title: A simple high-performance liquid chromatography (HPLC) method for the measurement of pyridoxal-5-phosphate and 4-pyridoxic acid in human plasma.
abstract: BACKGROUND
  Low concentration of plasma pyridoxal-5-phosphate (PLP) is associated with hyperhomocysteinemia and inflammation. Most methods for the measurement of plasma PLP require large specimen volume and involve the use of toxic reagents.
  
  
  METHODS
  We have developed a HPLC method for the measurement of PLP and 4-pyridoxic acid (4-PA) in plasma, which requires small specimen volume. The samples are prepared without adding any toxic reagents. Furthermore, we have examined whether intake of vitamin B6 affects the concentration of plasma PLP and 4-PA.
  
  
  RESULTS
  The coefficient of variation of the method was 6% and the recovery of the added vitamin in plasma was about 100%. The concentrations of plasma PLP and 4-PA in 168 healthy subjects were 40.6 (8.4-165.0) nmol/L, median and (range) and 17.5 (3.7-114.79) nmol/L, median and (range) respectively. In the multiple regression analyses, the concentration of plasma PLP was associated with the concentration of plasma 4-PA (p<0.0001), BMI, (p=0.02) and sex, (p=0.0008). The concentration of plasma 4-PA was associated with plasma PLP (p<0.0001), serum folate (p=0.004), smoking (p=0.03) and vitamin B6 intake (p=0.01).
  
  
  CONCLUSIONS
  The present method is suitable for large clinical studies for the measurement of plasma PLP and 4-PA. Our findings demonstrate that plasma 4-PA, BMI and sex are the major determinants of plasma PLP in healthy individuals.
authors.affiliation: Department of Natural Sciences, University of Agder, Kristiansand, Norway.
authors.forename: Rona
authors.initials: R
authors.lastname: Cabo
authors.affiliation: Department of Biochemistry, University of Technology and Life Sciences, Bydgoszcz, Poland.
authors.forename: Karolina
authors.initials: K
authors.lastname: Kozik
authors.affiliation: Department of Biochemistry, University of Technology and Life Sciences, Bydgoszcz, Poland.
authors.forename: Maciej
authors.initials: M
authors.lastname: Milanowski
authors.affiliation: Department of Nutrition and Public Health, University of Agder, Kristiansand, Norway.
authors.forename: Sigrunn
authors.initials: S
authors.lastname: Hernes
authors.affiliation: Department of Natural Sciences, University of Agder, Kristiansand, Norway.
authors.forename: Audun
authors.initials: A
authors.lastname: Slettan
authors.affiliation: National Institute of Public Health, Oslo, Norway.
authors.forename: Margaretha
authors.initials: M
authors.lastname: Haugen
authors.affiliation: William Harvey Research Institute, Queen Marry University of London, London, UK.
authors.forename: Shu
authors.initials: S
authors.lastname: Ye
authors.affiliation: Department of Nutrition, University of Oslo, Olso, Norway; Division of Cancer Medicine, Surgery and Transplantation, Oslo University Hospital, Olso, Norway.
authors.forename: Rune
authors.initials: R
authors.lastname: Blomhoff
authors.affiliation: Department of Natural Sciences, University of Agder, Kristiansand, Norway; Department of Nutrition, University of Oslo, Olso, Norway. Electronic address: mohammad.a.mansoor@uia.no.
authors.forename: M Azam
authors.initials: MA
authors.lastname: Mansoor
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D001774:Blood Chemical Analysis / Q000379:methods*; D002138:Calibration; D002851:Chromatography, High Pressure Liquid / Q000379:methods*; D005260:Female; D064368:Healthy Volunteers; D006801:Humans; D008297:Male; D008875:Middle Aged; D011732:Pyridoxal Phosphate / Q000097:blood*; D011735:Pyridoxic Acid / Q000097:blood*; D055815:Young Adult
chemical_list: D011735:Pyridoxic Acid; D011732:Pyridoxal Phosphate
keywords: HPLC; PLP and 4-PA; Vitamin B(6)