title: Discovery of glycyrrhetinic acid as an orally active, direct inhibitor of blood coagulation factor xa.
abstract: BACKGROUND
  Factor Xa (FXa) plays an important role in blood coagulation. This study investigated glycyrrhetinic acid, a small molecule derived from Chinese herbs, and whether it has a direct inhibitory effect on FXa to display its anticoagulant activity.
  
  
  METHODS
  Enzyme activities of FXa, plasmin, trypsin and thrombin, inhibition of FXa enzyme kinetics and plasma clotting time by glycyrrhentinic acid were performed in vitro. A rat tail-bleeding model and a rat venous stasis model were also used to evaluate in vivo tail-bleeding time and thrombus formation, respectively.
  
  
  RESULTS
  Glycyrrhetinic acid in vitro directly inhibited FXa uncompetitivly with IC50 of 32.6 ± 1.24 μmol/L, and displayed 2-, 14- and 20-fold selectivity for FXa when compared to plasmin, thrombin and trypsin, respectively. The plasma clotting time was increased in a dose-dependent manner. The prothrombin time doubled (PT2), when the concentration of glycyrrhetinic acid reached 2.02 mmol/L. During in vivo experiments intragastric administration of glycyrrhetinic acid caused a dose-dependent reduction in thrombus weight on the rat venous stasis model (all P<0.05). 50 mg/kg glycyrrhetinic acid resulted in 34.8% of venous thrombus weight lost, compared to the control. In addition, 200, 300 and 400 mg/kg doses of glycyrrhetinic acid caused a moderate hemorrhagic effect in the rat tail-bleeding model by prolonging bleeding time 1.1-, 1.5- and 1.9-fold compared to the control, respectively.
  
  
  CONCLUSIONS
  Glycyrrhetinic acid is a direct inhibitor of FXa that is effective by oral administration, and with further research could be used to treat blood coagulation disorders.
authors.affiliation: School of Pharmacy, Nanjing University of Chinese Medicine, Nanjing 210046, China; School of Pharmacy, Hainan Medical University, Haikou 571101, China.
authors.forename: Lilong
authors.initials: L
authors.lastname: Jiang
authors.affiliation: School of Pharmacy, Nanjing University of Chinese Medicine, Nanjing 210046, China.
authors.forename: Qiong
authors.initials: Q
authors.lastname: Wang
authors.affiliation: School of Pharmacy, Nanjing University of Chinese Medicine, Nanjing 210046, China.
authors.forename: Shu
authors.initials: S
authors.lastname: Shen
authors.affiliation: Department of Phytochemistry, Jiangsu Provincial Institute of Traditional Chinese Medicine, Nanjing 210028, China.
authors.forename: Tongshu
authors.initials: T
authors.lastname: Xiao
authors.affiliation: School of Pharmacy, Hainan Medical University, Haikou 571101, China; Department of Phytochemistry, Jiangsu Provincial Institute of Traditional Chinese Medicine, Nanjing 210028, China. Electronic address: liyoubinli@sohu.com.
authors.forename: Youbin
authors.initials: Y
authors.lastname: Li
mesh_terms: D000284:Administration, Oral; D000818:Animals; D000925:Anticoagulants / Q000494:pharmacology*; D004195:Disease Models, Animal; D015951:Factor Xa / Q000378:metabolism*; D006034:Glycyrrhetinic Acid / Q000494:pharmacology*; D006470:Hemorrhage / Q000188:drug therapy; D008297:Male; D011517:Prothrombin Time; D051381:Rats; D017208:Rats, Wistar; D013623:Tail / Q000098:blood supply; D020246:Venous Thrombosis / Q000097:blood / Q000188:drug therapy*
chemical_list: D000925:Anticoagulants; D015951:Factor Xa; D006034:Glycyrrhetinic Acid
keywords: Anticoagulation; Blood Coagulation Factor Xa; Glycyrrhiza glabra; Prothrombin Time (PT); Thrombosis