Quercetin & luteolin: flavonoids, bioavailability and mast cell research
N. Thornton, MSc. · Molecular Biologist · 8 min · RARE Labs
Editorially updated:
Quercetin and luteolin are among the most studied flavonoids in mast cell research. What cell studies show, why intestinal absorption is the real hurdle — and what phytosomes change about it.
Quercetin and luteolin are flavonoids — plant compounds found in capers, onions, apples, parsley, celery and artichokes. Chemically they differ by a single hydroxyl group: quercetin is a flavonol, luteolin a flavone. Rutin is the sugar-bound glycoside of quercetin.
Both compounds have been studied in cultured human mast cells for more than two decades. Kimata et al. (2000) reported that luteolin and quercetin reduced IgE-mediated release of histamine, leukotrienes and prostaglandin D2 from human mast cells in vitro in a concentration-dependent manner. Weng et al. (2012) compared quercetin with the mast cell stabiliser cromolyn in cell experiments and reported stronger inhibition of cytokine release.
These findings are mechanistically interesting but come largely from cell cultures using concentrations rarely reached in human blood after normal intake. That is the core of the debate: not what a flavonoid does in a dish, but how much of it actually reaches the body.
Quercetin's bioavailability is considered low. It is poorly water-soluble, rapidly converted to glucuronides and sulphates in the gut and liver, and only a small fraction is absorbed unchanged. Studies in ileostomy volunteers (Hollman et al., 1995) also showed that form matters: glycosides from onions were absorbed better than pure quercetin aglycone.
One approach in formulation research is phytosomes — complexes of the plant compound with phospholipids from lecithin that improve solubility at the intestinal lining. In a pharmacokinetic study in healthy volunteers (Riva et al., 2019), a quercetin phytosome produced markedly higher plasma levels than unformulated quercetin — up to roughly 20-fold in that study.
The literature also discusses combining several flavonoids, since quercetin, luteolin and rutin differ in structure, solubility and metabolic pathway. Robust clinical trials on such combinations are still lacking; this is a reasoned research hypothesis, not an established effect.
Study design at a glance
- Type
- Evidence overview (in vitro + pharmacokinetics)
- Participants
- cell models, healthy volunteers
- Duration
- 1995–2019
What this means — and what it does not
- Mast cell data on quercetin and luteolin come mostly from cell models — they describe mechanisms, not effects in humans.
- For flavonoids, intestinal absorption is the decisive factor; raw-material form and formulation substantially affect plasma levels.
- Phytosomes are a pharmacokinetically studied way to increase quercetin bioavailability.
- No health claims are authorised for flavonoids in the EU; they replace neither diagnostics nor therapy.
Limitations
- In-vitro concentrations do not translate directly to humans.
- Pharmacokinetic studies measure plasma levels, not clinical endpoints; samples are small and partly manufacturer-funded.
- Human absorption data for luteolin are far scarcer than for quercetin.
- This article provides scientific information and makes no claim about the effect of any RARE product.
Sources
- Kimata M et al., Clin Exp Allergy 2000 — Effects of luteolin, quercetin and baicalein on immunoglobulin E-mediated mediator release from human cultured mast cellsKimata M, Shichijo M, Miura T et al. · Clin Exp Allergy · 2000 · PMID: 10718847
- Weng Z et al., PLoS One 2012 — Quercetin is more effective than cromolyn in blocking human mast cell cytokine release and inhibits contact dermatitis and photosensitivity in humansWeng Z, Zhang B, Asadi S et al. · PLoS One · 2012 · PMID: 22470478
- Hollman PC et al., Am J Clin Nutr 1995 — Absorption of dietary quercetin glycosides and quercetin in healthy ileostomy volunteersHollman PC, de Vries JH, van Leeuwen SD et al. · Am J Clin Nutr · 1995 · PMID: 7491892
- Riva A et al., Eur J Drug Metab Pharmacokinet 2019 — Improved Oral Absorption of Quercetin from Quercetin Phytosome®, a New Delivery System Based on Food Grade LecithinRiva A, Ronchi M, Petrangolini G et al. · Eur J Drug Metab Pharmacokinet · 2019 · PMID: 30328058
- Mlcek J et al., Molecules 2016 — Quercetin and Its Anti-Allergic Immune ResponseMlcek J, Jurikova T, Skrovankova S et al. · Molecules · 2016 · PMID: 27187333
- Theoharides TC et al., Front Neurosci 2015 — Brain "fog," inflammation and obesity: key aspects of neuropsychiatric disorders improved by luteolinTheoharides TC, Stewart JM, Hatziagelaki E et al. · Front Neurosci · 2015 · PMID: 26190965
Editorial note: these articles are contextual knowledge pieces and do not replace medical advice.
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