Planta Med 2002; 68(10): 869-874
DOI: 10.1055/s-2002-34918
Original Paper
Pharmacology
© Georg Thieme Verlag Stuttgart · New York

Inducible Nitric Oxide Synthase Inhibitors of Chinese Herbs III. Rheum palmatum

Ching-Chiung Wang1 , Yi-Ju Huang1 , Lih-Geeng Chen2 , Lain-Tze Lee2 , Ling-Ling Yang1, 3
  • 1Graduate Institute of Pharmacognosy Science, Taipei Medical University, Taipei, Taiwan, R.O.C.
  • 2Graduate Institute of Biopharmaceutics, Life Science College, National Chiayi University, Chiayi, Taiwan, R.O.C.
  • 3Industrial Technology Research Institute, Hsinchu, Taiwan, R.O.C
Further Information

Publication History

Received: January 10, 2002

Accepted: May 18, 2002

Publication Date:
21 October 2002 (online)

Abstract

In this paper, the effects of bioactive compounds of Rheum palmatum L. on the inhibition of NO production from RAW 264.7 cells were explored. Seven main anthraquinone derivatives were isolated from the root of R. palmatum, and of these, emodin and rhein significantly inhibited nitrite production from lipopolysaccharide (LPS)-activated RAW 264.7 cells. The IC50 values for inhibition of nitrite production by emodin and rhein were 60.7 and 67.3 μM, respectively. After iNOS enzyme activity was stimulated by LPS for 12 h, treatment with emodin or rhein at 20 μg/ml for 18 h did not significantly inhibit NO production. The data show that the inhibitory activity of emodin and rhein is not due to direct inhibition of iNOS enzyme activity. However, expression of iNOS and the COX-2 protein was inhibited by emodin in LPS-activated RAW 264.7 cells, and PGE2 production was reduced. Rhein also inhibited LPS-induced iNOS protein expression, but not COX-2 or PGE2 production. On the other hand, inhibition effects on NO production from RAW 264.7 cells were enhanced and cytotoxic effects decreased by co-treatment with emodin and rhein. In conclusion, emodin and rhein are major iNOS inhibitors of R. palmatum and may possibly serve as bioactive substances for anti-inflammation effects.

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Prof. Ling-Ling Yang

Graduate Institute of Biopharmaceutics

Life Science College

National Chiayi University

300 University Road

Chiayi 600

Taiwan, R.O.C.

Email: llyang@ncyu.edu.tw

Phone: +886-5-2717930

Fax: +886-5-2717931