Quercetin: A Beacon of Hope in the Post-COVID-19 Health Landscape


In a landmark announcement on May 5th, the World Health Organization (WHO) declared the end of the COVID-19 health emergency, three years after the pandemic’s onset. This declaration marks a significant milestone in the global fight against the SARS-CoV-2 virus. However, it’s crucial to understand that this does not signify the end of the pandemic. The aftermath of the virus continues to affect millions worldwide, with long-lasting symptoms persisting even after recovery from the acute phase of the infection.

The Complexity of Persistent COVID

The phenomenon, known as persistent COVID or post-acute sequelae of COVID-19 (PASC), presents a challenging clinical picture. Patients often report a range of symptoms including musculoskeletal pain, chronic fatigue, mood disturbances, and neurocognitive difficulties. Current research lacks effective validated treatments for these persistent symptoms. This multifactorial pathology stems from various factors including:

  • Persistence of SARS-CoV-2 reservoirs in body tissues
  • Immune dysregulation and reactivation of latent pathogens
  • Emergence of viruses like Epstein-Barr or human herpesvirus-6
  • Microbiota disturbances due to SARS-CoV-2
  • Autoimmune responses
  • Microvascular blood coagulation and endothelial dysfunction
  • Dysfunctional signaling in the brainstem and/or vagus nerve

Risk factors exacerbating persistent COVID include diabetes mellitus, sex (predominantly female), ethnicity (notably Latino), socioeconomic status, and prior health conditions. However, a third of persistent COVID patients had no preexisting conditions, highlighting the indiscriminate nature of the virus.

Oxidative Stress in Persistent COVID

Central to understanding persistent COVID is the role of oxidative stress. This condition, characterized by a systemic imbalance in antioxidant mechanisms, leads to oxidative cell damage. SARS-CoV-2 infection triggers a heightened inflammatory and oxidative state, exacerbating mitochondrial oxidative stress and dysfunction. This further disrupts the balance of the intestinal microbiota, fuelling a vicious cycle of inflammation and oxidative response.

The Role of Quercetin in Managing Persistent COVID

Amidst the search for effective treatments, Quercetin, a natural flavonoid found in many plants and foods, emerges as a promising agent. Quercetin’s antioxidant, anti-inflammatory, and antiviral properties make it a potential therapeutic agent in managing persistent COVID symptoms and complications. Studies have shown its effectiveness in inhibiting various viruses, including SARS-CoV-2, by interfering with virus replication and enhancing the body’s immune response.

Dietary Sources and Bioavailability of Quercetin

Quercetin is naturally present in foods like grapes, red onions, broccoli, grapefruit, apples, cherries, green tea, and red wine. However, factors like the part of the plant, seasonal variations, maturity, and food preparation can affect its concentration. The bioavailability of Quercetin is a challenge, with poor solubility and limited transport across biological barriers being significant obstacles.

Nanotherapy: A Future Direction

To overcome these limitations, nanotherapy presents a promising avenue. The use of nanocarriers, both organic and inorganic, offers enhanced delivery, stability, and controlled release of Quercetin, potentially maximizing its therapeutic effects.


As we reflect on the journey through the COVID-19 pandemic and its aftermath, it becomes increasingly clear that the prevalence of persistent COVID symptoms is a significant public health concern. The role of oxidative stress in this context is crucial, acting as a key factor in the progression of this pathology. The body’s natural response to such stress involves neutralizing harmful free radicals, and herein lies the potential of antioxidants like quercetin.

The past few decades have seen a surge in the consumption of substances with antioxidant properties. Quercetin, in particular, stands out for its wide range of health benefits. This increase in consumption can be attributed to both dietary sources and the use of food supplements. Foods rich in quercetin, such as fruits, vegetables, and certain beverages, contribute to its intake, but supplements offer higher concentrations, potentially enhancing its therapeutic effects.

Quercetin’s multifaceted role in combating the effects of COVID-19 is noteworthy. It has been shown to reduce viral load, decrease the release of pro-inflammatory cytokines, reduce reactive oxygen species (ROS), and decrease mucus production. These actions collectively enhance the resistance of the respiratory tract to infections. Furthermore, quercetin’s safety profile is reassuring; studies have not reported harmful effects in humans at doses up to 1,500 mg per day.

In summary, quercetin emerges as a promising agent in the ongoing battle against persistent COVID symptoms. Its antioxidant properties, coupled with its antiviral and anti-inflammatory effects, make it a valuable component in the management of post-COVID-19 complications. As research continues to evolve, the potential for quercetin to play a significant role in improving the quality of life for those affected by persistent COVID remains a hopeful prospect.

reference link : https://www.frontiersin.org/articles/10.3389/fnut.2023.1278039/full


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