Planta Med 2006; 72(1): 28-33
DOI: 10.1055/s-2005-873149
Original Paper
Pharmacology
© Georg Thieme Verlag KG Stuttgart · New York

Pheophorbide a, a Major Antitumor Component Purified from Scutellaria barbata, Induces Apoptosis in Human Hepatocellular Carcinoma Cells

Judy Yuet-Wa Chan1 , Patrick Ming-Kuen Tang1 , Po-Ming Hon2 , Shannon Wing-Ngor Au1 , Stephen Kwok-Wing Tsui1 , Mary Mui-Yee Waye1 , Siu-Kai Kong1 , Thomas Chung-Wai Mak2 , 3 , Kwok-Pui Fung1 , 2
  • 1Department of Biochemistry, The Chinese University of Hong Kong, Shatin, N.T., Hong Kong, China
  • 2Institute of Chinese Medicine, The Chinese University of Hong Kong, Shatin, N.T., Hong Kong, China
  • 3Department of Chemistry, The Chinese University of Hong Kong, Shatin, N.T., Hong Kong, China
Further Information

Publication History

Received: December 29, 2004

Accepted: June 22, 2005

Publication Date:
10 November 2005 (online)

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Abstract

Scutellaria barbata has long been used as a Chinese medicine for the treatment of liver diseases such as hepatitis and hepatocellular carcinoma. In the present study, a bioassay-guided method was used to isolate the most active components from Scutellaria barbata. The anti-proliferative effects on human hepatoma HepG2 and Hep3B cells of each fraction at every stage of the purification were monitored. An active component, which is 97 % pure by high performance liquid chromatographic analysis, was isolated. Based on nuclear magnetic resonance (NMR) and mass spectrophotometric (MS) analysis, this active component was identified to be pheophorbide a (C35H36N4O5). Mechanistic studies showed that pheophorbide a induced apoptosis in Hep3B cells, a viral-induced hepatoma cell line. However, it was found to be non-toxic in normal human liver cells WRL-68. DNA fragmentation, sub-G1 cell cycle arrest, as well as suppression of the anti-apoptotic protein Bcl-2, release of cytochrome c to the cytosol, and activation of pro-caspase 3 and pro-caspase 9 were observed when Hep3B cells were treated with 40 μg/mL (i. e., 67.5 μM) pheophorbide a for 48 hours. In conclusion, this is the first report describing the isolation of pheophorbide a from Scutellaria barbata using a bioassay-guided isolation method. The anti-proliferative activity and possible mechanisms of action of pheophorbide a on hepatoma Hep3B cells are also discussed.