Nothing quite compares to a tasty, fresh, crisp apple, but most people might not know that apples contain a very interesting compound that has a number of potential health benefits.

History of quercetin

Quercetin is a naturally occurring member of the flavonoid family – a large family of water-soluble chemicals that are not created by the body and are an important part of a healthy diet. Flavonoids were discovered back in 1936, when Albert Szent-Györgyi, an American biochemist born in Hungary, was researching ways to treat scurvy.

Albert Szent-Györgyi went on to win the Nobel Prize in Physiology or Medicine in 1937 “for his discoveries in connection with the biological combustion processes, with special reference to vitamin C and the catalysis of fumaric acid”.

We have much to thank him for, especially for his discovery of the flavonoids and, in particular, quercetin. During the late 1930s to 1950s, flavonoids were commonly referred to as vitamin P, as in permeability, indicating their ability to influence the permeability of blood vessel walls.

Quercetin in nature

Quercetin is naturally found in some fruit and vegetables, such as apples, onions, and dark cherries. Whole apples contain around 4.4 milligrams of quercetin for every 100 grams of apple. A medium-sized apple is typically about 150 grams, so apples could contain up to 10 milligrams of quercetin each.

To get a typical dose (around 500 mg) used for health purposes, you would need to eat at least 50 apples a day! So, unless you really like apples, eating enough to gain health benefits from quercetin is completely out of the question.

Thankfully, there is a solution to this problem: quercetin is available as a supplement. Quercetin is a relatively inexpensive supplement and is readily available from a variety of sources.

In the interests of impartiality, we cannot recommend a particular brand or supplier, but needless to say, you will be spoiled for choice, as there are many places to obtain quercetin on the Internet.

Isoquercetin (also known as isoquercitrin) is a less common, naturally occurring glucoside of quercetin, which has the same benefits as regular quercetin has but has better bioavailability and absorption by the body, making it more effective than quercetin [1]. It is harder to obtain than regular quercetin and may be more expensive, though it does require smaller amounts, being around 6 times more potent.

Potential health benefits

In studies, quercetin has demonstrated antioxidant properties by neutralizing oxygen free radicals and reactive molecules of nitrogen [2-3]. Various studies have shown that quercetin has anti-bacterial [4-5], anti-inflammatory [6], and anti-carcinogenic [7-12] properties.

Some other studies show that quercetin has the ability to enhance proteolysis and maintain proteostasis [13-14]. A study demonstrated that, by enriching the diet of aged mice with quercetin, an increase in exploratory behavior and improvement in general and spatial awareness are seen [15]. An additional study showed an improvement of the immune cells of artificially aged mice [16].

Research has shown that a topical quercetin treatment increases the hydration and elasticity of the skin, reducing wrinkles [17]. Quercetin has also shown efficacy in treating skin disorders like dermatitis [18-20].

NAD+ is found in all of our cells, interacts with sirtuins to mediate metabolism, and plays a role in health and lifespan. Quercetin has been shown to be of benefit in reducing inflammation and in increasing NAD+ levels through inhibiting inflammatory factors such as CD38, which increases with age and destroys NAD+, reducing energy levels as we get older [21-23].

As we age, increasing amounts of dysfunctional, non-dividing senescent cells accumulate; normally, these damaged cells are removed by the immune system, but, as we age, this system declines and more and more of these cells build up. Quercetin can potentially influence this aging process directly, removing senescent cells by inducing apoptosis.

Senescent cells cause chronic levels of inflammation and an altered intracellular signaling environment through a cocktail of inflammatory cytokines, chemokines, and proteins known collectively as the senescence-associated secretory phenotype, or SASP [24]. The resulting inflammation is believed to be one of the drivers of the aging process [25-26], and subsequent studies have suggested that quercetin reduces inflammation by inhibiting some elements of the SASP or by directly inducing apoptosis when used in combination with other drugs to improve vascular health [27-28].

Quercetin may prove useful to remove these cells and keep us healthier for longer. Finally, quercetin has shown promise in reducing blood pressure, with a number of tests showing positive results for people with hypertension [29]. A detailed meta-analysis on quercetin and blood pressure was also conducted [30].


This article is only a very brief summary. It is not intended as an exhaustive guide and is based on the interpretation of research data, which is speculative by nature. This article is not a substitute for consulting your physician about which supplements may or may not be right for you. We do not endorse supplement use or any product or supplement vendor, and all discussion here is for scientific interest.


[1] Paulke, A., Eckert, G. P., Schubert-Zsilavecz, M., & Wurglics, M. (2012). Isoquercitrin provides better bioavailability than quercetin: comparison of quercetin metabolites in body tissue and brain sections after six days administration of isoquercitrin and quercetin. Die Pharmazie-An International Journal of Pharmaceutical Sciences, 67(12), 991-996.

[2] Hanasaki, Y., Ogawa, S., Fukui, S. (1994). The correlation between active oxygens scavenging and antioxidative effects of flavonoids. Free Radical Biology and Medicine, 16(6), 845-850.

[3] Van Acker, S. A., et al. (1996). Structural aspects of antioxidant activity of flavonoids. Free Radical Biology and Medicine, 20(3), 331-342.

[4] Boots, A. W., Haenen, G. R., Bast, A. (2008). Health effects of quercetin: from antioxidant to nutraceutical. European Journal of Pharmacology, 585(2), 325-337.

[5] Cushnie, T. T., Lamb, A. J. (2005). Antimicrobial activity of flavonoids. International Journal of Antimicrobial Agents, 26(5), 343-356.

[6] Sen, G., Biswas, D., Ray, M., Biswas, T. (2007). Albumin–quercetin combination offers a therapeutic advantage in the prevention of reduced survival of erythrocytes in visceral leishmaniasis. Blood Cells, Molecules, and Diseases, 39(3), 245-254.

[7] Oršolić, N., et al. (2004). Immunomodulatory and antimetastatic action of propolis and related polyphenolic compounds. Journal of Ethnopharmacology, 94(2), 307-315.

[8] Gulati, N., et al. (2006). The antiproliferative effect of Quercetin in cancer cells is mediated via inhibition of the PI3K-Akt/PKB pathway. Anticancer Research, 26(2A), 1177-1181.

[9] Kuo, S. M. (1996). Antiproliferative potency of structurally distinct dietary flavonoids on human colon cancer cells. Cancer Letters, 110(1), 41-48.

[10] Landis‐Piwowar, K. R., Milacic, V., Dou, Q. P. (2008). Relationship between the methylation status of dietary flavonoids and their growth‐inhibitory and apoptosis‐inducing activities in human cancer cells. Journal of Cellular Biochemistry, 105(2), 514-523.

[11] Oršolić, N., et al. (2004). Immunomodulatory and antimetastatic action of propolis and related polyphenolic compounds. Journal of Ethnopharmacology, 94(2), 307-315.

[12] Zamin, L. L., et al. (2009). Resveratrol and quercetin cooperate to induce senescence‐like growth arrest in C6 rat glioma cells. Cancer Science, 100(9), 1655-1662.

[13] Trougakos, I. P., et al. (2003). Slowing down cellular aging in vitro. Modulating Aging and Longevity Kluwer Academic Publishers, 65-83.

[14] Chondrogianni, N., et al. (2010). Anti-ageing and rejuvenating effects of quercetin.Experimental Gerontology, 45(10), 763-771.

[15] Liu, J., Yu, H., Ning, X. (2006). Effect of quercetin on chronic enhancement of spatial learning and memory of mice. Science in China Series C: Life Sciences,49(6), 583-590.

[16] Álvarez, P., et al. (2006). Improvement of leukocyte functions in prematurely aging mice after five weeks of diet supplementation with polyphenol-rich cereals. Nutrition,22(9), 913-921.

[17] Nebus, J., Vassilatou, K., Philippou, L., Wallo, W. (2011). Clinical improvements in facial photoaged skin using a novel oak quercetin topical preparation. Journal of the American Academy of Dermatology, 64(2): AB73-AB73.

[18] Jung, M. K., Hur, D. Y., Song, S. B., Park, Y., Kim, T. S., Bang, S. I., … & Cho, D. H. (2010). Tannic acid and quercetin display a therapeutic effect in atopic dermatitis via suppression of angiogenesis and TARC expression in Nc/Nga mice. Journal of Investigative Dermatology, 130(5), 1459-1463.

[19] Weng, Z., Zhang, B., Asadi, S., Sismanopoulos, N., Butcher, A., Fu, X., … & Theoharides, T. C. (2012). Quercetin is more effective than cromolyn in blocking human mast cell cytokine release and inhibits contact dermatitis and photosensitivity in humans. PLoS One, 7(3), e33805.

[20] Karuppagounder, V., Arumugam, S., Thandavarayan, R. A., Sreedhar, R., Giridharan, V. V., & Watanabe, K. (2016). Molecular targets of quercetin with anti-inflammatory properties in atopic dermatitis. Drug discovery today, 21(4), 632-639.

[21] Escande, C., Nin, V., Price, N. L., Capellini, V., Gomes, A. P., Barbosa, M. T., … & Chini, E. N. (2013). Flavonoid Apigenin Is an Inhibitor of the NAD+ ase CD38 Implications for Cellular NAD+ Metabolism, Protein Acetylation, and Treatment of Metabolic Syndrome. Diabetes, 62(4), 1084-1093.

[22] Camacho-Pereira, J., Tarrago, M. G., Chini, C. C., Nin, V., Escande, C., Warner, G. M., … & Chini, E. N. (2016). CD38 dictates age-related NAD decline and mitochondrial dysfunction through an SIRT3-dependent mechanism. Cell metabolism, 23(6), 1127-1139.

[23] Schultz, M. B., & Sinclair, D. A. (2016). Why NAD+ Declines during Aging: It’s Destroyed. Cell metabolism, 23(6), 965-966.

[24] Coppé, J. P., Desprez, P. Y., Krtolica, A., & Campisi, J. (2010). The senescence-associated secretory phenotype: the dark side of tumor suppression. Annual review of pathology, 5, 99.

[25] López-Otín, C., Blasco, M. A., Partridge, L., Serrano, M., & Kroemer, G. (2013). The hallmarks of aging. Cell, 153(6), 1194-1217.

[26] van Deursen, J. M. (2014). The role of senescent cells in ageing. Nature, 509(7501), 439-446.

[27] Zhu, Y., Tchkonia, T., Pirtskhalava, T., Gower, A. C., Ding, H., Giorgadze, N., … & O’Hara, S. P. (2015). The Achilles’ heel of senescent cells: from transcriptome to senolytic drugs. Aging cell, 14(4), 644-658.

[28] Roos, C. M., Zhang, B., Palmer, A. K., Ogrodnik, M. B., Pirtskhalava, T., Thalji, N. M., … & Zhu, Y. (2016). Chronic senolytic treatment alleviates established vasomotor dysfunction in aged or atherosclerotic mice. Aging Cell, 15(5), 973-977.

[29] Edwards, R. L., Lyon, T., Litwin, S. E., Rabovsky, A., Symons, J. D., & Jalili, T. (2007). Quercetin reduces blood pressure in hypertensive subjects. The Journal of nutrition, 137(11), 2405-2411.

[30] Serban, M. C., Sahebkar, A., Zanchetti, A., Mikhailidis, D. P., Howard, G., Antal, D., … & Lip, G. Y. (2016). Effects of Quercetin on Blood Pressure: A Systematic Review and Meta‐Analysis of Randomized Controlled Trials. Journal of the American Heart Association, 5(7), e002713.


CategoryBlog, Supplements
About the author

Steve Hill

As a scientific writer and a devoted advocate of healthy longevity and the technologies to promote them, Steve has provided the community with hundreds of educational articles, interviews, and podcasts, helping the general public to better understand aging and the means to modify its dynamics. His materials can be found at H+ Magazine, Longevity reporter, Psychology Today and Singularity Weblog. He is a co-author of the book “Aging Prevention for All” – a guide for the general public exploring evidence-based means to extend healthy life (in press).
  1. June 29, 2017

    There is obviously a bunch to identify about this. I suppose
    you made certain nice points in features also.

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