title: Conjugated metabolites represent the major circulating forms of Abelmoschus manihot in vivo and show an altered pharmacokinetic profile in renal pathology.
abstract: BACKGROUND
  The nephron-protective efficacy of Abelmoschus manihot (Linn.) Medicus (Malvaceae) has been proved by randomized controlled clinical trial.
  
  
  OBJECTIVE
  Flavonoids are main active components of A. manihot, which can be transformed into glucuronide/sulfate conjugates in vivo. Exploring the pharmacokinetic profile of these conjugates is necessary to further elucidate the mechanism of action.
  
  
  METHODS
  Flavonoid fraction of A. manihot (FFA) was extracted from A. manihot flower with ethanol. FFA (400 mg/kg) was orally given to normal rats and chronic kidney disease (CKD) model rats. Blood samples were collected at 5, 15, 30, 45, 60, 90, 120, 240, 360, and 720 min after administration. The plasma concentrations of quercetin and isorhamnetin glucuronide/sulfate conjugates were analyzed by UPLC-MS/MS.
  
  
  RESULTS
  In normal rats, AUC of quercetin-glucuronide conjugates, isorhamnetin-glucuronide conjugates, quercetin-sulfate conjugates, and isorhamnetin-sulfate conjugates was 459.45 ± 192.70, 1153.01 ± 697.04, 417.81 ± 220.31, and 2475.19 ± 1085.22 μmol h/L, respectively. While AUC of quercetin and isorhamnetin was 5.47 ± 2.54 and 30.73 ± 25.95 μmol h/L. AUC of the glucuronide-sulfate conjugates of quercetin and isorhamnetin is 125-times higher than that of aglycone (quercetin and isorhamnetin), showing that glucuronide/sulfate conjugates represent the major circulating forms of A. manihot flavonoid in vivo. AUC of isorhamnetin-glucuronide conjugates and quercetin-sulfate conjugates was 719.65 ± 619.22 and 275.49 ± 1 60.95 μmol h/L, indicating that less conjugated metabolites were formed in CKD rats compared with normal rats. The ratio of AUCglucuronide/sulfate/AUCaglycone decreased from 125 to 104, which implied the impaired phase II metabolism ability in CKD rat.
  
  
  CONCLUSIONS
  Glucuronide-sulfate conjugates provide an important clue for further elucidating the activity of conjugated metabolites and their relationship with the nephroprotective efficacy of A. manihot. It is necessary to take caution when extrapolating pharmacokinetics parameters from healthy animals in designing pharmacological studies.
authors.affiliation: a Jiangsu Collaborative Innovation Center of Chinese Medicinal Resources Industrialization, National and Local Collaborative Engineering Center of Chinese Medicinal Resources Industrialization and Formulae Innovative Medicine, Nanjing University of Chinese Medicine , Nanjing , China.
authors.forename: Jianming
authors.initials: J
authors.lastname: Guo
authors.affiliation: a Jiangsu Collaborative Innovation Center of Chinese Medicinal Resources Industrialization, National and Local Collaborative Engineering Center of Chinese Medicinal Resources Industrialization and Formulae Innovative Medicine, Nanjing University of Chinese Medicine , Nanjing , China.
authors.forename: Leyue
authors.initials: L
authors.lastname: Du
authors.affiliation: a Jiangsu Collaborative Innovation Center of Chinese Medicinal Resources Industrialization, National and Local Collaborative Engineering Center of Chinese Medicinal Resources Industrialization and Formulae Innovative Medicine, Nanjing University of Chinese Medicine , Nanjing , China.
authors.forename: Erxin
authors.initials: E
authors.lastname: Shang
authors.affiliation: a Jiangsu Collaborative Innovation Center of Chinese Medicinal Resources Industrialization, National and Local Collaborative Engineering Center of Chinese Medicinal Resources Industrialization and Formulae Innovative Medicine, Nanjing University of Chinese Medicine , Nanjing , China.
authors.forename: Ting
authors.initials: T
authors.lastname: Li
authors.affiliation: a Jiangsu Collaborative Innovation Center of Chinese Medicinal Resources Industrialization, National and Local Collaborative Engineering Center of Chinese Medicinal Resources Industrialization and Formulae Innovative Medicine, Nanjing University of Chinese Medicine , Nanjing , China.
authors.forename: Yang
authors.initials: Y
authors.lastname: Liu
authors.affiliation: a Jiangsu Collaborative Innovation Center of Chinese Medicinal Resources Industrialization, National and Local Collaborative Engineering Center of Chinese Medicinal Resources Industrialization and Formulae Innovative Medicine, Nanjing University of Chinese Medicine , Nanjing , China.
authors.forename: Dawei
authors.initials: D
authors.lastname: Qian
authors.affiliation: a Jiangsu Collaborative Innovation Center of Chinese Medicinal Resources Industrialization, National and Local Collaborative Engineering Center of Chinese Medicinal Resources Industrialization and Formulae Innovative Medicine, Nanjing University of Chinese Medicine , Nanjing , China.
authors.forename: Yuping
authors.initials: Y
authors.lastname: Tang
authors.affiliation: a Jiangsu Collaborative Innovation Center of Chinese Medicinal Resources Industrialization, National and Local Collaborative Engineering Center of Chinese Medicinal Resources Industrialization and Formulae Innovative Medicine, Nanjing University of Chinese Medicine , Nanjing , China.
authors.forename: Jinao
authors.initials: J
authors.lastname: Duan
mesh_terms: D028483:Abelmoschus; D000818:Animals; D005419:Flavonoids / Q000097:blood / Q000302:isolation & purification / Q000493:pharmacokinetics; D035264:Flowers; D007668:Kidney / Q000187:drug effects / Q000378:metabolism* / Q000473:pathology*; D008297:Male; D010936:Plant Extracts / Q000097:blood* / Q000302:isolation & purification / Q000493:pharmacokinetics*; D051381:Rats; D017207:Rats, Sprague-Dawley
chemical_list: D005419:Flavonoids; D010936:Plant Extracts
keywords: Chronic kidney disease; glucuronide/sulfate conjugates; uremic toxins