ABSTRACT
Objective To develop a solid phase extraction and Folin-Ciocalteu method for the measurement of total polyphenols in urine samples.Methods From a group of individuals attending an annual physical examination at Beijing hospital, 123 healthy volunteers (52 males and 71 females, ranging in age from 18 to 81 years ) were recruited during the period from December 2013 to April 2014.Urine samples were stored in 0.5%HCl at -80 ℃.For analysis, samples were applied to the Plexa PAX solid phase extraction cartridge, to purity the polyphenols through washing, evaporating and reconstituting.Total polyphenols were measured by Folin-Ciocalteu colorimetric assay, calculated by gallic acid standard curve, and corrected by urine creatinine concentrations.The relationship between total polyphenols and fruits and vegetable intake and cardiovascular disease risk factors were analyzed. Results Gallic acid standard solution and urine samples were stable in 0.5% HCl for 48 h at RT and 7days at 4 ℃, respectively.The PAX cartridge effectively eliminated the possible interfere materials in urine and had better recovery for most of the polyphenol types.The inter assay and total CVs for the measurement of total polyphenols were 2.7%-3.8% and 2.4%-4.6 %, respectively.Total polyphenol concentrations of 123 healthy subjects were 114.13(82.97-146.70) mg GAE/g Crea.Total polyphenol levels positively correlated with both HDL-C (r=0.194, P=0.032) and apoAI (r=0.312,P<0.001), and negatively correlated with serum uric acid levels(r=-0.220,P=0.014).Conclusions We established a measurement of total polyphenols in urine samples using solid phase extraction and Folin-Ciocalteu method.This simple, precise method reliable and may be use to assess dietary polyphenols intake.