Revolutionary Study Uncovers Pirin Protein’s Role in Quercetin Metabolism, Redefining Cellular Signaling Pathways
August 11, 2025 – A landmark study published in Molecular Pharmacology has overturned decades of scientific consensus by revealing that the protein Pirin does not regulate the NF-κB signaling pathway as previously believed. Instead, researchers discovered that Pirin functions as a quercetinase—an enzyme that metabolizes the flavonoid quercetin—a finding that could reshape our understanding of inflammation, cancer, and metabolic regulation.
The Unexpected Discovery
For years, Pirin was thought to be a co-activator of the NF-κB pathway, a critical regulator of immune responses and inflammation. However, a research team led by Dr. Meschkewitz at Michigan State University found no evidence of Pirin binding to p65 (a key NF-κB subunit), despite multiple attempts using surface plasmon resonance (SPR), size-exclusion chromatography (SEC), and fluorescence polarization (FP) assays.
Instead, the study revealed that Pirin is primarily localized in the endoplasmic reticulum (ER), where it degrades quercetin—a potent antioxidant found in foods like apples, onions, and berries. The team identified CCG-257081, a small-molecule inhibitor that competitively blocks Pirin’s quercetinase activity, leading to a significant increase in intracellular quercetin levels.
Implications for Health and Disease
Quercetin has long been studied for its anti-inflammatory, antioxidant, and potential anticancer properties. This discovery suggests that Pirin may play a crucial role in modulating quercetin’s bioavailability in cells, which could influence conditions like chronic inflammation, neurodegeneration, and even cancer progression.
“This finding forces us to reconsider how quercetin is regulated in the body,” said Dr. Lisabeth, a co-author of the study. “If Pirin controls quercetin degradation, then inhibiting Pirin could enhance quercetin’s therapeutic effects—something we’re now exploring in preclinical models.”
Who should avoid quercetin?
Very high doses of quercetin may damage the kidneys. You should take periodic breaks from taking quercetin. Pregnant women, breastfeeding women, and people with kidney disease should avoid quercetin. At doses greater than 1 g per day, there have been reports of damage to the kidneys.
Can I take quercetin and vitamin D together?
Yes, quercetin and vitamin D can generally be taken together. In fact, some studies suggest they may even work synergistically to support immune health. Quercetin, a flavonoid found in many fruits and vegetables, and vitamin D, a nutrient that supports immune function and cellular health, can be found in combination supplements.
What to avoid when taking quercetin?
Be careful if you are taking drugs such as antibiotics, cyclosporine, warfarin, or drugs that are changed by the liver. Quercetin may change how these drugs work and raise the risk of side effects. There don’t appear to be interactions between quercetin and foods or other herbs and supplements.
Is quercetin safe for children?
While quercetin is found naturally in many foods and is generally considered safe for adults in moderate amounts, there’s limited research on its safety and effectiveness for children, and caution is advised.
When to take quercetin？
You can take quercetin at any time of day. However, you should consider taking it at mealtimes because foods containing vitamin C, bromelain, and healthy fats can aid its absorption. Additionally, “some individuals may prefer to take it with meals to minimize potential gastrointestinal discomfort,” says Dr. Ormond.