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

• Published in: Journal of ethnopharmacology Vol. 143; no. 3; pp. 867 - 875
• Main Authors: Liu, Cheuk-Lun, Cheng, Ling, Ko, Chun-Hay, Wong, Chun-Wai, Cheng, Wai-Hing, Cheung, David Wing-Shing, Leung, Ping-Chung, Fung, Kwok-Pui, Bik-San Lau, Clara
• Format: Journal Article
• Language: English
• Published: Ireland Elsevier Ireland Ltd 11-10-2012
• Subjects: Animals; Anti-inflammation; anti-inflammatory activity; Anti-Inflammatory Agents - pharmacology; Bioassay-guided fractionation; Biological Assay; Cell Line; Cyclooxygenase 2 Inhibitors - pharmacology; Cyclooxygenase-2; Dinoprostone - metabolism; Drugs, Chinese Herbal - pharmacology; enzyme-linked immunosorbent assay; fractionation; genes; Inducible nitric oxide synthase; inflammation; Interleukin-6; Interleukin-6 - antagonists & inhibitors; Interleukin-6 - metabolism; Lipopolysaccharides; macrophages; mechanism of action; Mice; Nitric oxide; Nitric Oxide - metabolism; Nitric Oxide Synthase Type II - antagonists & inhibitors; Plant Extracts - pharmacology; Plant Roots; Prostaglandin E2; prostaglandins; protein synthesis; quantitative polymerase chain reaction; Rehmannia; Rehmannia glutinosa; Rehmapicrogenin; screening; Western blotting; Bioassay-guided fractionation; Rehmapicrogenin; Inducible nitric oxide synthase; Nitric oxide; Prostaglandin E2; Rehmannia glutinosa; Cyclooxygenase-2; Anti-inflammation; Interleukin-6
• ISSN: 0378-8741; 1872-7573
• DOI: 10.1016/j.jep.2012.08.012

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.
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.
Using anti-NO assay-guided fractionation, sub-fraction C3 (from 31.25 to 62.5μg/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 E2 (p<0.001 to 0.01), IL-6 (p<0.001 to 0.05) and COX-2 (p<0.05).
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.
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