What are the ingredients in bioflavonoids? A comprehensive guide

January 5, 2026 •

5 min read

While the term 'bioflavonoids' is often used interchangeably with 'flavonoids,' they are not a single ingredient but a vast family of thousands of naturally occurring plant compounds. Found abundantly in fruits, vegetables, and herbs, these compounds offer potent antioxidant properties and work synergistically with Vitamin C. To understand their health effects, it is crucial to know what are the ingredients in bioflavonoids and their diverse roles.

Quick Summary

Bioflavonoids are a vast group of plant-based polyphenolic compounds, not a single ingredient, found in fruits, vegetables, and herbs. Key examples include hesperidin, quercetin, and rutin, prized for their antioxidant and anti-inflammatory properties, often working alongside Vitamin C for enhanced effects.

Key Points

Diverse Compounds: Bioflavonoids are not a single ingredient but a broad class of polyphenolic compounds found in plants.
Key Subclasses: Important subclasses include flavonols (quercetin, rutin), flavanones (hesperidin, naringenin), flavan-3-ols (catechins), and anthocyanidins (cyanidin).
Rich Food Sources: Excellent dietary sources are colorful fruits (especially citrus and berries), vegetables (onions, kale), teas, and cocoa products.
Antioxidant Power: Bioflavonoids are potent antioxidants and anti-inflammatory agents that help protect the body from free radical damage.
Synergy with Vitamin C: They work synergistically with Vitamin C, enhancing its absorption and antioxidant activity in the body.
Supplement Forms: Often sold as complexes, particularly citrus bioflavonoid complexes, but content can vary significantly between brands.
Potential Interactions: High doses from supplements can interact with certain medications, including blood thinners and some blood pressure drugs.

The Diverse World of Bioflavonoid Ingredients

Bioflavonoids are a fascinating and diverse family of plant-based compounds, each with a unique chemical structure and specific functions. Their molecular architecture is based on a 15-carbon skeleton, which varies slightly to form different subclasses. This diversity is precisely why there is no single answer to the question "what are the ingredients in bioflavonoids?" but rather a spectrum of beneficial compounds found in various foods.

Flavonols: Found in Onions and Apples

Flavonols are a major subclass of flavonoids widely distributed in the plant kingdom. Some of the most well-known flavonol ingredients include:

Quercetin: Abundant in onions, apples, and berries, quercetin is known for its antioxidant and anti-inflammatory effects. It has been studied for its potential to stabilize mast cells, which release histamine during allergic reactions.
Rutin: Found in buckwheat, asparagus, and citrus fruits, rutin is a glycoside of quercetin. It has been associated with strengthening blood vessel walls and improving microcirculation.
Kaempferol and Myricetin: These are other common flavonols present in foods like kale, broccoli, and teas.

Flavanones: The Citrus Connection

This subclass is predominantly found in citrus fruits and is responsible for their distinct bitter flavors. Key flavanone ingredients include:

Hesperidin: The most abundant flavonoid in oranges and lemons, hesperidin is concentrated in the white pith and peel. It is often used in supplements to support vascular health and improve circulation.
Naringenin and Naringin: These flavanones are most famously found in grapefruit, giving it its bitter taste.
Eriodictyol: Found in lemons and other citrus fruits, it is also a powerful antioxidant.

Flavan-3-ols (Catechins): Power in Tea and Cocoa

Catechins are a subgroup of flavonoids found in a wide variety of foods, with some of the most prominent sources being tea and cocoa products. Notable ingredients include:

Epicatechin (and Epigallocatechin Gallate or EGCG): These are the main catechins in green tea and are extensively studied for their health benefits, including their strong antioxidant properties.
Proanthocyanidins: These are polymers of flavan-3-ols and are abundant in cocoa, grape seeds, and cinnamon.

Anthocyanidins: The Color of Berries and Grapes

Anthocyanidins are the pigments responsible for the vibrant red, purple, and blue colors in many fruits and vegetables. The glycosylated form is known as anthocyanins. Examples of these ingredients include:

Cyanidin, Delphinidin, and Malvidin: These are key anthocyanidins found in berries (like blueberries, cranberries, and raspberries) and red wine.

Flavones and Isoflavones: From Parsley to Soy

Flavones (Apigenin and Luteolin): Found in herbs like parsley and celery, as well as chamomile and peppermint. They have anti-inflammatory properties.
Isoflavones (Genistein and Daidzein): Primarily found in soy and other legumes, these are known for their phytoestrogenic activity and potential impact on hormone balance.

Synergy with Vitamin C

Bioflavonoids have a well-documented synergistic relationship with Vitamin C, enhancing its absorption and extending its antioxidant activity in the body. Because of this, many bioflavonoid supplements are sold as a 'complex' combined with Vitamin C. This co-existence in nature, notably in citrus fruits, underscores their combined benefits for immune support, tissue repair, and vascular health.

Natural Sources vs. Bioflavonoid Supplements

For most people, a diet rich in fruits and vegetables will provide a sufficient intake of bioflavonoids. However, some individuals may opt for supplements, which often contain concentrated extracts. The table below compares the ingredients and characteristics of obtaining bioflavonoids from whole foods versus supplements.


Feature	Natural Food Sources	Bioflavonoid Supplements
Ingredient Profile	Rich in a wide spectrum of flavonoids and co-factors. The mix depends on the specific foods consumed.	Typically contain a concentrated extract from specific sources, such as citrus. May contain isolated compounds like quercetin or hesperidin.
Example Ingredients	Quercetin (onions, apples), Hesperidin (oranges), Anthocyanins (berries).	Often standardized to specific flavonoids like hesperidin (90%) and diosmin (10%) or contain a mix of citrus flavonoids.
Absorption	Generally absorbed more slowly but steadily, with complex interactions with other nutrients and gut microbiota.	Bioavailability can be low unless a specialized delivery method, such as micronization or liposomal encapsulation, is used.
Dosage	Varies widely based on diet. The USDA provides databases for flavonoid content.	Standardized doses, often ranging from 500mg to 1000mg or more per serving.
Considerations	The best way to get a wide variety of bioflavonoids. Offers the complete 'package' of plant nutrients.	Useful for targeted support or therapeutic purposes, but requires careful consideration due to potential drug interactions.

Important Considerations and Interactions

While bioflavonoids are generally considered safe, especially through dietary intake, it's important to be aware of certain considerations, particularly with concentrated supplements:

Medication Interactions: Some bioflavonoids can interact with medications. For example, certain citrus bioflavonoids found in grapefruit (naringin) can affect enzymes that metabolize drugs like calcium channel blockers, potentially increasing blood levels of the medication. The citrus bioflavonoid tangeretin can reduce the effectiveness of tamoxifen, a breast cancer drug. Concentrated flavonoids can also interact with blood thinners like warfarin.
Pregnancy and High Doses: Preliminary studies have suggested a potential link between very high doses of certain bioflavonoid supplements during pregnancy and an increased risk of infant leukemia, though the evidence is not conclusive. Pregnant women are generally advised against taking megadoses of bioflavonoids.
Side Effects: At high doses, some individuals may experience mild side effects like nausea, diarrhea, headaches, or blurred vision. Allergic reactions, while rare, can also occur.
Unspecified Complexes: As noted in a study by Ankit Gupta et al., the actual flavonoid content in commercial supplements can vary significantly, even when labeled as a "complex". Consumers should research the specific ingredients and standardization of any supplement they consider.

Conclusion: Embracing the Bioflavonoid Ingredients

To answer the question "what are the ingredients in bioflavonoids?" requires understanding that they are not one substance, but a diverse and complex group of plant-derived nutrients. From the quercetin in your onions to the hesperidin in your oranges and the anthocyanins in your berries, a wide array of specific flavonoid compounds contribute to the overall health benefits associated with these polyphenols. These ingredients function primarily as powerful antioxidants and anti-inflammatory agents, often enhancing the effects of Vitamin C. For most people, a colorful, varied diet is the best way to get a broad spectrum of bioflavonoids. However, for those considering supplements for targeted support, understanding the specific types of flavonoids and potential interactions is key to making an informed choice. For more detailed information on flavonoids and their properties, consider consulting authoritative sources like the Linus Pauling Institute.

Frequently Asked Questions

Bioflavonoids, also known simply as flavonoids, are a large group of phytonutrients or plant chemicals. They are secondary plant metabolites with a distinct chemical structure and are responsible for the vibrant colors in many fruits, vegetables, and flowers.

No, bioflavonoids are not vitamins. Although they were once mistakenly called 'vitamin P' by researchers who noted their effect on capillary permeability, they are not essential for life in the same way true vitamins are and therefore are no longer classified as such.

Many plant-based foods are excellent sources. Key examples include citrus fruits, berries, apples, onions, kale, tea (especially green and black), and cocoa products. The specific types of flavonoids vary depending on the food.

Bioflavonoids and vitamin C have a synergistic relationship, meaning they enhance each other's effects. Flavonoids help stabilize vitamin C, support its absorption, and prolong its activity in the body. They are often found together in nature, and this pairing boosts their combined antioxidant power.

Citrus bioflavonoids are a specific subgroup of flavonoids found in citrus fruits like oranges, lemons, and grapefruits. They include hesperidin and naringenin and are concentrated in the fruit's pith and peel.

Yes, there are several different types or subclasses of bioflavonoids, including flavanols (e.g., quercetin), flavanones (e.g., hesperidin), flavan-3-ols or catechins (e.g., EGCG), and anthocyanidins (e.g., cyanidin).

For most individuals, a healthy and varied diet rich in colorful fruits and vegetables is sufficient for obtaining a wide spectrum of bioflavonoids. Supplements can provide a concentrated dose for specific health goals, but they are not necessary for everyone and may carry risks.

The effectiveness of bioflavonoid supplements depends on the specific compound, dosage, and quality of the supplement. Research shows benefits for certain conditions like vascular health, but absorption can be a challenge. It is best to consult a healthcare professional before starting supplementation.