Myricetin is a naturally occurring compound found in plants, belonging to the flavonoid group. Flavonoids are polyphenols, plant pigments widely distributed in the plant kingdom, contributing to the healthful properties of many plant-based foods. Myricetin is a flavonol, a subclass of flavonoids, found in diverse dietary sources. It is structurally similar to other well-known flavonoids like fisetin, luteolin, and quercetin.
Food Sources of Myricetin
Myricetin is found in various everyday foods. Notable berry sources include cranberries, blueberries, and goji berries. Red and purple grapes also provide this compound.
Many vegetables contribute myricetin, including onions (especially red onions), and leafy greens like kale and chard. Fennel leaves and parsley are sources. Walnuts are a prominent nut source.
Green tea and red wine also contain myricetin. Black fruits can contain myricetin in quantities between 14 and 142 mg/kg. The concentration of myricetin in plant foods can vary due to factors like genetic makeup, environmental conditions, ripeness, and processing methods, which can reduce amounts significantly. Honey has also been found to contain myricetin, with quantities ranging from approximately 29.2 to 289.0 micrograms per 100 grams in some varieties.
Biological Activities of Myricetin
Myricetin functions in the body primarily through its antioxidant and anti-inflammatory properties. Oxidative stress occurs when there is an imbalance between the production of reactive oxygen species (ROS), often called free radicals, and the body’s ability to neutralize them. These unstable molecules can damage cellular components like lipids, DNA, and proteins. Myricetin, with its polyphenolic structure rich in hydroxyl groups, can neutralize these harmful molecules, thereby protecting cells from oxidative damage.
Myricetin can scavenge for ROS and chelate intracellular transition metal ions that contribute to ROS production. It can also enhance the effects of other antioxidants and induce the enzyme glutathione S-transferase (GST), which helps protect cells against oxidative stress. Studies have shown myricetin can restrict hydrogen peroxide-induced DNA strand breakage in human lymphocytes.
Myricetin also demonstrates anti-inflammatory effects. Inflammation is a natural body’s response to injury or infection. Myricetin may help modulate inflammatory pathways by inhibiting the production of cytokines, which are signaling molecules involved in inflammation.
Myricetin has been observed to interfere in inflammatory signal pathways by inhibiting various kinases and the function of tumor necrosis factor alpha (TNF-α), a pro-inflammatory cytokine. It can also suppress NF-κB, a protein complex that controls DNA transcription in response to inflammatory stress, by affecting mediators like Akt and mTOR. This modulation of inflammatory responses contributes to its overall biological profile.
Potential Health Applications
Research suggests myricetin may offer various health applications. Studies have explored its role in metabolic health, particularly concerning blood sugar regulation and insulin sensitivity. In mouse models of metabolic diseases, myricetin supplementation has been shown to reduce blood glucose and insulin levels. It also appears to improve lipid profiles by reducing triglycerides, total cholesterol, and low-density lipoprotein (LDL) cholesterol.
Myricetin has been observed to enhance insulin action and restore peripheral insulin sensitivity in studies involving mice with metabolic syndrome, which includes conditions like obesity and dyslipidemia. This involves improvements in the expression of insulin receptors and glucose transporter 4 (GLUT4), responsible for glucose uptake into cells. It may also protect pancreatic tissue and reduce markers of obesity.
Regarding cardiovascular support, myricetin’s properties may contribute to heart health. Its antioxidant capabilities can help protect blood vessels by preventing the oxidation of LDL, a process implicated in atherosclerosis. Myricetin has also been studied for its anti-hypertensive and anti-atherosclerotic effects in both in vitro and in vivo models. It may also inhibit platelet aggregation, a process involved in blood clot formation.
Emerging research also points to myricetin’s neuroprotective potential, focusing on its ability to protect brain cells from damage. It has demonstrated effects against oxidative stress in neuronal injury models by decreasing reactive oxygen species formation and enhancing antioxidant enzyme activity. Myricetin may also help protect against neuroinflammation and cellular apoptosis in the nervous system. Studies are investigating its relevance in conditions like cerebral ischemia, Alzheimer’s disease, and Parkinson’s disease, where it has shown ability to mitigate neuronal damage and improve neurological function.
Intake and Safety Considerations
When considering myricetin intake, a food-first approach is generally recommended over isolated supplements. Myricetin from whole food sources is considered safe and is part of a broader dietary pattern that provides numerous beneficial compounds. The body’s absorption of myricetin, known as bioavailability, can be influenced by factors such as its solubility and whether it is consumed with meals containing healthy fats. Oral bioavailability of myricetin has been reported to be relatively low in some studies, around 9.62% to 9.74% at certain doses.
There is currently no established Recommended Daily Allowance (RDA) for myricetin. While myricetin from food sources is well-tolerated, high-dose supplements may present potential side effects. These can include mild digestive discomfort such as nausea or diarrhea, particularly when taken on an empty stomach. Allergic reactions, though rare, are also possible, especially for individuals sensitive to plant flavonoids.
High concentrations of myricetin from supplements may interact with certain medications. Studies indicate it may affect drugs metabolized by the liver, including anticoagulants and anti-inflammatory medications, by modulating enzyme activity. Given these considerations, consulting a healthcare professional is advised before starting any new myricetin supplement, especially for those with pre-existing health conditions or who are taking other medications.