title: Pilot walnut intervention study of urolithin bioavailability in human volunteers.
abstract: A pilot intervention study was conducted in human volunteers (n = 4) to establish the bioavailability of urolithins, which are the terminal end-products of ellagitannin metabolism by the gastrointestinal microflora. Biospecimens (blood, feces, and urine) along with urolithins purified therefrom were analyzed for their antioxidant capacity in a range of in vitro assays. Urolithin metabolites were identified and quantitated in the biospecimens by negative ion mode HPLC-ESI-MS analysis. The data in this pilot study show that the metabolism of ellagitannins in the four volunteers gave rise to a diverse profile and a highly variable concentration of urolithins in urine. The concentration of glucuronidated urolithins in blood and urine did not correlate with antioxidant capacity. However, the antioxidant capacity of urine, but not plasma biospecimens, was highly correlated with uric acid concentration. The antioxidant capacity of fecal extracts correlated positively with the concentration of urolithin D in both the DPPH and FRAP assays, but not in the ORAC assay, which was entirely consistent with the in vitro assays for pure urolithin D.
authors.affiliation: Division of Preventive Oncology, National Center for Tumor Diseases , Im Neuenheimer Feld 460, 69120 Heidelberg, Germany.
authors.forename: Beate
authors.initials: B
authors.lastname: Pfundstein
authors.forename: Roswitha
authors.initials: R
authors.lastname: Haubner
authors.forename: Gerd
authors.initials: G
authors.lastname: Würtele
authors.forename: Nicole
authors.initials: N
authors.lastname: Gehres
authors.forename: Cornelia M
authors.initials: CM
authors.lastname: Ulrich
authors.forename: Robert W
authors.initials: RW
authors.lastname: Owen
mesh_terms: D000328:Adult; D000975:Antioxidants / Q000032:analysis / Q000378:metabolism; D003374:Coumarins / Q000097:blood / Q000378:metabolism* / Q000652:urine; D005243:Feces / Q000737:chemistry; D005260:Female; D064368:Healthy Volunteers; D006801:Humans; D047348:Hydrolyzable Tannins / Q000097:blood / Q000378:metabolism* / Q000652:urine; D031324:Juglans / Q000378:metabolism*; D008297:Male; D009754:Nuts / Q000378:metabolism; D010865:Pilot Projects; D010936:Plant Extracts / Q000097:blood / Q000378:metabolism* / Q000652:urine
chemical_list: D000975:Antioxidants; D003374:Coumarins; D047348:Hydrolyzable Tannins; D010936:Plant Extracts; C000595064:urolithin B; C588364:urolithin C; C000595063:urolithin D; C026423:3,8-dihydroxy-6H-dibenzo(b,d)pyran-6-one
keywords: DPPH assay; FRAP assay; ORAC assay; ellagitannins; uric acid; urolithins; walnuts