Luteolin – A Flavonoid for Immune Modulation
An overactive immune system can result in seasonal allergies and other concerns. However, bioflavonoids like luteolin are nutrients which may offer support for immune system balance.
An overactive immune system can result in seasonal allergies. However, there are a variety of nutrients which offer support for immune system balance. Plant flavonoids like quercetin, kaempferol, chrysin and luteolin among many others, are present in fruits and vegetables and well known for their antioxidant and immune balancing properties. Flavonoid molecules modulate immune activity through activation of anti-oxidative enzymes, suppression of the NFκB pathway and inhibiting the production of inflammatory substances.
Luteolin is a yellow, crystalline, polyphenolic flavonoid that is present in many vegetables and some fruits especially green peppers, chili peppers, celery, radicchio, red leaf lettuce, lemons and pumpkin. Luteolin is also present in olive oil as well as herbs and teas, including rosemary, thyme, oregano, peppermint, and chamomile. Although luteolin is widespread in fresh fruits and vegetables, the estimated daily consumption from a typical diet is less than 1 mg per day. (1) People who eat more processed foods and fewer fresh fruits, vegetables, and herbs consume even less.
Research shows that luteolin offers some unique benefits for healthy immune function. It supports mast cell stability; it attenuates airway mucus production by inhibiting gamma-aminobutyric acid A (GABAA) receptors; it supports healthy inflammation response by modulating immune cytokines; and it can cross the blood-brain barrier to support brain health.
The discovery of its unique molecular mechanisms of action have brought luteolin into the limelight for supporting immune balance. Studies of luteolin absorption and metabolism in humans show that plasma concentrations of luteolin and its conjugates reach the highest level approximately one hour after oral dosing.(2) Luteolin has a half-life of less than five hours, which means that for the greatest benefit, it’s necessary to take it multiple times a day to maintain appropriate levels in systemic circulation.
Cytokine modulation
High levels of inflammatory cytokines are present in allergic and autoimmune conditions. Luteolin has been shown to inhibit IgE-mediated production of interleukin-6 (IL-6) and tumor necrosis factor-alpha (TNF-a).(3) Luteolin also inhibits central mediators of inflammation, including cyclooxygenase-2 (COX-2) and nuclear factor-kappa B (NF-kB).(4) In an experimental model of autoimmune thyroiditis in mice, luteolin demonstrated an ability to inhibit interferon-gamma (IFN-l)-induced increases in COX-2, and also to inhibit TNF-a secretion.(5)
Mast Cell Stabilization
Mast cells play a role in immune response and wreak havoc in patients with allergies. When stimulated by immunoglobulin E (IgE) in reaction to even tiny amounts of allergens, mast cells degranulate, release histamine and cause symptoms like sneezing, congestion, wheezing, itchy eyes, hives, and brain fog.
However, luteolin supports mast cell stabilization.(6,7) Luteolin has been identified as the active ingredient in two herbs historically used for immune imbalance and seasonal concerns: Impatiens textori (impatiens) and Perilla frutescens (perilla). (8,9) Experimental studies in mice have shown that luteolin is responsible for the immune balance effects of perilla leaves.(5) In a study of 15 different plant flavonoids, luteolin demonstrated the greatest inhibitory effect of all flavonoids on mast-cell histamine release, even greater than quercetin (10)
Mucus attenuation
Excessive mucus production in the airways is a result of allergic inflammation. Studies have shown that activation of GABAA receptors plays a role in mucus oversecretion. An experimental study in 2016 demonstrated that luteolin attenuated mucus production from goblet cells by inhibiting GABAA receptors.(11) Also, luteolin showed a beneficial effect on airway responsiveness, decreasing bronchoconstriction in experimentally induced asthma in mice and cats.(12,13)
Crossing the blood-brain barrier:
Many neuropsychiatric and neurodegenerative disorders are thought to involve inflammation within the brain. Studies show that luteolin crosses the blood-brain barrier and stabilizes T-cell activation as well as mast cells within the brain.(14)