Journal of Natural Medicines

, Volume 72, Issue 1, pp 181–191 | Cite as

Synergistic effect of baicalein, wogonin and oroxylin A mixture: multistep inhibition of the NF-κB signalling pathway contributes to an anti-inflammatory effect of Scutellaria root flavonoids

  • Tomofumi Shimizu
  • Nobuhiko Shibuya
  • Yuji Narukawa
  • Naohiro Oshima
  • Noriyasu Hada
  • Fumiyuki KiuchiEmail author
Original Paper


Scutellaria root, the root of Scutellaria baicalensis Georgi, is a crude drug used for inflammatory diseases. In our previous report, the combination of flavonoids contained in Scutellaria root have been found to inhibit PGE2 production more strongly than individual flavonoids. Here, to investigate the mechanism of the synergistic effect, we examined the effects of an equimolar mixture (F-mix) of baicalein (1), wogonin (2) and oroxylin A (3) on the production of PGE2 in LPS-treated J774.1 cells. Although 1 and 3 inhibited COX-2 activity, the F-mix showed no synergistic effect on COX-2 inhibition. Therefore, we investigated the steps leading to the activation of COX-2 protein. Compounds 13 and F-mix inhibited the expression of COX-2 protein. However, only 2 inhibited the expression of COX-2 mRNA among the flavonoids, and the F-mix showed no synergistic effect. Only 1 inhibited NF-κB translocation into the nucleus, and the F-mix showed no synergistic effect. Although 2 did not affect NF-κB translocation, it strongly inhibited NF-κB-dependent transcriptional activity, and the F-mix inhibited the activity slightly more than 2. Compounds 13 also inhibited NO production, and the F-mix showed a synergistic effect. However, the effects of each flavonoid on the expression of iNOS mRNA were not consistent with those on COX-2 mRNA. Because the flavonoids inhibit different steps in the production of PGE2 and NO, and their mixture did not show apparent synergistic effects in each step, we conclude that the synergistic effect of the flavonoid mixture reflects the total effect of the flavonoids inhibiting different steps in the NF-κB signalling pathway.


Scutellaria baicalensis Flavonoid Synergistic effect Prostaglandin E2 Inflammation Nuclear factor-kappa B 





Dulbecco’s modified Eagle’s medium


Foetal bovine serum


Glyceraldehyde 3-phosphate dehydrogenase


Interferon gamma


Inducible nitric oxide synthase


Interleukin-1 receptor-associated kinase


Interferon regulatory factor 3


Inhibitor of nuclear factor-kappa B


Janus kinase


N G-Monomethyl-l-arginine acetate




Mitogen-activated protein kinase


3-[4,5-Dimethylthiazol-2-yl]-2,5-diphenyl-tetrazolium bromide


Myeloid differentiation primary response gene 88


Nuclear factor-kappa B


Nitric oxide


Orthogonal projection to latent structure


Phosphate buffered saline


Principal component analysis




Polyvinylidene difluoride


Signal transducer and activator of transcription


Transforming growth factor beta-activated kinase 1


Transforming growth factor beta


Toll-like receptor


Tumour necrosis factor alpha


Tumour necrosis factor receptor-associated factor 6



This work was supported by JSPS KAKENHI grant number JP26460130, Keio Gijuku Academic Development Funds and MEXT-Supported Program for the Strategic Research Foundation at Private Universities. The authors thank Dr. Megumi Funakoshi-Tago for the valuable discussions.

Compliance with ethical standards

Conflict of interest

The authors declare that there is no conflict of interest.


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Copyright information

© The Japanese Society of Pharmacognosy and Springer Japan KK 2017

Authors and Affiliations

  1. 1.Faculty of PharmacyKeio UniversityTokyoJapan
  2. 2.Faculty of Pharmaceutical SciencesTokyo University of ScienceNodaJapan

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