Quercetin, A Natural Phytochemical

By: Dr. Magdy Badran

Quercetin is one of the most common and well-researched flavonoids. It is a pigment in many plants, fruits, and vegetables.

What is Quercetin?

Quercetin is a flavonol, which is a sub-category of flavonoids. Flavonoids are phytochemical compounds in plants, fruits, herbs, vegetables and nuts.

Quercetin pigments give many fruits, flowers, and vegetables their colors. It is known for its anti-inflammatory, antihypertensive, vasodilator effects, antiobesity, antihypercholesterolemic and antiatherosclerotic activities.

Quercetin is a Powerful Antioxidant

Quercetin is a polyphenolic flavonoid compound. Modern studies have shown that quercetin prevents various diseases, such as osteoporosis, some forms of cancer, tumors, and lung and cardiovascular diseases. The antioxidant effects of quercetin play a significant role in the prevention and treatment of such diseases.

Quercetin is a more powerful antioxidant than vitamin C, E, or beta carotene. The antioxidant activity of quercetin is mainly manifested through its effect on glutathione, enzymatic activity, signal transduction pathways, and reactive oxygen species caused by environmental and toxicological factors. Quercetin shows a strong antioxidant activity by maintaining oxidative balance.

Quercetin increases the body’s antioxidant capacity by regulating levels of glutathione. Quercetin induces glutathione synthesis. Glutathione is an antioxidant, a molecule that helps fight free radicals. Free radicals are unstable molecules that form in response to factors like your diet and the environment. Free radicals are unstable molecules in the body that can increase the risk of disease and quicken aging. The body produces free radicals through regular metabolic processes such as energy production. However, different external factors can contribute to free radical production, including: pollution, cigarette smoke, radiation, sun exposure, stress, alcohol consumption, chemical toxins and greenhouse gases. When more free radicals than antioxidants are present, oxidative cell damage occurs. This can lead to inflammation and a variety of health issues ranging from high blood pressure and diabetes to Alzheimer's disease and more.

In addition to being an antioxidant, glutathione also plays a part in your body's: metabolism of toxins and cancer-causing substances, natural creation and repair of DNA, production of protein and prostaglandin, a compound with hormone-like effects and activation of enzymes. Glutathione is involved in tissue building and repair, making chemicals and proteins needed in the body, and in immune system function.

The Anti-inflammatory Activities of Quercetin

Inflammation is the body’s natural response to stress and injuries and usually helps the body heal. However, chronic inflammation can harm the body and contribute to specific health conditions. Chronic inflammation continues sending inflammatory cells even when there is no outside danger. Chronic inflammation may be caused by infections that don’t go away, abnormal immune reactions to normal tissues, or conditions such as obesity. Over time, chronic inflammation can cause DNA damage and may lead to cancer.

Quercetin was reported as a long lasting anti-inflammatory substance that possesses strong anti-inflammatory capacities. It possesses anti-inflammatory potential that can be expressed on different cell types, both in animal and human models.

Neuroprotective Effects of Quercetin

Quercetin may reduce the risk of neurodegenerative diseases, such as Alzheimer’s or Parkinson’s disease. Several studies show that quercetin can exert neuroprotection and antagonize oxidative stress when administered in vivo. Oxidative stress contributes to the development of neurodegenerative diseases. The antioxidant properties of quercetin may help fight free radicals.

A Naturally Occurring Anti-Allergic Compound

In test tubes, quercetin prevents immune cells from releasing histamines, which are chemicals that cause allergic reactions. As a result, researchers think that quercetin may help reduce symptoms of allergies, including runny nose, watery eyes, hives, and swelling of the face and lips.

Quercetin inhibits the release of histamine and other inflammatory mediators. Studies indicate that it works better than Cromolyn, an old asthma medication with some nasty side effects. The good news about quercetin is it is very well-tolerated.

Because of similar inflammatory pathways that affect asthmatics and patients with urticaria eczema, quercetin can also have potential benefits for that patient population.

Cardioprotective Effects of Quercetin

Diet plans consisting of flavonoids such as quercetin have positive health benefits, especially on the heart. Flavonoids have been proven to be active against hypertension, inflammation, diabetes and vascular diseases. Quercetin exhibits significant heart related benefits as regulation of lipid metabolism , endothelium-independent vasodilator effects, reduction of adhesion molecules and other inflammatory markers, the protective effect on nitric oxide and endothelial function under conditions of oxidative stress, prevention of neuronal oxidative and inflammatory damage and platelet antiaggregant effects.

Quercetin and its derivatives lead to an enhancement in heart features, indicating the prospective for quercetin to be used therapeutically in the treatment of cardiac diseases. Several evidence-based studies suggest mechanisms to observe cardiovascular diseases such as aging effects, hypertension, angiotensin-converting enzyme activity and endothelial-dependent and independent functions. Taking quercetin supplements could be an effective way to reduce blood pressure.

Foods High in Quercetin

Onions are amongst the richest sources of quercetin.

Quercetin is abundant in nature and foods. Quercetin is found naturally in many plant-based foods, particularly in the outer layer or peel. Good food sources include: peppers, onions, asparagus, cherries, tomatoes, red apples, red grapes, broccoli, red leaf lettuce, nuts, seeds, olive oil and berries — all types.