Does oolong tea have quercetin? The full flavonoid breakdown

January 10, 2026 •

4 min read

As a semi-oxidized tea, oolong tea contains a range of powerful antioxidants, and yes, this includes the flavonoid quercetin. The unique partial oxidation process gives oolong tea a distinct flavonoid profile that offers numerous potential health benefits.

Quick Summary

Oolong tea contains quercetin, alongside other flavonoids, with levels and types varying based on its unique partial oxidation process, which gives it a distinct antioxidant profile.

Key Points

Yes, Oolong Contains Quercetin: Oolong tea does contain quercetin, a powerful antioxidant and anti-inflammatory flavonoid.
Semi-Oxidized Profile: The partial oxidation process of oolong tea gives it a flavonoid profile that is a blend of compounds found in both green and black teas.
More than Just Quercetin: Besides quercetin, oolong tea is also rich in other beneficial compounds, including catechins, theaflavins, thearubigins, and the amino acid L-theanine.
Health Benefits: The flavonoids in oolong tea contribute to heart health, metabolism and weight management, bone density, and improved brain function.
Processing Matters: The specific amount of quercetin and other flavonoids can differ based on the tea's cultivar, oxidation level, and processing methods.
Brewing Impacts Flavor and Content: Using the correct water temperature and steeping time is essential for extracting the maximum amount of beneficial compounds while maintaining optimal flavor.

Oolong Tea: A Semi-Oxidized Powerhouse of Flavonoids

Oolong tea, a traditional Chinese tea, comes from the same Camellia sinensis plant as green and black teas. The key difference lies in its unique processing, which involves partial oxidation. This process determines the tea's color, flavor, and, importantly, its flavonoid content. Unlike green tea, which is unoxidized, or black tea, which is fully oxidized, oolong's partial oxidation places it in a category of its own. This means it contains a blend of bioactive compounds found in both green and black teas, giving it a unique set of health properties.

The Role of Processing in Quercetin Content

Processing plays a pivotal role in shaping the final flavonoid composition of any tea. For oolong, the semi-oxidized process creates a delicate balance. A 2017 review on oolong tea notes that during processing, catechins can be further transformed into other compounds like theaflavins. However, research also confirms the unique occurrence of quercetin and other flavonols like kaempferol and myricetin in oolong tea. The precise level can vary significantly depending on the specific cultivar of the tea plant, the terroir, and the duration and method of oxidation used by the tea master. In general, though, studies have shown that oolong tea exhibits mid-level antioxidant activity, sitting somewhere between the high activity of green tea and the processed black tea.

Quercetin and Other Antioxidants in Oolong Tea

Yes, oolong tea unequivocally contains quercetin, a potent flavonoid known for its powerful antioxidant and anti-inflammatory properties. However, it is not the only beneficial compound. Oolong tea is rich in polyphenols and other flavonoids, including:

Catechins: Monomeric flavan-3-ols, such as EGCG (epigallocatechin gallate), which are abundant in green tea but also present in oolong.
Theaflavins and Thearubigins: These are complex flavonoid polymers formed during the oxidation process, more prevalent in black tea but also found in oolong due to its partial oxidation.
L-theanine: An amino acid that promotes relaxation and alertness, balancing the effects of caffeine.

A Comparison of Flavonoids in Brewed Teas


Flavonoid Category	Green Tea (Unoxidized)	Oolong Tea (Partially Oxidized)	Black Tea (Fully Oxidized)
Catechins (EGCG, EGC, etc.)	High concentration, especially EGCG.	Lower than green tea due to partial oxidation.	Lowest concentration due to extensive oxidation.
Theaflavins & Thearubigins	Very low to negligible amounts.	Moderate amounts due to semi-oxidation.	High concentration, giving the dark color.
Flavonols (Quercetin, Kaempferol, Myricetin)	Present in significant amounts.	Present, confirmed by studies.	Present, similar levels to green tea.
Overall Antioxidant Activity	High due to high catechin content.	Mid-level, between green and black tea.	Can be high, depending on preparation.

Health Benefits Associated with Oolong's Flavonoids

The flavonoids and polyphenols found in oolong tea, including quercetin, contribute to numerous health benefits. Research indicates that regular consumption may provide the following advantages:

Metabolism and Weight Management: The combination of caffeine and polyphenols in oolong tea has been shown to boost metabolism and increase fat oxidation. This can help increase the number of calories burned daily and aid in weight loss.
Heart Health: Antioxidants like quercetin can help reduce the risk of cardiovascular diseases by lowering bad (LDL) cholesterol and improving overall circulation. Studies on oolong tea drinkers have shown a reduced risk of heart disease.
Anti-inflammatory Effects: Quercetin is a powerful anti-inflammatory agent. Oolong tea's ability to combat oxidative stress and inflammation helps protect cells from damage caused by free radicals.
Bone and Dental Health: The antioxidants in oolong tea can help increase bone mineral density, reducing the risk of osteoporosis. It also helps maintain good dental health by reducing plaque and inhibiting harmful bacteria.
Brain Function: The caffeine and L-theanine in oolong tea work together to enhance cognitive function, improve memory, and reduce stress. The antioxidant properties also offer neuroprotective benefits, potentially helping prevent age-related cognitive decline.

Practical Brewing for Maximum Benefits

To get the most out of your oolong tea and its flavonoid content, proper brewing is key. Over-steeping can draw out bitter flavors, while under-steeping may not release the full spectrum of compounds. Here is a simple guide to follow:

Select a High-Quality Tea: Choose loose-leaf oolong from a reputable source for the best flavor and concentration of beneficial compounds.
Use the Correct Water Temperature: Boil water and let it cool for a minute or two before pouring. Ideal temperature is between 190°F to 200°F (88°C to 93°C).
Use the Right Ratio: A good starting point is about 1 teaspoon of oolong leaves for every 8 ounces of water.
Observe Steeping Time: Steep for 1 to 5 minutes, adjusting to taste. Lighter oolongs may need less time, while darker, more oxidized oolongs can handle a longer steep.
Re-steep the Leaves: Many high-quality oolong teas can be re-steeped multiple times, revealing new flavor notes with each infusion. This also allows you to extract more of the remaining beneficial compounds.

Conclusion

In summary, oolong tea is a reliable source of quercetin and a rich assortment of other flavonoids, offering a compelling array of health benefits. Its unique semi-oxidized state places it in an interesting middle ground, combining the benefits of both green and black teas into one flavorful brew. While the exact quantity of quercetin can vary depending on the specific tea's processing and origin, its presence contributes to oolong's potent antioxidant, anti-inflammatory, and overall health-promoting properties. Whether you are seeking improved heart health, enhanced metabolism, or simply a delicious and complex beverage, incorporating oolong tea into your daily routine is a choice grounded in both traditional wisdom and scientific evidence.

For additional information on flavonoids in tea and their health implications, research into studies on tea composition is recommended. See for example, research compiled by the Linus Pauling Institute at Oregon State University.

Linus Pauling Institute | Oregon State University

Frequently Asked Questions

Quercetin is a type of plant pigment, or flavonoid, found in many fruits, vegetables, and teas. It is well-regarded for its potent antioxidant and anti-inflammatory effects.

While both teas contain quercetin, green tea generally has a higher concentration of total catechins due to its lack of oxidation. Oolong's partial oxidation means some catechins are converted, but its overall antioxidant activity is a unique balance between green and black tea.

Oolong tea's semi-oxidation process causes some of its catechins to polymerize into complex compounds like theaflavins and thearubigins. This creates a different flavonoid profile compared to unoxidized green tea, but still retains a significant level of antioxidants, including quercetin.

Research suggests that the combination of caffeine and polyphenols in oolong tea can aid in weight loss by boosting metabolism and increasing fat oxidation. However, it should be part of a healthy diet and exercise routine to be most effective.

Like other teas, oolong tea contains catechins that can interfere with iron absorption, particularly in individuals with existing iron deficiencies. Moderation is advised, and those concerned can drink tea outside of mealtimes.

Oolong tea contains caffeine, and excessive consumption can lead to side effects like anxiety, headaches, and insomnia. Most adults can safely consume up to 400 mg of caffeine daily, which is equivalent to 6–10 cups of oolong tea.

Yes, quercetin and other antioxidants in oolong tea support heart health by helping to reduce bad cholesterol levels and lower blood pressure. Consistent consumption is linked to a lower risk of cardiovascular disease.