Quercetin is a very common flavonoid found in many plants, fruits and vegetables.
It is present in large quantities in capers, onions, apples, berries, but also in green tea (Camellia sinensis) in red wine, and even in Ginkgo biloba, St. John’s Wart, Cranberry and especially in the Japanese pagoda tree.
It traps free radicals, chelates metals, activates the synthesis of glutathione and SOD (super oxide dismutase).
It protects renal tubular cells from lipoperoxidation (PIETRUCK & al, 2003).
In broiler chickens, quercetin supplementation stimulates the activity of antioxidant enzymes (SOD, catalase and glutathion peroxidase), reduces total cholesterol, LDL and reduces ALT (alanine aminotransferase). The weight of supplemented animals is 10% higher, as is the protein ratio (FARDOS & al, 2018).
Quercetin reduces neutrophils and cytokine production by inhibition of NF kappa B (COMALADA & al, 2005 ; MORIKAWA & al, 2003).
Quercetin is used in acute and chronic allergy treatments; like hay fever and chronic rhinitis. Its anti-inflammatory activity is explained by its ability to stabilize mast cells, neutrophilia, basophilia and by inhibiting histamine release (BLACKBURN & al, 1987 ; OGASAWAR & al, 1996).
Quercetin protects against allergies by inhibiting the production of immunoglobulin E (FARIDEH & al, 2010).
NISHTHA & al, in 2019, demonstrated in vitro that quercetin acts synergistically with curcumin on several melanoma cancer cell lines. They act together, inhibiting the bcl-2 gene and induce apoptosis by activation of caspases 3 and 7.
Like Green Tea EGCGs, quercetin inhibits telomerase activity, which is excessive in tumour processes, and restores apoptosis (FAZLULLAH & al, 2016).
In vitro, quercetin inhibits sphingomyelinase and has an anti-acute myeloid leukaemia activity (COLIN & al, 2018).
Quercetin sensitizes tumour cells during acute myeloid leukaemia to treatment with TRAIL (TNF-related apoptosis-induced ligand) and improves its effectivenes (ADELINE & al, 2018 ; RUSSO & al, 2007).
Quercetin induces apoptosis and is anti-proliferative against breast cancer (JAE-HOON & al, 2009).
These effects are in part due to its vasorelaxant, anti-inflammatory and antioxidant capabilities (RHOGHANI & al, 2004).
It inhibits platelet aggregation and thrombus formation (HUBBARD & al, 2004).
The improvement of the endothelial function is likely through an improvement of the e NOS (NO endothelial synthase). This results in vasodilatation, decreases the signs of hypertension and thus preserves the heart, vessels and kidneys from morphological and functional alterations (PEREZ-VIZCAINO, 2009).
It improves the function of the left ventricle. It reduces systolic and diastolic pressure, improves glomerular filtration rates in patients with gout and essential hypertension who have received a quercetin supplement for one year (KONDRATIUK & SYNYTSIA, 2018).
Quercetin everywhere and for everyone!
