Quercetin and isorhamnetin aglycones are the main metabolites of dietary quercetin in cerebrospinal fluid.
METHODS
Reports on the protective effect of certain foods on brain functions are numerous; however, the permeability of the brain barriers by food components is still hardly recognised. There have been in vitro studies aimed at demonstrating this possibility, but not much is known about this phenomenon in in vivo systems. The objective of the study was to determine the metabolites of dietary quercetin (Q) in urine, blood plasma and cerebrospinal fluid (CSF) after intra-rumen administration of Q rich onion dry skin in an animal model.


RESULTS
Eleven sheep had permanently implanted cannulas in the third ventricle of the brain as the means for CSF collection. The animals were administered Q at the dose of 10 mg/kg bwt. For 12 h the concentration of Q metabolites was measured in urine, blood plasma, and CSF. It was demonstrated that while in blood plasma Q and isorhamnetin mono-glucuronides or mono-sulphates were the main metabolites (80%), in CSF their aglycones were the dominating ones (88%).


CONCLUSIONS
Q and IR aglycones are the main Q metabolites present in CSF after dietary Q intake. Their passive transport through blood-CSF barrier or a de-conjugating mechanism within that barrier may be involved.
Department of Chemistry and Biodynamics of Food, Institute of Animal Reproduction and Food Research, Polish Academy of Sciences, Olsztyn, Poland.
Wiesław
W
Wiczkowski
Department of Local Physiological Regulations, Institute of Animal Reproduction and Food Research, Polish Academy of Sciences, Olsztyn, Poland.
Janina
J
Skipor
Department of Endocrinology, Kielanowski Institute of Animal Physiology and Nutrition, Polish Academy of Sciences, Jablonna, Poland.
Tomasz
T
Misztal
Department of Chemistry and Biodynamics of Food, Institute of Animal Reproduction and Food Research, Polish Academy of Sciences, Olsztyn, Poland.
Dorota
D
Szawara-Nowak
Department of Chemistry and Biodynamics of Food, Institute of Animal Reproduction and Food Research, Polish Academy of Sciences, Olsztyn, Poland.
Joanna
J
Topolska
Department of Chemistry and Biodynamics of Food, Institute of Animal Reproduction and Food Research, Polish Academy of Sciences, Olsztyn, Poland.
Mariusz K
MK
Piskula
D000818:Animals; D001812:Blood-Brain Barrier / Q000187:drug effects; D002851:Chromatography, High Pressure Liquid; D004032:Diet / Q000662:veterinary; D004305:Dose-Response Relationship, Drug; D020719:Glucuronides / Q000097:blood; D023421:Models, Animal; D019697:Onions / Q000737:chemistry; D011794:Quercetin / Q000008:administration & dosage / Q000031:analogs & derivatives* / Q000097:blood / Q000134:cerebrospinal fluid* / Q000652:urine; D012756:Sheep; D053719:Tandem Mass Spectrometry
D020719:Glucuronides; C047368:3-methylquercetin; D011794:Quercetin
Brain barriers; Cerebrospinal fluid; Metabolites; Quercetin