title: Bioassay-guided isolation of anti-inflammatory components from the root of Rehmannia glutinosa and its underlying mechanism via inhibition of iNOS pathway.
abstract: BACKGROUND
  The root of Rehmannia glutinosa (RR) is commonly used to reduce inflammation in various traditional Chinese herbal formulae; however, little is known regarding its active component(s).
  
  
  OBJECTIVE
  The objective of the present study was to examine the active component(s) responsible for the anti-inflammatory activity of RR via anti-nitric oxide production assay-guided fractionation; and the underlying anti-inflammatory mechanism of action of such component(s) was further investigated.
  
  
  METHODS
  Anti-nitric oxide (NO) activities with lipopolysaccharides (LPS)-stimulated RAW264.7 murine macrophages was used as screening platform. Gene, protein and inflammatory mediators' expression were also studied using real-time PCR, western blotting and ELISA, respectively.
  
  
  RESULTS
  Using anti-NO assay-guided fractionation, sub-fraction C3 (from 31.25 to 62.5 μg/ml, p=0.001 to 0.01) possessed 100-fold more potent anti-inflammatory effect than that of the aqueous extract of RR. Characterization of C3 showed that the anti-inflammatory effect could be partly due to the presence of rehmapicrogenin, which could significantly inhibit NO production (p<0.001). C3 was further demonstrated in blocking inflammation by inhibiting gene (p<0.001) and protein expression of inducible NO synthase (iNOS) dose-dependently. Besides, C3 also significantly inhibited the production of prostaglandin E(2) (p<0.001 to 0.01), IL-6 (p<0.001 to 0.05) and COX-2 (p<0.05).
  
  
  CONCLUSIONS
  Rehmapicrogenin was, for the first time, shown to possess nitric oxide inhibitory activities. Bioassay-guided fractionation demonstrated that rehmapicrogenin-containing subfraction C3 exhibited potent anti-inflammatory effect by inhibiting iNOS, COX-2 and IL-6, while rehmapicrogenin was only partially responsible for the anti-inflammatory effect of RR.
authors.affiliation: Institute of Chinese Medicine, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, China.
authors.forename: Cheuk-Lun
authors.initials: CL
authors.lastname: Liu
authors.forename: Ling
authors.initials: L
authors.lastname: Cheng
authors.forename: Chun-Hay
authors.initials: CH
authors.lastname: Ko
authors.forename: Chun-Wai
authors.initials: CW
authors.lastname: Wong
authors.forename: Wai-Hing
authors.initials: WH
authors.lastname: Cheng
authors.forename: David Wing-Shing
authors.initials: DW
authors.lastname: Cheung
authors.forename: Ping-Chung
authors.initials: PC
authors.lastname: Leung
authors.forename: Kwok-Pui
authors.initials: KP
authors.lastname: Fung
authors.forename: Clara
authors.initials: C
authors.lastname: Bik-San Lau
mesh_terms: D000818:Animals; D000893:Anti-Inflammatory Agents / Q000494:pharmacology*; D001681:Biological Assay; D002460:Cell Line; D052246:Cyclooxygenase 2 Inhibitors / Q000494:pharmacology; D015232:Dinoprostone / Q000378:metabolism; D004365:Drugs, Chinese Herbal / Q000494:pharmacology*; D015850:Interleukin-6 / Q000378:metabolism; D008070:Lipopolysaccharides; D051379:Mice; D009569:Nitric Oxide / Q000378:metabolism; D052247:Nitric Oxide Synthase Type II / Q000037:antagonists & inhibitors; D010936:Plant Extracts / Q000494:pharmacology*; D018517:Plant Roots; D032267:Rehmannia; D000093242:Interleukin-6 Inhibitors
chemical_list: D000893:Anti-Inflammatory Agents; D052246:Cyclooxygenase 2 Inhibitors; D015232:Dinoprostone; D004365:Drugs, Chinese Herbal; D015850:Interleukin-6; D008070:Lipopolysaccharides; D009569:Nitric Oxide; D052247:Nitric Oxide Synthase Type II; D010936:Plant Extracts; D000093242:Interleukin-6 Inhibitors; C579045:rehmapicrogenin; C496317:Nos2 protein, mouse