title: Addition of strawberries to the usual diet increases postprandial but not fasting non-urate plasma antioxidant activity in healthy subjects.
abstract: Strawberries can augment plasma antioxidant activity, but this may be confounded by selection of methods, time of blood sampling and concomitant dietary restrictions. We examined the effect of strawberry consumption on ferric reducing ability (FRAP) and 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity (DPPH-test) of native and non-urate plasma in healthy subjects on their usual diet. Eleven subjects consumed strawberries (500 g daily) for 9 days. Fasting and 3-h postprandial plasma and 24-h urine collection were obtained before, during and after strawberry course for FRAP, DPPH-test and polyphenols determination. Fifteen subjects served as a control in respect to plasma antioxidant activity changes and effect of 300 mg of oral ascorbate. First, 5th and 9th strawberry dose increased 3-h postprandial DPPH-test by 17.4, 17.6 and 12.6%, and FRAP by 15.5, 25.6 and 21.4% in comparison to fasting values in non-urate plasma (p<0.05). In native plasma only a trend was observed to higher postprandial values for both tests. Strawberries increased urinary urolithin A and 4-hydroxyhippuric acid whereas plasma polyphenols were stable. No changes of FRAP and DPPH-test were noted in controls and after ascorbate intake. Strawberries transiently increased non-urate plasma antioxidant activity but this cannot be attributed to direct antioxidant effect of polyphenols and ascorbate.
authors.affiliation: Department of General Physiology, Medical University of Lodz, Lodz, Poland.
authors.forename: Anna
authors.initials: A
authors.lastname: Prymont-Przyminska
authors.affiliation: Department of Sleep Medicine and Metabolic Disorders, Medical University of Lodz, Lodz, Poland.
authors.forename: Piotr
authors.initials: P
authors.lastname: Bialasiewicz
authors.affiliation: Cell-to-Cell Communication Department, Medical University of Lodz, Lodz, Poland.
authors.forename: Anna
authors.initials: A
authors.lastname: Zwolinska
authors.affiliation: Department of General Physiology, Medical University of Lodz, Lodz, Poland.
authors.forename: Agata
authors.initials: A
authors.lastname: Sarniak
authors.affiliation: Department of Sleep Medicine and Metabolic Disorders, Medical University of Lodz, Lodz, Poland.
authors.forename: Anna
authors.initials: A
authors.lastname: Wlodarczyk
authors.affiliation: Fruit Storage and Processing Department, Division of Pomology, Research Institute of Horticulture, Skierniewice, Poland.
authors.forename: Jaroslaw
authors.initials: J
authors.lastname: Markowski
authors.affiliation: Fruit Storage and Processing Department, Division of Pomology, Research Institute of Horticulture, Skierniewice, Poland.
authors.forename: Krzysztof P
authors.initials: KP
authors.lastname: Rutkowski
authors.affiliation: Department of Clinical Physiology, Medical University of Lodz, Lodz, Poland.
authors.forename: Dariusz
authors.initials: D
authors.lastname: Nowak
keywords: bioactive compounds; dietary antioxidants; phenolics; plasma antioxidant activity; strawberry; supplements and functional foods