Hemodialysis Decreases the Concentration of Accumulated Plant Phenols in the Plasma of Patients on Maintenance Dialysis: Influence of Residual Renal Function Piotr Jan Nowak, 1 Radoslaw Wilk, 2 Anna Prymont-Przyminska, 3 Anna Zwolinska, 4 Agata Sarniak, 3 Anna Wlodarczyk, 5 Jeffrey de Graft-Johnson, 6 Beata Mamelka, 8 Anna Zasowska-Nowak, 7 Piotr Bartnicki, 2 Dariusz Nowak, 9 and Michal Nowicki 1 1 Department of Nephrology, Hypertension, and Kidney Transplantation, 2 Dialysis Center, Central Veterans Hospital, 3 Department of General Physiology, 4 Cell-to-Cell Communication Department, 5 Department of Sleep Medicine and Metabolic Disorders, 7 Palliative Medicine Laboratory, 8 Department of Laboratory Diagnostics and Clinical Biochemistry, 9 Department of Clinical Physiology, Medical University of Lodz, Lodz, Poland, and 6 Heart & Vascular Institute of North Florida, Tallahassee, FL, USA Abstract: Plant phenols may accumulate in end-stage kid- ney disease. The effect of hemodialysis on their plasma concentration remains poorly determined. Contingent on concentration, health-promoting or noxious effects occur; therefore, we assessed plasma concentration in hemodialyzed patients. In total, 21 maintenance hemodialyzed patients with diuresis < 500 mL per day (with oliguria), nine hemodialyzed patients with diuresis ≥ 500 mL per day (without oliguria) and 31 healthy volun- teers were included. Nine phenolic acids were identified with high-performance liquid chromatography and total polyphenol concentration was determined with the Folin– Ciocalteu method in pre- or post-hemodialysis plasma and pre- or intra-hemodialysis dialysate. The concentration of total polyphenols was 27% higher in pre-hemodialysis plasma than in that of controls (0.95 ± 0.18 mmol/L [P < 0.0001]). The concentration of total polyphenols was higher in patients with oliguria (1.01 ± 0.17) than in those without (0.84 ± 0.13 mmol/L), despite the former having more in- tense hemodialysis (Kt/V 1.29 ± 0.31 and 0.77 ± 0.25, re- spectively). Pre-hemodialysis phenolic acid concentration in patients undergoing dialysis exceeded reference values by 3 to 34 times (3-hydroxyphenylacetic acid and vanillic acid, respectively), from 0.69 (dihydrocaffeic acid) to 169.3 μmol/L (hippuric acid). The concentration of six phe- nolic acids (3-hydroxyhippuric, caffeic, dihydrocaffeic, hippuric, homovanillic, and vanillic acid) was 1.1 (homovanillic) to 11.3 (3-hydroxyhippuric) times higher in patients with oliguria than in those without. 4- hydroxyhippuric acid occurred more in the plasma of pa- tients with oliguria than in those without oliguria. A single hemodialysis session decreased total polyphenol concen- tration by 16% and phenolic acids from 30% (caffeic) to 58% (vanillic and 3-hydroxyphenylacetic acid) and these compounds appeared in the dialysate. The percentage de- crease (Δ%) of creatinine concentration correlated with the Δ% of total polyphenols and five phenolic acids (3- hydroxyphenylacetic, dihydrocaffeic, hippuric, homovanillic, and vanillic acid). Urea Δ% and Kt/V corre- lated only with the Δ% of homovanilic acid. The results demonstrate that phenols accumulate variably in hemodialyzed patients and are differently eliminated dur- ing hemodialysis. Residual renal function ensures a lower concentration of plasma phenols. Key Words: Concen- tration, Elimination, Hemodialysis, Phenolic acid, Polyphe- nol, Residual renal function. Phenolic compounds, which are widely distributed in plants and plant-derived products, are often found in human plasma. Foodstuffs such as tomatoes, broccoli, olives, plums, apples, berries, grapes, and currants, in addition to bran, cocoa, and beverages such as fruit juice, tea, and wine have been exten- sively investigated for their phenolic content (1–7). Diets rich in such foods provide simple and complex compounds like anthocyanins or procyanidins, which can be gradually degraded by colonic bacteria to form phenolic acids (1,8). They are subsequently Received March 2017; revised May 2017; accepted May 2017. Address correspondence and reprint requests to Dr Piotr Jan Nowak, Department of Nephrology, Hypertension, and Kidney Transplantation, Medical University of Lodz, Pomorska 251, 92- 213 Lodz, Poland. Email: piotr.nowak@umed.lodz.pl Therapeutic Apheresis and Dialysis 2017; ••(••):••–•• doi: 10.1111/1744-9987.12586 © 2017 International Society for Apheresis, Japanese Society for Apheresis, and Japanese Society for Dialysis Therapy 1 572 Therapeutic Apheresis and Dialysis 2017; 21(6):572–585 doi: 10.1111/1744-9987.12586 © 2017 International Society for Apheresis, Japanese Society for Apheresis, and Japanese Society for Dialysis Therapy