title: Allantoin in human plasma, serum, and nasal-lining fluids as a biomarker of oxidative stress: avoiding artifacts and establishing real in vivo concentrations.
abstract: Urate is the terminal product of purine metabolism in primates, including humans. Urate is also an efficient scavenger of oxidizing species and is thought to be an important antioxidant in human body fluids. Allantoin, the major oxidation product of urate, has been suggested as a candidate biomarker of oxidative stress because it is not produced metabolically. Although urate is converted to allantoin under strongly alkaline pH, such conditions have been used in the past to facilitate extraction of allantoin. We evolved a method for the determination of allantoin concentrations in human plasma and serum by gas chromatography-mass spectrometry without such artifact. With this method, we show that alkaline conditions do indeed cause breakdown of urate, leading to significant overestimation of allantoin concentration in human samples. By using our alternative method, serum samples from 98 volunteers were analyzed, and allantoin levels were found to be significantly lower than was previously reported. The in vivo utility and sensitivity of our method was further evaluated in human nasal-lining fluids. We were able to demonstrate an ozone-induced increase in allantoin, in the absence of increases in either ascorbate or glutathione oxidation products.
authors.affiliation: Centre for Life Sciences, Department of Biochemistry, Yong Loo Lin School of Medicine, National University of Singapore, Singapore.
authors.forename: Jan
authors.initials: J
authors.lastname: Gruber
authors.forename: Soon Yew
authors.initials: SY
authors.lastname: Tang
authors.forename: Andrew M
authors.initials: AM
authors.lastname: Jenner
authors.forename: Ian
authors.initials: I
authors.lastname: Mudway
authors.forename: Anders
authors.initials: A
authors.lastname: Blomberg
authors.forename: Annelie
authors.initials: A
authors.lastname: Behndig
authors.forename: Katherine
authors.initials: K
authors.lastname: Kasiman
authors.forename: Chung-Yung J
authors.initials: CY
authors.lastname: Lee
authors.forename: Raymond C S
authors.initials: RC
authors.lastname: Seet
authors.forename: Wenxia
authors.initials: W
authors.lastname: Zhang
authors.forename: Christopher
authors.initials: C
authors.lastname: Chen
authors.forename: Frank J
authors.initials: FJ
authors.lastname: Kelly
authors.forename: Barry
authors.initials: B
authors.lastname: Halliwell
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000481:Allantoin / Q000097:blood*; D016477:Artifacts; D015415:Biomarkers / Q000097:blood*; D001826:Body Fluids / Q000737:chemistry*; D018592:Cross-Over Studies; D004311:Double-Blind Method; D005260:Female; D008401:Gas Chromatography-Mass Spectrometry; D006801:Humans; D028421:Isoprostanes / Q000032:analysis; D008297:Male; D008875:Middle Aged; D009297:Nasal Mucosa / Q000378:metabolism*; D018384:Oxidative Stress
chemical_list: D015415:Biomarkers; D028421:Isoprostanes; D000481:Allantoin