What is Quercetin?
Quercetin is a naturally occurring plant flavonoid found in a variety of fruits, vegetables, leaves, and grains. It belongs to a class of compounds known as polyphenols, specifically the flavonol subgroup, renowned for their antioxidant properties.
It is commonly present in foods such as:
- Onions
- Apples
- Berries
- Grapes
- Citrus fruits
- Broccoli
- Green tea
Quercetin contributes to the pigmentation in plants and plays a role in their defense against environmental stressors.
What Compounds Are in Quercetin?
Quercetin itself is a polyphenolic compound, specifically a flavonoid, characterized by a specific structure made up of:
- Five hydroxyl groups (-OH) that contribute to its antioxidant activity.
- A flavonoid backbone that allows it to scavenge free radicals and chelate metal ions.
In addition to its standalone form, quercetin often exists in nature as glycosides, where sugar molecules are attached to quercetin, enhancing its solubility and bioavailability.
Why Do We Need Quercetin?
The human body is exposed to oxidative stress caused by free radicals, environmental toxins, pollution, and poor lifestyle habits. Oxidative stress contributes to aging, inflammation, and the development of chronic diseases such as:
- Cardiovascular diseases
- Cancer
- Neurodegenerative disorders (e.g., Alzheimer’s)
- Diabetes
Quercetin is valued for its strong antioxidant and anti-inflammatory properties, which help:
- Neutralize free radicals
- Reduce cellular damage
- Support immune function
- Mitigate chronic inflammation
Uses and Benefits of Quercetin
1. Antioxidant Protection
Quercetin combats oxidative stress by scavenging harmful free radicals, thereby protecting cells and tissues from damage.
2. Anti-Inflammatory Effects
It inhibits pro-inflammatory enzymes and cytokines, making it effective in reducing symptoms of inflammation-related conditions like arthritis.
3. Cardiovascular Health
Quercetin helps:
- Lower blood pressure
- Improve endothelial function
- Reduce LDL cholesterol oxidation, a factor in atherosclerosis
4. Immune System Support
It enhances immune response and may help in fighting viral infections, including those caused by rhinoviruses and potentially SARS-CoV-2, by inhibiting viral replication.
5. Anti-Cancer Potential
Research suggests quercetin may have anti-cancer properties by:
- Inducing apoptosis (cell death) in cancer cells
- Inhibiting tumor growth
- Reducing metastasis
6. Neuroprotective Properties
Quercetin may protect neurons against oxidative damage and inflammation, contributing to cognitive health and potentially lowering the risk of neurodegenerative diseases.
7. Exercise Performance
Some studies show quercetin can improve endurance and reduce fatigue by enhancing mitochondrial function and reducing exercise-induced oxidative stress.
References
- Li, Y., Yao, J., Han, C. et al. "Quercetin, Inflammation and Immunity." Nutrients, 2016. https://www.mdpi.com/2072-6643/8/3/167
- Boots, A.W., Haenen, G.R.M.M., Bast, A. "Health effects of quercetin: from antioxidant to nutraceutical." European Journal of Pharmacology, 2008. https://doi.org/10.1016/j.ejphar.2008.03.008
- D'Andrea, G. "Quercetin: A flavonol with multifaceted therapeutic applications?" Fitoterapia, 2015. https://doi.org/10.1016/j.fitote.2015.01.019