as CoVid-19) often target natural molecules. This time the attention of scientific research has turned the spotlight on a very well-known molecule that is very present in plants, known above all for its antioxidant activity: Quercetin.

What is Quercetin

Quercetin is a molecule of natural origin, one of the most common flavonoids present in abundance in some plants such as calendula and chamomile. It is even possible to find it in some foods such as capers, red onion, radicchio, green tea and red wine.

Quercetin and Covid

This molecule has already been studied in the past for its anti-inflammatory, antioxidant and anti-allergic, antiproliferative and immunomodulating properties. During the new Coronavirus pandemic, it has returned to the attention of several researchers as its components act as inhibitors of the virus itself.
An international study in which a group of researchers from the Institute of Nanotechnology of the National Research Council, the Cnr-Nanotec of Cosenza, took part suggests that Quercetin functions as a specific inhibitor of SARS CoV-2.

Quercetin, according to this study, seems to have a destabilizing action on 3CLpro, one of the fundamental proteins for the replication of the virus, reducing its enzymatic activity. In other words, by interfering with the replication of the virus and reducing cell adhesion to the host, it would appear to have an antiviral action.

Association of Quercetin and other nutraceuticals

This molecule can be associated with other substances indisputably essential to the immune system such as vitamin C, zinc and vitamin D. Not surprisingly, the combination of different substances has made this new supplement performant and unique in its composition.


The association with vitamin C would seem to increase the bioavailability of Quercetin, interrupting the entry, replication and enzymatic activity of the virus and at the same time supporting and strengthening the immune response. The combined administration of Quercetin and Vitamin C is an experimental strategy for the prevention and treatment of various respiratory viruses.


Also in this case we are talking about the synergy of nutraceuticals as Zinc is able to break down inflammation and reduce the link between the virus and its receptor; moreover, it reduces viral replication. But to do this, Zinc needs ionophores that allow greater penetration into the cells: Quercetin is just an ionophore of Zinc.
Therefore this association allows the Zinc to enhance its antiviral action. Furthermore, other studies show that Quercetin finds complementarity with Bromelain, as it strengthens the anti-inflammatory activity by increasing the production of prostaglandins. Taken together, they are therefore an indispensable resource for supporting the immune system.


It is now known that vitamin D is very useful in the prevention and treatment of infections of the upper respiratory tract, as well as in the traditional flu. We cannot say that it has a specific and direct action on the virus, but we know that it is able to support the immune system and therefore make it more efficient against the virus. In addition, it would appear that Quercetin is able to activate the vitamin D receptor, which is why they are associated.

Quercetin Advance

PromoPharma® researchers, following available international studies and supporting evidence, have formulated a new food supplement: Quercetin Advance, based on Quercetin and Bromelain, with Vitamin C, Vitamin D and Zinc that contribute to the normal function of the immune system.

When to take Quercetin Advance:

  • Hypoimmunity
  • Seasonal viral epidemic infections
  • Colds
  • Sinusitis
  • Free radicals
  • Capillary fragility

It is recommended to take 1 capsule per day, during the meal.


Bibliographical references

• Olga Abian et al. Structural stability of SARS-CoV-2 3CLpro and identification of quercetin as an inhibitor by experimental screening. International Journal of Biological Macromolecules 164 (2020) 1693–1703.
• Ruben Manuel Luciano Colunga Biancatelli, Max Berrill, John D. Catravas and Paul E. Marik. Quercetin and Vitamin C: An Experimental, Synergistic Therapy for the Prevention and Treatment of SARS-CoV-2 Related Disease (COVID-19). REVIEW published: 19 June 2020.
• Oghenekome A. Gbinigie 1, Ralph K. Akyea. Should zinc be used for COVID-19 prophylaxis or treatment? A rapid review [version 1; peer review: awaiting peer review]. Wellcome Open Research 2020, 5:188.
• Laila Rigolin Fortunato, Claudiney de Freitas Alves, Maxelle Martins Teixeira, Alexandre Paula Rogerio. Quercetin: a flavonoid with the potential to treat asthma. Brazilian Journal of Pharmaceutical Sciences vol. 48, n. 4, oct./dec., 2012.
• The Study of Quadruple Therapy Zinc, Quercetin, Bromelain and Vitamin C on the Clinical Outcomes of Patients Infected With COVID-19. ClinicalTrials.gov Identifier: NCT04468139.
• Susanne Andres et al. Safety Aspects of the Use of Quercetin as a Dietary Supplement. Mol. Nutr. Food Res. 2018, 62, 1700447.
• Meilan K Han et al. Randomised clinical trial to determine the safety of quercetin supplementation in patients with chronic obstructive pulmonary disease. BMJ Open Resp Res 2020;7.
• Yao Li et al. Quercetin, Inflammation and Immunity. Nutrients 2016, 8, 167.
• Quercetin Directly Interacts with Vitamin D Receptor (VDR): Structural Implication of VDR Activation by Quercetin Ki-Young Lee. Biomol Ther 24(2), 191-198 (2016).
• Monique Aucoin .The effect of quercetin on the prevention or treatment of COVID-19 and other respiratory tract infections in humans: A rapid review. Advances in Integrative Medicine. Article in press.
• Shane D Scholten. Effects of vitamin D and quercetin, alone and in combination, on cardiorespiratory fitness and muscle function in physically active male adults. Open Access Journal of Sports Medicine 2015:6 229–239.

Avatar Di Team Scientifico R&S PromoPharma

Un team di medici qualificati, con oltre 20 anni di esperienza nel settore dell'integrazione alimentare e della fitoterapia, propone articoli e approfondimenti con cognizione scientifica, basandosi su studi clinici pubblicati su riviste internazionali e condotti da istituti riconosciuti.

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