Higher plasma quercetin levels following oral administration of an onion skin extract compared with pure quercetin dihydrate in humans.
OBJECTIVE
To investigate the plasma kinetics of quercetin derived from hard capsules filled with onion skin extract powder or quercetin dihydrate in humans.


METHODS
In a randomized, single-blind, diet-controlled crossover study, 12 healthy subjects (six men and six women) aged 21-33 years were administered a single oral supra-nutritional dose of approximately 163 mg quercetin derived from onion skin extract powder (containing 95.3 % of total flavonoids as quercetin aglycone) or quercetin dihydrate (134 mg quercetin aglycone equivalent). Blood samples were collected before and during a 24-h period after quercetin administration. The concentrations of quercetin and its two monomethylated derivatives, isorhamnetin (3'-O-methyl quercetin), and tamarixetin (4'-O-methyl quercetin), were measured using HPLC with fluorescence detection after plasma enzymatic treatment.


RESULTS
The systemic availability, determined by comparing the plasma concentration-time curves of quercetin, was 4.8 times higher, and the maximum plasma concentration (Cmax) was 5.4 times higher after ingestion of the onion skin extract than after ingestion of pure quercetin dihydrate. By contrast, tmaxdid not differ significantly between the two formulations. The Cmaxvalues for isorhamnetin and tamarixetin were 3.8 and 4.4 times higher, respectively, after administration of onion skin extract than after pure quercetin dihydrate. The plasma kinetics of quercetin were not significantly different in men and women.


CONCLUSIONS
Quercetin aglycone derived from onion skin extract powder is significantly more bioavailable than that from quercetin dihydrate powder filled hard capsules.
Department of Nutrition and Food Sciences, Nutritional Physiology, University of Bonn, Endenicher Allee 11-13, 53115, Bonn, Germany.
Constanze
C
Burak
Department of Nutrition and Food Sciences, Nutritional Physiology, University of Bonn, Endenicher Allee 11-13, 53115, Bonn, Germany.
Verena
V
Brüll
Department of Biopharmaceutics and Pharmaceutical Technology, Institute of Pharmacy and Biochemistry, Johannes Gutenberg University, Mainz, Germany.
Peter
P
Langguth
Institut Prof. Dr. Georg Kurz GmbH, Cologne, Germany.|Department of Nutrition and Food Sciences, Food Technology and Food Biotechnology, University of Bonn, Bonn, Germany.
Benno F
BF
Zimmermann
Institute of Clinical Chemistry and Clinical Pharmacology, University Hospital Bonn, Bonn, Germany.
Birgit
B
Stoffel-Wagner
Department of Anaesthesiology and Intensive Care Medicine, University Hospital Bonn, Bonn, Germany.
Udo
U
Sausen
Department of Nutrition and Food Sciences, Nutritional Physiology, University of Bonn, Endenicher Allee 11-13, 53115, Bonn, Germany.
Peter
P
Stehle
Institute of Animal Nutrition and Physiology, Christian-Albrechts-University Kiel, Kiel, Germany.
Siegfried
S
Wolffram
Department of Nutrition and Food Sciences, Nutritional Physiology, University of Bonn, Endenicher Allee 11-13, 53115, Bonn, Germany. s.egert@uni-bonn.de.
Sarah
S
Egert
D000284:Administration, Oral; D000328:Adult; D001682:Biological Availability; D018592:Cross-Over Studies; D004187:Disaccharides / Q000008:administration & dosage / Q000097:blood / Q000493:pharmacokinetics; D004305:Dose-Response Relationship, Drug; D005260:Female; D006801:Humans; D008297:Male; D019697:Onions / Q000737:chemistry*; D010936:Plant Extracts / Q000008:administration & dosage* / Q000097:blood* / Q000493:pharmacokinetics; D011208:Powders; D011794:Quercetin / Q000008:administration & dosage* / Q000031:analogs & derivatives / Q000097:blood* / Q000493:pharmacokinetics; D016037:Single-Blind Method; D055815:Young Adult
D004187:Disaccharides; D010936:Plant Extracts; D011208:Powders; C047368:3-methylquercetin; C508967:tamarixetin; D011794:Quercetin
Bioavailability; Human study; Onion; Quercetin