Flavonoids Secondary plant substances Moleqlar

Flavonoids are a subcategory of polyphenols, which are secondary plant compounds. This group of flavonoids can also be further divided into subcategories: Flavonols, Flavanols, Flavanones, Flavones, Anthocyanins, and Isoflavonoids. Flavonoids are found exclusively in plants and are responsible for the red, blue, light yellow and purple hues found in many fruits and vegetables, including apples, cherries, onions, soy, black and green tea.

The role of flavonoids in plants

Flavonoids play an important role in maintaining the health and vitality of plants. They offer a variety of benefits, some of which we would like to briefly discuss:

UV protection

Flavonoids protect plants from harmful UV rays by acting like a natural sunscreen. This is crucial because overexposure to UV rays can cause cellular damage in plants, affecting their growth and overall health. By absorbing these harmful rays, flavonoids prevent potential damage and allow the plant to thrive.

Pest control

Flavonoids also serve as natural defense mechanisms against pests and diseases. They have a deterrent effect and make the plant unattractive to various insects and pests. They also have antimicrobial properties that protect the plant from various diseases. This dual function increases the survival rate of plants and ensures that they grow healthy and strong. You can find out more about this in our article about secondary plant substances.

Occurrence of flavonoids in food

Flavonoids are found in a variety of foods, including fruit and vegetables, tea, wine and chocolate.

  • Fruits and vegetables: Fruits such as apples, berries and citrus fruits are rich in flavonoids. Vegetables such as onions, kale and peppers also contain large amounts of them. These compounds contribute to the bright colors of these foods.
  • Tea: Both black and green tea are excellent sources of flavonoids. They contain a specific type of flavonoid - catechins. One of these is EGCG, which has a positive effect on NAD metabolism, among other things.
  • Wine: Red wine in particular is known for its high flavonoid content. The flavonoids in red wine come from the skin of the grapes and are believed to contribute to the positive effects of the drink on heart health. The best-known example is certainly resveratrol.
  • Schokolade: Dunkle Schokolade ist ein weiteres Lebensmittel, das reich an Flavonoiden ist. Die Flavonoide in dunkler Schokolade sind als Flavanole bekannt, die nachweislich den Blutfluss verbessern und den Blutdruck senken. Die süße Versuchung hat also tatsächlich auch gesundheitliche Vorteile, wenn auch nur mit sehr hohem Kakaoanteil (<70%).
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Benefits of flavonoids from human studies

There are a growing number of human studies that point to the health benefits of flavonoids.

Cardiovascular Health: Numerous studies have linked flavonoid consumption to improved cardiovascular health.

Brain health: Flavonoids may also support brain health. Some research suggests that flavonoids may improve cognitive function and help improve the course of neurodegenerative diseases such as Alzheimer's and Parkinson's.

Diabetes Treatment: Some studies also suggest that flavonoids may help regulate blood sugar levels, so they may be beneficial for diabetics or people with prediabetes (impaired insulin action).

Flavonoids bioavailability

Although they are abundant in our food, the bioavailability of flavonoids - i.e. how much of these compounds can be absorbed and utilized by the body - is relatively low. There are several reasons for this:

  • Metabolism: After ingestion, flavonoids undergo extensive metabolic processes in the body that can alter their structure and function. This process may limit the amount of bioactive flavonoids reaching the bloodstream and tissues.
  • Intestinal absorption: The absorption of flavonoids in the intestine can vary greatly depending on their structure. Some flavonoids are absorbed only with difficulty and are largely excreted with the feces.
  • Interaction with other nutrients: Flavonoids can interact with other nutrients in the diet, which can affect their absorption. For example, proteins and fats can bind to flavonoids and reduce their availability.

Despite these problems, there are ways to improve flavonoid bioavailability:

Consumption together with fats: Some studies suggest that consumption of flavonoids together with dietary fats may increase their absorption. This is because fats can improve the solubility of flavonoids, making them easier to absorb. The fat solubility of many secondary plant compounds is responsible for this.

Processing and cooking methods: Certain processing and cooking methods can increase the bioavailability of flavonoids. For example, chopping and mincing fruits and vegetables can release flavonoids from plant cells. Accordingly, the digestion effort is lower and more efficient. The result is increased absorption of flavonoids from food.

Dietary supplementation: flavonoid supplements often use formulations designed to improve bioavailability, such as encapsulation in liposomes or phospholipids. In the case of Quercetin as the most prominent flavonoid representative, bioavailability was increased twenty-fold by packaging with phospholipids and combining with vitamin C.

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Extraction of flavonoids for food supplements

The production of flavonoid dietary supplements can be challenging, as the extraction and drying processes quite often lead to impurities.

However, obtaining these compounds in pure and concentrated form for use in dietary supplements can be a complex process.

Conventional extraction methods use solvents that can introduce impurities and may not efficiently extract all available flavonoids. The drying process, which is often necessary to obtain a stable and storable product, can also compromise the quality and integrity of the flavonoids, leading to a potential loss of potency. Here it is very important to pay attention to high quality, purity and testing for heavy metal contamination when making the selection.

Risks of flavonoid overdose

While flavonoids offer many benefits, there are also risks associated with their overconsumption. These include the following:

Potential toxicity: Very high doses of several grams of certain flavonoids may have toxic effects. For example, some studies have shown that high amounts of quercetin can potentially damage the kidneys.

Drug interactions: Flavonoids may interact with certain drugs and interfere with their effectiveness. For example, they may interfere with the processing of certain drugs in the body, resulting in higher or lower drug levels in the body than expected.

Hormonal effects: Some flavonoids, particularly the isoflavones found in soy products, can mimic estrogen in the body. While this can be beneficial in some cases, it can also lead to hormonal imbalance if consumed in excessive amounts.

Our conclusion on flavonoids

Flavonoids are naturally occurring phytochemicals found in a variety of fruits, vegetables and other foods. They are known for their antioxidant properties and are associated with a lower risk of various chronic diseases.

Despite the many benefits of flavonoids, it is important to remember that excessive intake can lead to risks such as potential toxicity, drug interactions, and hormonal effects. Therefore, when consuming them in the form of dietary supplements, attention should be paid above all to transparent manufacturer's instructions, laboratory tests and compliance with consumption recommendations.


  • Ahmed, Maruf, and Jong-Bang Eun. "Flavonoids in fruits and vegetables after thermal and nonthermal processing: A review." Critical reviews in food science and nutrition vol. 58,18 (2018): 3159-3188. link
  • Toh, J Y et al. "Flavonoids from fruit and vegetables: a focus on cardiovascular risk factors." Current atherosclerosis reports vol. 15,12 (2013): 368. link
  • Magrone, Thea et al. "Cocoa and Dark Chocolate Polyphenols: From Biology to Clinical Applications." Frontiers in immunology vol. 8 677. 9 Jun. 2017, Link
  • Wang, Xia et al. "Flavonoid intake and risk of CVD: a systematic review and meta-analysis of prospective cohort studies." The British journal of nutrition vol. 111.1 (2014): 1-11. link
  • Macready, Anna L et al. "Flavonoids and cognitive function: a review of human randomized controlled trial studies and recommendations for future studies." Genes & nutrition vol. 4,4 (2009): 227-42. link
  • Zamora-Ros, Raul et al. "The association between dietary flavonoid and lignan intakes and incident type 2 diabetes in European populations: the EPIC-InterAct study." Diabetes care vol. 36,12 (2013): 3961-70. link