Bioassay-guided isolation of anti-inflammatory components from the root of Rehmannia glutinosa and its underlying mechanism via inhibition of iNOS pathway

J Ethnopharmacol. 2012 Oct 11;143(3):867-75. doi: 10.1016/j.jep.2012.08.012. Epub 2012 Aug 22.


Ethnopharmacological relevance: 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).

Aim of study: 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.

Materials and 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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Anti-Inflammatory Agents / pharmacology*
  • Biological Assay
  • Cell Line
  • Cyclooxygenase 2 Inhibitors / pharmacology
  • Dinoprostone / metabolism
  • Drugs, Chinese Herbal / pharmacology*
  • Interleukin-6 / antagonists & inhibitors
  • Interleukin-6 / metabolism
  • Lipopolysaccharides
  • Mice
  • Nitric Oxide / metabolism
  • Nitric Oxide Synthase Type II / antagonists & inhibitors
  • Plant Extracts / pharmacology*
  • Plant Roots
  • Rehmannia*


  • Anti-Inflammatory Agents
  • Cyclooxygenase 2 Inhibitors
  • Drugs, Chinese Herbal
  • Interleukin-6
  • Lipopolysaccharides
  • Plant Extracts
  • rehmapicrogenin
  • Nitric Oxide
  • Nitric Oxide Synthase Type II
  • Nos2 protein, mouse
  • Dinoprostone